Everything About Tuning The 2.25 Petrol Engine – ACR, Turner & others perspective

engine2.25petrolWarning: Long article but worth it..! There are a lot of information about how we upgrade our old engine… some says.. : drop in the 2.5 cam, milled the head by 0.02 inch, ported and polish etc etc.. all is good advise but I read this discussion (or debate) with great interest and decided to put it here in case we need  reference lets start (I deleted conversation that are irrelevant), and unfortunately, I can not see the poster names unless it stated at the end of the post.

Someone: I think that these engines have a specified max rev limit of 4600. Though going over 4000 for anything short of a few seconds is probably not a good idea. My tachometer has the occasional misbeat but in no way does it wander like yours does. If its something to do with the ignition and not a bad connection it’ll show up on a vacuum guage as well, they’re cheap, easy to fit and very useful.

Roland (ACR): We set the Power Plus engine red line at 5200RPM this will give plenty of safety margin as they will run to 5700 on an intermittent basis with no problems. There is little to be gained by running much over 4800 as the power falls off rapidly over this point. However if you enjoy using the power e.g. racing rush hour traffic, off road competition etc it is useful to be able to run past maximum power so that the engine drops into a more favourable part of the power band on changing up a gear as the spacing between gear ratios on the 4 speed box is large. Regarding oil temperature the red line is around 250 however Mobil 1 will work safely well beyond that . We would keep the 250 as the upper maximum it is very unlikely even desert temperatures will push the temperature this high.

Turner: Personally I cannot abide engines that have to be revved to perform and prefer to tune for low speed torque. It is interesting how people always get exited by great bhp claims that can only be produced under controlled conditions and never mention torque output. Not realising that the higher bhp figures can only be achieved at very high rpm and would not be comfortable driving under these circumstances. High bhp will not normally be found at low speed making the torque output of the engine far more relevant. Torque is a reading taken at much lower rpm (approx 2750), whereas bhp being a product of multiplication increases the higher the engine is revved.

If anyone has stood next to an engine running on a dynomometer at 4000 rpm pulling maximum bhp, after a few seconds you feel like wanting to take two steps backwards. Visitors to our factory watching this type of test never looked particularly comfortable observing this type of test. Most stated that they did not realise this was how maximum bhp was measured. Mechanical and thermal loads rise rapidly the higher the rpm. The increase in loading is not linear. Engines used under race conditions are usually rebuilt after only a few hours use and can very often show wear consistent with high rpm and high loadings.

The 2.25 Land Rover engines have heavy rotating and reciprocating components and most are not built with bearings suitable for race conditions. Fortunately 2.25 petrol engines are a relatively cheap commodity and therefore do not represent a major financial risk to most people. A major failure in a lot of cases can be regarded as fun by the mechanically competent or those prepared to wreck cheap used engines, but a major set back for those who have to pay others to fix their disasters. Heavy vehicles benefit from more torque low down the rev range, not high bhp. I have had various dealings with people in the racing industry over the years, most would trade high bhp for midspeed grunt and driveability.

Someone: RPR, the max rev limit I can see in Land Rover’s official documentation is 4,250rpm. RolandACR, no matter how hard you try you’ll never get a Land Rover to be a Fiesta XR2 which seems to be what your conversions are all about. R Turner, couldn’t agree more

ACR : In reply to Richard Turners comments. The whole purpose of our Power Plus modifications is to produce torque! Here are the facts. On our latest 2.8 engine upgrade 120Ib.ft @ 980RPM (this is more than the standard 2.25 produces at its peak) 177Ib.ft @ 2300RPM. 117BHP @4100RPM as you can see these figures speak for themselves, more torque at 1000RPM lower down than 3.5V8!
Regarding the 2.25 to produce power it is wrong to state that this engine will become unreliable if fitted with our Power Plus modifications. In fact some of our early installatins have completed over 100,000 miles. Our modifications have an excellent reliability record confirmed by customer testimonials and product surveys. Our products are carefully designed and tested prior to release lets face it off road and on the 2.25 in standard form ia an under powered slug especially in heavy vehicles such as 109 station wagon where in modern traffic they are quite unsuitable. It is in these situations that the Power Plus system excels. By the way I never did like the Fiesta XR2, are there any still left out there?

Turner : Roland, Where did anybody discuss a 2.8 hybrid engine? The purpose of the discussion was to debate the reliability issues concerning normal day to day used engines having covered relatively high mileages from new and which are used for normal motoring in order that LR owners can better understand the implications of modifying their existing engine. The comments concerning claimed performance output of some non standard 2.8 modified engine are completely irrelevant to the argument.

Any modification that affects power output or fundamentally interferes with mixtures or compression ratio outside of the original manufacturers intentions will affect reliablility and life expectancy. I have discussed this issue at length over the years with component manufacturers and independent engineers concerned with examination of failed engines of all makes and types and indeed people in the performance industy. This is fact. Unfortunately none of the Land Rover magazines have sofar chosen to conduct independent trials of aftermarket products to verify whether the claims made are true or otherwise. This does little to assist the buying public as to what represents value for money.

ACR: Richard It is wrong to say that independant tests and magazine articles ahve not been conducted. Please refer to LRO Carl Rogerson Oct’97, LRW Matt Ross June’99 & Steve Anderson Nov’00, LRM Mike Yardley Apr’99. These articles are independant proof that our modifications are all about torque and driveability. Everyone must surely agree that Series vehicles need more power and that it is preferable to improve the original than fit some unsuitable conversion. Thankfully the 2.25 is so understressed the safety margins from the reliability point of view are enormous, even in tuned form infact used as a supercharged race engine, as we do for use in international rallying and off road racing – Yes it is competative against ex. worl rally Subaru Imprezza and Mitsubishi Evo. The standard 2.25 components within that engine withstand the very heavy loadings reliability and without strip down or rebuild from one season to the next.
It seems to me that you simply cannot accept that our product is successful and use occasions such as this simply to attack ACR. One thing I do agree though is that a controlled trial of ACR Power Plus engines against conversions and other aftermarket products would indeed make a very interesting magazine article.

Turner: Roland, I am not attacking your product. I merely re-iterate that the purpose of the debate is to establish whether it is sensible to rev a 30 yr old engine in excess of 5000rpm, which you state is safe and will not cause shortening of the life expectancy.

Keep in mind that the life expectancy of a new 2.25 petrol engine is in the region of 3 to 400.000 miles. The question is – will a 2.25 petrol still achieve 3 to 400.000 miles if revved to in excess of 5000rpm on a regular basis or if it has allready covered many miles. At this point it would be useful to mention our experience of examining failed military engines. These engines are normally unsympathetically driven and suffer failures not normally seen in civilian used engines. It is not uncommon to see broken pistons, loose small end bushes and other types of damage consistent with high speed operation. The statement that an engine can be safely revved to in excess of 5000 revs on a regular basis without risk is untrue.

Road tests carried out be magazines are not independent proof or verification of a suppliers claims and we would include ourselves as far as this is concerned.Many articles have been written over the years about Turner Engineering. The only tests that are truly valid on performance related products would be tests carried out by an independent test house using calibrated and computerised equipment, comprehensive gas analysis equipment and carried out by independent unbiased engineers who do not receive payment for advertising.

We as a company have deliberately avoided non standard performance products due to the high cost of employing independent consultants to develop products for which there is a limited market. To go it alone as you have done is a brave move and I admire you for that. If what you claim is true, you have a succesful product.

If however judging by the debates from various websites around the world concerning speculation about our own products and what our gasflowed head will or will not do. Bearing in mind we make no specific claims to avoid unqualified speculation. If this speculation is anything to go by, the buying public are very cynical. Probably more cynical than I am. Roland, good luck, I hope you have got your sums right because the buying public will bite you on the bum if you haven’t

I think it would be productive at this stage to agree to differ. Turner Engineering operate in a different area of the market than ACR as the overwhelming majority of our work is service exchange engines. Unfortunately I no longer have the time to play, and I have blown up a few engines in years gone by by playing around.

Trevort & Noel: Richard – I’ve been reading your posts on various threads with great interest. I finally clicked on the link to your website and I’ve found it very impressive and informative. With reference to the 300 Tdi, am I correct in concluding that your recommendation for improvement in torque would be a gas flowed cylinder head? What is your opinion on big intercoolers and increased fueling?


Originally posted by RolandACR:
Everyone must surely agree that Series vehicles need more power…

Nope. Everyone most certainly does not. Speaking as someone who is driving 20+ year old buses about to make a few quid at the moment I can testify that a 2.25 Land Rover does not need more power – the driver needs to be more aware and observant and understand the limitations of the vehicle. The aforementioned buses have a kerbweight a shade under 10 tonnes and have 10.45 litre 6 cylinder non-turbo diesel engines that develop 170bhp. I have no problems with their performance (either acceleration or braking) in heavy traffic, dual carriageway work, country roads etc and they are infinitely slower than a 2.25 Land Rover.

It all comes down to vehicle sympathy, at the end of the day if you want a Land Rover to compete with Trevor in his GTI then a 2.25 litre motor isn’t the one for you. Come to think of it, a Land Rover probably isn’t for you unless it’s a JE Engineering supercharged Range Rover or something like that.

You cannot change the laws of physics and no matter what you say, a 2.25 litre Land Rover engine, mucked about with to generate more power and revved beyond 5000 rpm on a regular basis cannot possibly last as long as an unmodified factory unit driven sensibly.

Your conversions are pretty impressive on paper, and I for one think it’s a good thing they are available for those who want them, regardless if I think they are a sensible move or not. Sticking to hard facts is a good move in my book, as has been said 100,000 miles isn’t particularly impressive when standard engines can reach 3 times that or more.

Turner: Trev, Yes, performance of both the 200 & 300TDI engine can be improved by simple but effective porting work to the cylinder head. All previous evolutions of Land Rover 4 cylinder engines have responded well to this type of work without prejudicing life expectancy. To this end if a customer specified a gasflowed head on any of our exchange engines, we would offer the usual 12 months unlimited mileage warranty and expect the normal life expectancy. However a customer proposing to modify pump/ boost turbo / intercooler etc would be another matter, as it would be with Land Rover.

Gasflowing the cylinder head is a much more technically correct way of increasing efficiency. It is possible, if you have seen plenty of Land Rover cylinder heads, to see variations in standards of gasflow of new heads. Some evolutions of Land Rover cylinder head are better ported by the manufacturer, this variation clearly does not affect life expectancy, merely efficiency. However due to the expense of removing and refitting a cylinder head on what is effectively a perfectly serviceable engine, I would only really recommend head improvements where the engine is coming apart anyway.

The problem is that because it is so easy to tamper with the injection pump and turbo boost pressure and get an instant result and gratification, this tends to be the preferred option. There appears to be no real understanding of the implications which have been discussed on various forums before.

If you were to consult the professional end of the market Ie piston manufacturers/ qualified engineers associated with examining engines and components that fail for various reasons, none of them are in favour of this type of modification and will usually quote examples of Volvo’s, Mercedes Benz etc where owners have damaged engines as a result of non standard settings on turbo’s and/or fuel injection equipment. Indeed we have seen quite a few exchange engines ourselves damaged in this way. In all cases the owners decided to return to original settings.

The practice of interfering with electronics, boost pressure, fuelling etc is becoming a major problem to motor manufacturers and now involves the truck market. If the practice of carrying out this type of modification was completely safe, why do motor manufacturers invalidate warranty as a result of this.

ACR: Richard, Several of the earliest 2.25 Power Plus engines we built have now covered miles close to 100,000 miles. As we expect, these engines are still producing the power and still use no oil between services. We expect these engines to continue performing reliabily for the next 100,000 miles.
The failure of military engines is interesting. We have also stripped many of these engines and find that major failures are almost exclusive to rebuilt engines you know the ones painted in horrible green paint. It is very rare to see a failure of the bottom end of an original Rover built engine. Closer examination of these failed engines shows that failures are almost exclusively due to assembly or other errors during the rebuilding process and not due to high RPM induced fatigue.

Noel, Here is a good example where the Power Plus system really comes in to its own. I know we have discussed high RPM and rev limits etc and I will admit that personally the pleasure I get from running my Series IIA is from having a 33 year old vehicle which will out run modern traffic. But anyway consider the following scenario
Series IIA/ III 109″ Station Wagon 2.25 pertol standard out put 120Ib.ft/68BHP its a good one!
You decide to take the family on a caravan holiday. So you load the vehicle and attach your caravan, so you have a 109 Station Wagon which weighs 2100kgs. say 450kgs for including the family of load within the vehicle and a caravan which weighs 1250kgs total 3800kgs. and you decide to head to Scotland. On the motorway. Those who have travelled with such an outfit will know the pain and embarrasement that results from having just 17.8BHP per ton yet it is all legal and Land Rover give their blessing for a train weight of 6760kgs so were not beyond limits. If you have travelled up the M6 North then you will know Shap Fell, 7 miles of up hill gradient that by the time you have reached half way you may be looking for the low ratios with lorries thundering past. Imagine the improvement an extra 30ft 16 of torque and 45BHP will make to the comfort and safety of your family all without as already explained spoiling long term reliabilty. You can add this to 2.25 by fitting ACR’s Power Plus system ie. camshaft, SU carburettor kit and gas flowed cylinder heads on to the existing engine and as many have found it brings whole transformation of the vehicle capabilities.

Turner: Roland, We are getting somewhere now. But you still haven’t answered the question – is it safe for Jo Bloggs to run any 30 yr old high mileage 2.25 petrol engine to in excess of 5000 revs on a regular basis without affecting the life expectancy. I am not talking about one of your rebuilt engines 2.25 – 2.8 or otherwise.

Whilst I agree that most military green engines are not particularly well built, the type of piston failures I mentioned were not connected with build quality and entirely due to operating conditions Ie stress related. Even the military cannot incorrectly assemble a piston onto a conrod. Providing the bore is the correct size, that’s it. You can’t blame poor assembly for piston breakage (not seizure as a result of overheating, detonation or other). So are you suggesting that a high percentage of military engines are not suitable for high performance tuning because they are badly built. I merely pointed out specific type of failure connected with operating conditions.

Now lets start thinking about original Rover built engines. Engines which have been rebuilt on a DIY basis, or by slightly less than diligent profesional mechanic who has incorrectly assembled the connecting rod bolts in a way that drags a burr down into the counter bore of the conrod. This within the normal working parameters will generally work without too much problem. However under high stress, high rpm the bolt has the potential to settle further into the counter bore, the cap works loose and the big end fails. I have seen this type of failure in a number of petrol engines over the past 20 years or so, not necessarily military. Are we to conclude that revving an engine that has been rebuilt by someone other than the military cannot fail if regularly revved in excess of 5000rpm? Or do we have to accept the possibility that some engines have the potential to fail as a result of inbuilt defect.

How do Land Rover owners determine whether their engine is suitable to be revved beyond 5000rpm which you appear to advocate as safe, or do we conclude that it is only really a good idea on a properly rebuilt engine. This would be somewhat of a shift from your original argument.

Roland, I fully accept that the risk is low, but nevertheless a tangible risk does exist. The law of physics dictates, the higher the rpm, the higher the risk.

Crashbox: Very interesting posting by Roland, the fact that the effective compression ratio of a petrol engine varies greatly according to load is not widely understood but is important. Valve timing also affects the true CR of an engine, since at low engine speeds at least, the actual volume of compressible mixture (or air on a diesel) you can achieve depends on how far up the cylinder the piston is when the inlet valve closes. Thus a petrol engine with “hot” cam timing and a high compression head will have poor torque at low revs but will go like the clappers at the speeds the engine is optimised for. Tuning mods on a LR engine have to be relatively mild, since you cannot afford to lose low speed flexibility. I would bet that a lot of the power increase on the ACR kit comes from the SU carb and the fact that the charge density is higher as the inlet manifold is not getting all the heat input from the exhaust that a standard set up does. This lower induction temp also allows a higher CR without detonation on the same octane fuel.



Originally posted by crashbox:
Thus a petrol engine with “hot” cam timing and a high compression head will have poor torque at low revs but will go like the clappers at the speeds the engine is optimised for.

Crashbox You sound like you know what you are talking about. Would you like to venture an opinion as to what happens to an engine’s efficiency, pertaining to hydro carbon emissions and idling characteristics.

Crashbox: Engine efficiency in a petrol engine will be at it’s highest if you can completely burn the fuel at a lean A/F ratio, and using the highest C.R. for a given octane fuel. Hydrocarbon emissions and idling quality are inter-related. A “hot” tuned engine will most likely have a lot of valve overlap. Good for “scavenging” at high revs, but not good for emissions or fuel economy. If the inlet valve opens much before TDC, exhaust gas can escape into the inlet port and contaminate the fresh mixture. This gives rough idling and you have to set the mixture extra-rich in order to be able to burn it. The overlap allows unburnt mixture to escape straight out of the exhaust port, where it partially burns with the exhaust gas. Fuel is wasted without producing power and HC emissions go through the roof. On a diesel overlap does not pollute as you are only dealing with air, not fuel mixture, but the timing still needs to be optimised for the speed range of the engine.

Turner: Crashbox – Excellent could not have put it better myself.

There is however somewhat more to this than meets the eye. It is not just a question of convincing the MOT tester or worrying about costs of fuel consumption. When an engine runs rich, unburnt fuel causes various internal effects such as abnormal valve guide wear, abnormal piston ring wear, and as a result of the degredation of engine oil, camshaft/follower wear. This will ultimately reduce life expectancy and increase operating costs.

I think we can now conclude that this “hot” engine format when run at it’s optimum speed Ie high rpm will increase mechanical stress and fuel consumption. Low operating speeds outside of the optimum speed will be inefficient, sluggish and costly in fuel consumption and resulting excessive engine wear. Bearing in mind the life expectancy of a 2.25 petrol under favourable operating conditions is 3 to 400.000+ miles. Ie 30 to 40 years at average 10.000 miles annually.

Next question:-
We want to achieve maximum miles per gallon, improve driveability (torque), especially at low rpm, reduce the speed at which max. BHP is achieved, reduce HC emissions, run on premium unleaded and improve life expectancy. How can this be best achieved without increasing compression ratio.

PS – good to see people participating!



Originally posted by R Turner:
Next question:-
We want to achieve maximum miles per gallon, improve driveability (torque), especially at low rpm, reduce the speed at which max. BHP is achieved, reduce HC emissions, run on premium unleaded and improve life expectancy. How can this be best achieved without increasing compression ratio.
Richard Turner

PS – good to see people participating!

Richard, I think I know where this is leading, but here goes:-

If you specifically exclude increasing the C.R. (although I would for the thermal efficiency gain), you are basically left with improving the volumetric efficiency.
To run on 95 RON U/L fuel you need to fit suitable valve seats, and possibly guides.
While doing this you can get the engine to breathe better by employing three angle valve seats & tidying up obstructions in the ports, which you just happen to do on your “performance” heads.
If you want economy & low speed torque the standard camshaft with only 29/30* overlap must stay. Looking at the 3 brg 2 1/4 petrol valve timing, possibly advancing the cam by a FEW degrees might give a little more torque as the inlet valve will close earlier. You may also gain in reduced pumping losses by the opening of the exhaust valve a little earlier too, as the LR petrol exhaust valve opens very late even for a “slogging” engine. (I assume the reason for this was to give the 24* of exhaust lag to try and maintain the torque at higher speeds). This could improve economy. Take it too far though and you contaminate the fuel mixture with early Inlet opening. So far we’ve got the engine to breathe a bit better at low speeds. Not very sexy maybe, but think about the speed range a typical series Land Rover engine may be used over. It idles at ~500 RPM, with 7.50 tyres and O/D 60 MPH is 2850 RPM. A sensible maximum road speed in a leaf-sprung model can’t be over 75 MPH, and this eqates to 3,500 RPM in O/D top. So really it’s pointless in having the peak power much above this speed if economy and long life is your priority. Remember when series 2 Land Rovers first came out they didn’t have overdrives so at 70 MPH the engine would be running at 4,250 RPM (on 7.50’s). The engine needed to peak at this RPM in order to provide the power to overcome the aerodynamic drag. If you raise the gearing (5 speed box/overdrive) then you need more torque but at a lower speed to take advantage of it. From my point of view you want something which will pull from idle, plenty of torque – peaking at about 2,000 RPM, and a power peak of about 3,500. The big spin-off of keeping engine speeds low is that mechanical stress is reduced as it increases with the square of speed, so the components in an engine running at 5,200 RPM are under 2.2 times the stress of the engine peaking at 3,500.

Question for you Richard:- Why don’t you favour increasing the C.R.?

ACR: Richard As stated on 3/1/02 we set the red line at 5200RPM on the 2.25 Power Plus engines. Obviously we also supply equipment which is retro fitted to older engines as well and customers often ask what happens to reliability? Our advice is simple, if the engine is running well, ie. consuming little oil, a minimum of ring blow by and running smoothly and quietly then the fitment of Power Plus components is recommended, if there is any doubt then spend the money getting the engine up to spec. first, by that we do not mean re-ringing, replacing bearings in situ or other patch up jobs! Experience has shown that the use of Power Plus componentson good used units has not resulted in wrecked engines just happy customers.
As for advice on RPM limits for old units who can guess? However if I was fitting parts to a used engine that I knew well, then with no hesitation I would set the limit at 5200RPM.

Turner: Thank you. We are agreed then that it is not safe to rev just any Land Rover engine to in excess of 5000rpm. The most likely reason that there is so little trouble with performance tuning 2.25 petrols is that most owners have the sense not to drive like this as a result of the appalling fuel economy and mechanical risk that goes with this type of driving.

Crashbox: Richard, firstly if I’ve appeared to belittle the amount of modification that goes into your gasflowed heads then I apologise. I’ve seen one in progress so I know a lot of work goes into them.
From a technical point of view, you are optimising the flow capability of the port, although it is a complex subject with many variables. Ob,structions like the valve guides and casting nibs etc reduce the cross sectional area of the port. No doubt you have found it beneficial to open the port a little where it’s flow is not optimum. Obstructions cause turbulence in the gas flow, which you do not want in the exhaust as it hinders the escape of waste gas out of the cylinder. If you can get the cylinder to exhaust freely you reduce pumping losses and facilitate drawing in the fresh charge by creating a depression. A free flowing induction port gives a high volumetric efficiency even with short cam timing, so there’s more charge to compress in the cylinder. Provided you can maintain the fuel droplets in suspension in the induction tract, the engine should run smoothly & deliver good economy.
One area where I’d disagree with you up to a point is the issue of C.R.’s, although I can understand your commercial reasoning of selling a “hassle-free” product. I have a 2 1/4 petrol which was unleaded and skimmed by yourselves, but was not gasflowed. With +.020 pistons fitted I reckon the C.R. to be approximately 8.8:1 It has performed very satisfactorily with no problems with detonation or running on at all. Actual power output is not that noticeably higher, but it pulled strongly at low speed & with improved fuel economy – what I set out to attain. I believe that the reduced clearance volume of the skimmed head improves V.E. as well as giving higher compression pressures anyway.That head will be transferred to my series 2 and one future modification will be to weld shut the open top of the exhaust hotspot in order to reduce intake temperatures & increase charge density. This should help offset the risk of detonation with the higher C.R. As I like tinkering about the trial and error setting necessary to get the best out of a non standard set up is no bother, the book figures are only a starting point.

Turner: Crashbox, I didn’t know you own one of our cylinder heads. It wasn’t ordered under the name of crashbox!

I agree and you have convinced me. Maybe we are over cautious and we should be more actively promoting this type of cylinder head. It is actually listed on our website and I have sold a few over the years to those who have requested this type of product for competition or their own fun. In fact one overseas customer buys this spec 5 at a time to use on engines with standard carburation and their own modified camshaft and big bore exhaust system. They are extremely satisfied with the overall performance.

As to cost, we do not charge extra for increasing compression ratio, the skimming is an automatic process on the CNC and only requires an edit to the program. Afterall the hard work is in the porting. We usually manufacture this type of head to order only.

As to your own cylinder head experiences, as far as compression ratio is concerned, this is consistant with the experience of an army lightweight entered in the Mintex Rally some years ago. The first year the LR was raced using a high compression head, probably around 9:1CR without gasflowing, standard Zenith carb and standard ignition. The second year this vehicle was entered we were asked to supply a head that was gasflowed to our usual specification and skimmed to around 9:1CR, again standard setup. This seriously transformed the vehicle, with the unexpected bonus of saving fuel on the special stages under race conditions.


Originally posted by John Wright:
I understand you sticking to standard carburettors to remove the setup problems but do you not agree that the standard Zenith can be gainfully replaced by an SU or a twin choke PROVIDED that it is properly calibrated.

John, I would always advise original equipment Ie Zenith. The Zenith is cheap and simple to work with and a short job to replace. Most garages can rectify setup problems on original equipment with minimum fuss and cost. Alternatively try Clive Greenways at Greenways Engineering, he is a carburettor specialist and should be able to offer advice/carburettors to meet most requirements

And off course Crashbox is pretty clued up as well as we have found in this thread. My speciality is internals and machining, therefore I am better placed to advise the effects that various types of ancillary components have on internal parts rather than specifics concerning ancillary setups and tuning.



Originally posted by R Turner:
[QB]Next question:-
We want to achieve maximum miles per gallon, improve driveability (torque), especially at low rpm, reduce the speed at which max. BHP is achieved, reduce HC emissions, run on premium unleaded and improve life expectancy. How can this be best achieved without increasing compression ratio.QB]

Crashbox, If we are to meet the above criteria, this rules out hot cams and non standard carburettors and leaves us with one option which as you rightly say – improve efficiency. How do we do this? We thoroughly gasflow the exhaust and inlet ports on the cylinder head. This is time consuming and means considerable time spent grinding material out of the ports. Most people choose the compression ratio route rather than spend the time required to gasflow the head properly.

Q – What does all the gasflowing achieve on a 2.25 petrol.
A – 120ft lbs of torque at 2750rpm. 70bhp at 3300rpm.
This test was conducted regularly on 2.25 petrol engines on a calibrated Heenan & Froud G3 Dynomometer. The engines tested were newly built and not run in and therefore still not realising their optimum potential and may well have produced more impressive sounding figures had we looked for power higher up the rev range. All ancillaries fitted were standard, standard camshaft, premium unleaded fuel.

OK the above does not sound like an improvement does it, until you start talking to customers and driving the things.

Example 1
S111 LR SWB high ratio diffs, standard carb (Zenith) & ignition, 8:1 gasflowed head. Prior to conversion usual cruising speed 50mph. After conversion driver reported significant improvement in driveability. Described as, using the same throttle input to achieve 50mph previously, now produced 70mph. He now cruises at 55mph at a significantly lighter throttle opening. Better hill climbing and towing Ie pulls higher gears at lower revs and as a bonus has improved fuel economy.

Example 2
LWB Safari LR, 8:1 gasflowed head, ACR SU carb & manifolding. Regularly outperforms S2a SWB with the full ACR setup IE carb, manifold, camshaft, 9:1 head. Is however just within MOT HC limits.

Example 3
Jim Allen, writer for LRO early 90’s. Feature LRO May 1991. Supplied 2.25 long engine with gasflowed head, 2.5 petrol camshaft. Fitted externally with a 4 into 1 tubular exhaust, a custom built low restriction exhaust system (oversize pipes and freeflow muffler) a Weber 28-32DGV twin choke carb on a Pierce manifold and a late style Lucas 45D distributor with luminition electronic ignition and K&N airfilter. How did it perform. “in my case all the modifications added up to a rip snorting 2.25, hill climbing on the highways is light years better than before. Hills that once required 3rd or lower can now be pulled at top gear at close to the speed limit. Top speed has increased to well past 80mph because the rpm range and power curve is extended significantly.” Jim’s opinion was “as far as how my engine turned out I can make a subjective evaluation, since the twin choke carb, exhaust modifications and ignition were installed on the previous engine which also had a fairly fresh valve job. The increase in power must be due to the modified cylinder head and 2.5 camshaft and a good rebuild. The Turner high performance head is ported with emphasis on the exhaust side. Cylinder head modification is a situation where a little work done in the right places reaps more benefits than a lot of work in the wrong place”.

Example 4
Customer booked in a 110 LR to be converted from a turbo diesel engine to a 2.5 petrol. The engine was built to our normal standard, 8:1CR gasflowed head, new carb & distributor, produced 83bhp at 3300rpm and 135ft lbs of torque at 2750rpm. This vehicle was road tested and easily reached an indicated 90mph and would still pull 80mph on slight inclines.

Example 5
Ex para trooper owns LWB S111, specifies 5mb 2.25 petrol to be fitted. 2.5 camshaft, Zenith carb, gasflowed 8:1CR head, electronic ignition. Reported speeds in excess of 80mph achievable.

All this without having to resort to compression ratio changes. Why don’t we favour increasing the compression ratio.

1. How do you predict the exact compression ratio. Not too difficult to work out on a new engine, but as bore sizes increase with rebuild, compression ratio increases.

2. At Turner Engineering we mass produce cylinder heads, which can be sold anywhere in the world. 8:1 has given tremendous results in it’s gasflowed format over the past 17 years. Fuel quality varies around the world. How does one determine advice to give to a customer in Bangladesh for example as far as timing is concerned.

3. Insurance companies are not keen on compression ratio changes.

4. Most cylinder heads will ultimately be supplied to customers with engines, carbs, ignition systems, radiators etc which have been in service for some years and may not be as efficient as they should be. This would give the potential for problems with setting up the engine. Increased heat output via the cooling system that is past it’s best then has the potential to become a problem.

5. Due to the potential for detonation with higher compression ratio’s and that an 8:1 gasflowed head will happily run at 6 degrees BTDC without problems, we have to be aware of the potential where owners can make mistakes in overly retarding or advancing the ignition. Not to mention faulty distributors and or carburettors. We do not want complaints concerning failed head gaskets, melted pistons or other types of engine failure associated with abnormal combustion temperatures.

6. There are geometric problems. When skimming a large amount of the cylinder head, the push rods can end up too long and adjustment on the tappets runs out, requiring shims. Head bolts can bottom out, reducing torque to the head resulting in head gasket failure. Head may ‘jack up’ on the waterpump. You may not be able to skim the head again if it requires service in the future.

The fact is that a 8:1CR head format for all intents and purposes under reasonable operating conditions is 100% reliable, gives outstanding performance in a gasflowed format and generates virtually no queries. Do we want to take the risk of increasing complaints by supplying a 9:1CR head, other than for competition use, or to clients who can properly set up an engine using new ancillaries and can carry out the correct adjustments to tune in a non standard carburettor should they choose that route.

Clearly there is a market for high compression heads and bolt on ancillaries. Logic however dictates this format is more suited to competition use or where life expectancy and/or fuel economy is of secondary importance.

Our philosophy has been to offer the day to day motorist improved performance and economy at little more than the cost of a standard lead free cylinder head. But this gasflowed cylinder head supplied in a 9:1CR format and used with non standard ancillaries will outperform anything on the market and has performed extremely well in competition. This is not particularly well known due to the fact that we have not particularly tried to market this type of product due to the time required in explaining the in’s and out’s to potential customers. Our work load these days is geared towards the later diesel engines.

Next question:
Care to venture an opinion as to why the 8:1CR gasflowed head performs so well. What is actually going on from a technical point of view.

Crasbox: Don’t bother with gear timing on a petrol, I’ve never heard of a LR engine chain breaking like diesel belts do, there’s less load on a petrol drive (no injector pump).

Camshafts:- Engines with serial nos. beginning 361 have the petrol cam. Timing:- IVO 6* BTDC, IVC 52* ABDC, EVO 34* BBDC, EVC 24* ATDC. (Part no 274709 stamped on it).
991 and 366 engines have the diesel type cam, part no 274711. Timing:- IVO 16* BTDC, IVC 42* ABDC, EVO 51* BBDC, EVC 13* ATDC.

The main difference is the diesel type cam has slightly more lift and opens for six degrees longer. Average diesel cylinder pressures are lower so you tend to open the exhaust valve slightly earlier to give the gas time to escape. That does not necessarily mean it will benefit the petrol’s economy to have the same timing as you may waste useful cyl pressure. Comparing the 2 1/4 petrol and diesel/2.5 cams, the 2 1/4 petrol inlet valve closes 10 degrees later (52*/42*) and the exhaust opens 17 degrees later (34*/51*) – quite a big difference.

If you advanced the timing on a standard petrol cam by 4*, using the adjustable keyways you would get:- IVO 10* BTDC, IVC 48* ABDC, EVO 38* BBDC, EVC 20* ATDC. E.P. would be 99* BTDC using a DTI guage for timing.

The inlet valve still opens late so smooth idle will not be affected, it closes 4* earlier so low speed torque should be marginally improved, the exhaust opens slightly earlier so you should get less pumping loss but without losing useful pressure. The exhaust closing earlier will have the least effect, but overall the torque output will probably be higher, but peak slightly lower down the rev range than before, everything else being left alone. As a result, you will likely lose a couple of BHP, but get it back again as a result of the higher compression ratio.

All this is theoretical mind you, but I think the overall effect will be approx the same BHP, possibly a few hundred RPM lower down but more torque for towing or maximising the use of the overdrive.

I intend to time my 2 1/4 petrol exactly as above to see how it goes, but I’ll have to wait to get the series 2 back on the road before I know what it turns out like.
Economy & torque for O/D use is my aim, top speed is unimportant to me.

Turner: Crashbox is correct, save your money for hardware that will improve performance. Gear kits generate mechanical noise (vibration) and do not have 100% reliability record. Both ACR and APB Trading offer an SU conversion. The APB kit had the rolling road work done by Clive of Greenways Engineering.

Crashbox, If the 2.25 petrol camshaft gives slightly better performance at higher rpm would this not be the best camshaft to use if you are intending to increase the compression ratio. Higher compression engines perform better at higher speeds? (I am talking under 4000 revs).

Conversely if the diesel cam 274711, ETC 5475 or ETC 7128, which as far as I am aware are all similar or the same give better performance at lower revs and run out of steam higher up would be better with a low compression or 8:1CR head.

As to advancing the valve timing by 4*, with the 2.25 petrol camshaft would this ultimately be better allround or would one be better of using the diesel spec camshaft or the diesel spec camshaft advanced by 4*?

There is a camshaft gear (o/e item) used in the 2.5 petrol that alters the valve timing slightly in conjunction with ETC 7128 camshaft. Which way it alters the timing I have no books available at home to look up. This if it were somewhere close to correct would be the easiest way to set the timing without the use of special tools. This gear only has one slot as opposed to the old type gear, which is multi splined. A slight problem however arises for people with late 2.25 5mb engines, built with the latest timing gear, it only has one spline. So incremental adjustments are not possible. Should this 2.5 petrol gear be in the ball park, this type of modification is effectively endorsed by Land Rover and could be fitted by any reasonably mechanically competent person.

If we use this debate to establish a build spec (not including ancillaries) to give the best possible all round driveability in the 2500 to 3500 rev range, utilising the best o/e spec components available, without compromising life expectancy, we have various options. Two choices of o/e camshaft, things we can do with the base line setting of them and compression ratio changes.

We have four options open to us on compression ratio.
1. Increase the cylinder bore size
2. Skim the cylinder head
3. Skim the cylinder block – gasket approx 1mm/040″ thick. Pistons typically .25 to .50mm or .010″ to .015″ below the deck. The piston can come up quite a way before there is any risk of contact with the head casting.
4. A combination of all three above combined with gasflowing the cylinder head to improve volumetric efficiency.

Over to you.

Crashbox (Roger ?): Richard, I don’t see any reason to confine the use of a higher C.R. to engines optimised at the upper rev range. The way I look at it, if you can increase the BMEP then you gain at all speeds, and part throttle economy is improved.
The 2 1/4 petrol timing looks “lopsided” to me – VERY mild IVO/EVO timings, yet IVC/EVC optimised for midrange performance. I get the impression from this that the cam timing was retarded during development to hold up the torque at higher speeds. 24* ex.lag is a lot on an engine with only 6* inlet lead, IMHO. I doubt if it gives the best economy either at higher speeds as that exhaust valve opens so late as a result that negative work MUST be done by the piston on the upstroke to push out the waste gas.
I certainly wouldn’t advance a diesel cam at all, let alone 4*, the inlet would close extremely early & exhaust could well waste useful cyl pressure by opening at 55* The inlet would open early too, would it idle OK?
In reality, you’d need to test on the dyno at different engine speeds with a fuel flowmeter to see which set up was most economical, I’m only really guessing.
You quote optimising the engine in the 25-3500 RPM range. To my mind that is too high. I’d say the typical LR driver changes up by 2500 going through the gears, only in top at high road speeds are the engine revs going to reach 3500.
Regarding the methods used to improve performance:-
1) I wouldn’t bore out the block. +.040″ only gives you 52cc extra and renders the block scrap when the bores wear. If you want volume then surely a 2.5 is the better choice? The pistons are also heavier and out of balance forces greater.
2)Skimming the head within reason would seem to be the best way provided you consider deck thickness & rocker adjustment. It is a bolt-on conversion rather than an engine out job then.
3)Decking the block much would surely give you extra work chamfering all the cyl head threads in the top of the block. You would gain more increase in C.R. per thou removed though than off the head if that was an issue.
4)Gasflowing and C.R. increases will both improve the VE, because in the latter the unswept volume of the cylinder is reduced. To produce a given torque you need a certain BMEP. The higher the static C.R. determined by the clearance volume and inlet valve closing point, then the less fuel you need to burn to achieve that cylinder pressure. This gives you the potential to produce more torque with a lower S.F.C. That’s my thinking anyway.

Turner: Roger, Your camshaft could be either, clearly there are slight differences but most drivers really would not be able to tell the difference.

As far as LPG is concerned. I am not an expert but I understand that due to the different combustion characteristics this type of conversion can benefit from a slightly higher compression. However due to the higher operating temperatures involved with LPG, valve, valve seat insert and guide wear is higher, despite converting to unleaded/LPG style head. Due to the general loss of power associated with LPG, a gasflowed head compensates and possibly a 8.5:1CR as you suggest would be sensible.

I recently supplied a gasflowed 9:1CR head to a person who works in the performance industry and thoroughly researched all sources for performance equipment including taking advice from an American company with experience in LPG reaching back to the 60’s. The advice was do not exceed 9:1CR. Once fitted he was extremely pleased with the outcome.

Changing the camshaft is a major undertaking and should really only be considered if the current camshaft is worn or damaged. There isn’t sufficient benefit to warrant changing from petrol 2.25 to the later 2.5 petrol/diesel camshaft or vica verca. The problems with non standard (hot) camshafts are documented earlier in this thread.

Judging by the comments from people enquiring I truly believe that many people are put off improving their engines by believing that it is a major undertaking or that they have to spend a serious amount of money on aftermarket equipment.

We have advocated for years that it is not necessary to change anything other than the head to gain a noticeable improvement in performance and economy. Making this the most cost effective conversion for the day to day motorist.

However due to the superior gasflowing on our cylinder heads (we retain samples of others for comparison) the option exists to change ancillaries to non standard such as ACR SU carb and manifolding setup, APB Tradings SU setup, or a similar set up to Jim Allen, and get better performance taking into account crashbox’s comments as to emissions and other problems associated with this type of external component conversions.

Turner again: Crashbox, Common sense and practicality dictates that anywhere between 8 & 9:1CR + gasflowing all ports using either petrol or diesel spec camshafts will work fine for Jo Bloggs without incurring additional costs and aggravation changing camshaft or bolt on goodies. I agree on your comments as to 2500 to 3500 rpm being too high on the rev range but it is important that an engine pulls strongly at these kind of speeds for high speed motoring with OD. Fortunately this specification also gives good low speed pulling.

For example:
One of our part time workers has a S111 SWB which was fitted with this a gasflowed 8:1CR head. Everything else standard inc. remanufactured Zenith carb, engine has covered in excess 200.000 miles and pulls strongly from no revs at all in all gears. Literally a fast idle. Once you reach 50mph you have to start consciously to back of the throttle as the next thing is that you are doing 70mph. At the age of the engine it will have a petrol spec camshaft. This I believe is the kind of pulling power most people are looking for and can be achieved at minimal cost and with no risk to long term life expectancy and reliability.

As to your point 1, 060 pistons are available and also liners for the 2.25 petrol.

Point 2 – agree

Point 3 – removing a small amount from the deck of the block causes no problem.

Point 4 – agree

As to the timing figures for a 2.5 petrol/diesel camshaft ETC 7128.
inlet peak 108* ATDC
exhaust peak 104*BTDC
At a glance, because I have not spent much time on this, the 2.5 camwheel appears to rotate the timing and retard everything by 5*. Is this good or bad.

I am rapidly conming to the conclusion that this debate vindicates our policy of keeping engine build specs extremely simple and boringly standard. There would be nothing more embarrasing than having fouled up or having made a mistake or altered an engine operating /emission characteristics for the worse. If this situation should arise it does your credibility in the market no good at all. So we stick to our policy of gasflowing only as we have always done with a product that now has 17 years of proven product reliability behind it.

There does appear to be some advantages to a higher compression. This option has been available alongside our gasflowed head for those who requested it over the years. However one has to remain cautious in offering this type of product to markets with low fuel grades, for example North America where fuel is available at 90 octane and less, and where you regularly read comments on problems with detonation associated with high compression.

Hopefully this thread has given people an understanding that increasing performance outside of the standard specifications is an extremely complex subject and potentially fraught with problems to the unwary.

ACR: Richard / Crashbox, Just to clear up a few points regarding ACR’s Stage 2 head and Power Plus camshaft
The Stage 2 head is much more than just a skim we rework both the ports and combustions chambers. We do this firstly with boring cutters from both the port side and valve side of the head on our CNC machining centre followed by hand work to blend in the new maching with the existing ports. The head is then assembled with new valves, guides and springs along with the correct dimensioned valve seat inserts. The result is an extra 30% increase in air flow through the intake port as tested on S.F. flow bench on an independant university facility (thanks to Andrew Watson HND project). In real terms this adds 15BHP when fited to an otherwise standard engine. This is the very first modification to perform on the 2.25 engine it is excellent when used with LPG and customer surveys record MPG improvements.
Regarding camshafts we have found it very difficult to get good results with the ETC7128 diesel camshaft on 2.25 petrols. Extensive dyno testing has shown that retarding the camshaft some 8 degrees followed by opening up valve clearances to some 0.020″ on the exhaust was the only way to acheive an improvement over the earlier petrol camshaft, we put this down to the fact that the cam has very long opening ramps and the factory timing settings result in early opening of the exhaust this can be confirmed by the incidence of cracking on exhaust manifolds and burnt out down pipes on early 90/110 2.25 engines with this cam fitted.
That is why we developed the Power Plus camshaft basically the Power Plus camshaft has similar duration and overlap to the standard camshaft ( the lobe centre angle also remains at 106 degrees). What we have done is optimised the valve lift rate and increased maximum lift slightly so the cylinders have a better chance to fill, hence increased torque output with this cam. It is a brand new cam not a reprofile so the base circle remains standard and keeps the stress low on the followers. The optimum cam timing with this cam is with “split overlap” ie. inlet and exhaust open by the same amount when the engine is at TDC on overlap. The 6 way chain wheel can be used to acheive this condition.
I hope this clears up any speculation that the ACR Power Plus camshaft is a hot race cam!
A note for those who wish to use the standard intake manifold with its single down draught carb. eg for soem Rover Club competitions. We have built quite a few of these set-ups and offer the following advice – separate the intake from the exhaust by maching the exhaust hot spot face and fit a plate to seal the hole , also dump the Zenith and use a Weber – reported to have better air flow and jets are available should you need to recalibrate.
Finally Richard why do you fit non standard dimensioned exhaust valve seats? We have a stack of your old heads here and we cannot remanufacture them.

Turner: Roland, Excuse me, you claim to be the independent market leader and you claim you can’t remanufacture our cylinder heads?! What do you do with all the other heads you get in exchange or buy in that have been reworked elsewhere.

There is no such thing as a correct dimension for a valve seat insert used in remanufacture and certainly no obligation to use o/e equipment. We have used several types over the years. Our current supplier has three options, two alloys and one sintered. The sintered are the cheapest. I avoid Land Rover inserts due to their sintered construction which has a tendency to shrink if overheated and prefer to use inserts that are more reliable under abnormal or extreme operating conditions. With the range of aftermarket inserts, valve seat removing and inserting equipment available from various sources, stating that you can’t rework our heads is complete nonsense. Or are you saying you haven’t got the equipment or experience to deal with anything other than Land Rover inserts or a head that has never been reworked before. Normally most seats merely need recutting with a three angled seat cutter.

At Turner Engineering we have remanufactured some 8000+ cylinder heads petrol & diesel over 20+ years, many which had been reworked previously in all kinds of ways with military heads remanufactured by subcontractors using cast iron seats to non standard seats from various local jobbing shops. We have no problems, it is extremely rare that we encounter a cylinder head that can’t be remanufactured irrespective of previous reworking. If you care to give me the serial numbers of the heads you claim you own and provided the castings are serviceable I would be happy to buy them from you or alternatively rework for you at a favourable rate. As to the pro’s and con’s of your own product it would be highly unprofessional to comment in detail as to their actual technical specification.

We appear to have lost track of an interesting theoretical debate. This thread, has served it’s purpose to advise interested parties the pro’s and con’s involved with tuning Land Rover engines in order that they can make a considered descision as to which product(s) to buy if any from various sources available.

Gavin: noticed that Richard mentioned the deck height and it’s effect on compression. This is very true but also has another more significant effect, it reduces the volume of the quench area. This is an area where complete combustion is difficult as the flame front can not travel into it at TDC, combustion therefore takes place as the piston travels down the bore (wasted energy and fuel). Reduction in this area reduces this wasted fuel.
The effect of compression ratio increase has the effect of more complete and efficient combustion from a given fuel (octane permitting). This happens at all engine speeds, so therefore for any given air/fuel mixture given more complete combustion will take place. Many peoples concerns seem to be that of good MPG compression increase should help this not reduce it.
The main thing that has to be remembered is that an engine should never be viewed as a single component and part of a chain. All parts of the drivetrain, vehicle weight, aerodynamics and tyre size have to be cosidered. In standard form a series LandRover is not a good example of complete vehicle engineering. The gearing of it must be one of the single most limiting factors in it’s abilities as without a overdrive at normal road speeds the engine is past it’s peak and is unable to maintain this speed on hills.

Turner: Gavin, I thought I had finished with this thread. Excellent point. This is why I mentioned this particular aspect to see whether anyone picked up on the technical aspects of this syndrome. I have been of the opinion that this may help turbulence by more violently displacing air/fuel mixture into the combustion chamber area but there are obviously other benefits.

John Wright / John Boy
V8 engines are not my speciality, however we have built a few over the years and developed several procedures to allow CNC machining of the block casting, cylinder heads and conrods. Due to demand for 4 cylinder engines we no longer supply V8 exchange engines, but continue to remanufacture heads and supply parts when requested to do so. There are specialist V8 companies that are extremely clued up on this subject. But for an economical repair/upgrade the following is a good place to start and counts for all types of V8.

The exhaust port is particularly restricted and there is considerable scope for gasflowing. Most V8 power losses occur as a result of wear to the camshaft, hydraulic lifters, pushrods, rockers and timing equipment. Pistons, crankshaft and shell bearings do not wear so rapidly and a good cost effective repair/upgrade consists of replacing the afore mentioned items to restore valve lift and gasflow the exhaust ports on the cylinder heads can restore the original performance and some

ACR: Richard, We do not remanufacture our heads with seat of spurious dimensions for the simple reason that we offer a premium product and we consider it important where possible to keep parts standard for ease of replacement worldwide. Whilst we do obviously offer our Power Plus performance system which is clearly a deviation from the standard specification the differences are clear and well documented for ease of servicing and spare pasrt back up.

Turner: Roland, I re iterate from my previous post.

There is no such thing as a correct dimension for a valve seat insert used in remanufacture and certainly no obligation to use o/e equipment. We have used several types over the years. Our current supplier has three options, two alloys and one sintered. The sintered are the cheapest. I avoid Land Rover inserts due to their sintered construction which has a tendency to shrink if overheated and prefer to use inserts that are more reliable under abnormal or extreme operating conditions.

As to the pro’s and con’s of your own product it would be highly unprofessional to comment in detail as to their actual technical specification This debate is over.

Iaian: I have to agree with the awestruck view that so many others have expressed. This could never have hapened in a magazine. as we are aware and have been told, magazines won’t print unfavourable, or even sceptical articles about their advertisers, and they all shy away from any detailed technical discussions as this can frighten off novice readres. (have they ever stopped to wonder if letters about “what’s the best landy for me, I’m 14 and I’ve got 2k to spend, I want to get bucket seats, a roll cage and white 8-spokes with 265/75 MTs! can you help?” in every issue will scare off the less novice readers?)

I used to live in Liverpool. I drove down from Edinburgh with 2 1/4 ptrol 109 filled to the brim with everything i owned. I checked it on a weighbridge out of intrest before i left, and it was just under 2600 kg. Driving up the M6 was hell. i was down to 30 mph in 2nd gear going up to shap. Even when the engine is built for torque at low revs, you can still squeeze out the most power with high revs. it may not be the best for the engine, or economic but when 40 tonne HGVs are shooting past with horns blairing, that’s not your main concern.
That was a very healthy engine that had previously been giving me a steady 25mpg.
While i was in liverpool i popped across to visit Rolad on a couple of occasions and fitted a stage 2 head, and the exhaust from the power plus kit.

When i returned from Liverpool the 109 had even more stuff in it and a trailer.
The mods to the engine may not have boosted the power by more than 20 bhp, but it made an enormous difference. 3.5 tonnes of rolling weight, and it never dropped below 40 mph on the M6 (the a701 is another story), and managed 50 most of the way. The engine was much happier at high revs, which meant less gear changes, and a much more pleasant drive.

As for compression ratio, LR made vehicles with low compression ratios for a very good reason – the engine was built in days when the fuel quality was much worse, and in some countries it still is. For the guys in Lesutho who are still feeding their landies on parrafin when the petrol runs out then a 7:1 Cr or less is nessecary. for most people in the world fuel is normally of a very high quality, and there is no reason not to increase the compression ratio as it offers a very simple and effective way to improve efficiency.
It’s childs play to work out how much you need to skim to give a cr of 9:1
the engine is 2286cc – each cylinder has a displacment of 571.5
1/7 is 81.643cc (combustion chamber for 8:1cr)
1/8 is 71.4375cc (combustion chamber for 9:1cr)
1/7 – 1/8 = 10.205cc to be skimmed.
bore is 8.88cm
area = 2*Pi*D = 55.79468553 cm2
10.205/55.8 = 0.183cm

The same engine in diesel form can cope with much higher crs than that, so durability should not be a question.

I’d now like to hear both (richard and roland) your opinions on OILs to be used in this engine – how do i ensure i get to 400,000?
Should i splash out on castrol magnatec for basic engines, or stick to halfords cheapy stuff?
again this is something that has improved a lot in quality since ’58, so the LR way might no longer be the best.

With any luck you might agree on this one…

Iaian again: I find this information is good as it is addressing low speed torque and low-end horse power. Most performance information available in this country (Canada) seems to be strictly for the high horse power Hot Rodder. High power, high speed and the higher the rpm the better. A change to a cam usually means it will idle like an antique tractor and power doesn’t really develop till the tires are smoking. Horse power is talked about in hundreds.

Something similar in both cases is the movement of air both into and out of the cylinders. As said before, the easier it goes in and comes out the better no matter it be a 140 cubic inch Land Rover at 80 hp or a 454 cu. in. Chev at 650 hp. Nor does it matter if it is at 3500 rpm or 8500 rpm for the maximum horse power.

Changes to compression ratio, cam, carb, valve timing and duration differ for each case. What is good for the low end torque and horse power is BAD for the high horse power and high rpm and vise-a-versa. It is sure nice to read here how to tune the best for my type of low speed Land Rover driving. What is missing in this discussion is reference to the gasses themselves and the part they play in the power/ torque formula. The gasses (not gasoline or lpg but oxygen, nitrogen and such, you know, the airy sort of gasses), their movement and the theory (formulae?) are the same for both power objectives.

In short gasses have a mass. A mass once moving will continue to move until some force is applied to it to stop it. We all learned that in school. The piston on the down stroke of the intake stroke starts to create a vacuum and gasses are drawn into the cylinder, quite quickly. A force has been exerted on this mass of gasses and they will continue to move till an equal impediment is put in their way, like the valve closing. BUT when the gasses really get moving at a good clip and just before the valve closes the inertia of the moving gas drives it into the cylinder and can increase the pressure over what the simple intake stroke of the piston would draw in. The trick is that you need a column of gas and for it to move at a certain rate of speed to optimize the inertia from the velocity it has developed. Once this column of gas is in motion it continues to pressurize the intake manifold till pressure is built up to stop its forward movement. By then, the intake valve on the next cylinder should be opening to accept this increased pressure and the benefits of the inertia of the continuing column of gas.

The harmonics (I think that is the term used here.) , volume of the cylinder and frequency (rpm) can be used to arrive at a formula for the length of the column needed for optimizing this phenomena. I can’t remember it right now and would have to look through some books to find any reference to it. The formulae lead to the optimum length from the inlet valve to the open air or air chamber (air cleaner or plenum), this length or it’s multiples are the ideal for intake manifold length including carb and head. I suspect that is why some carbs seem to have peculiar sized spacers under them instead of just a gasket. Landy of course has adapters, but maybe they are to engineered specs. Also included in the calculations is the diameter of the column of air as I seem to recall the optimum speed is something like 300 feet per minute. So it isn’t just length but diameter as well to accomplish a peak velocity at a target rpm.

If a peak cylinder loading is wanted at a different rpm the numbers and resulting dementions of the intake system would be different.

The same sort of thing applies to the exhaust gasses. They have momentum and want to keep moving once started. The inertia from the exhaust gasses from one cylinder can be used to start to draw the gasses out of the next cylinder so the piston doesn’t have to push all the gasses out. This is why gas extracting exhaust manifolds have the peculiar bends in them, to equalize length and join one with the preferred next in the firing order to optimize gas flow (drawing it out). For the peak performance on the exhaust gas side, a target rpm must be chosen and calculations done to determine exhaust pipe diameter to optimize inertia from the velocity of the gas through the exhaust pipe. 300 feet per minute is, I am sure, the velocity preferred here. 300 fpm may not be the right figure for the intake velocity.

A low target rpm for peak torque would indicate a small diameter exhaust pipe. Like stock Land Rover has. I wonder if they calculated this into their power formulae or just had a pile of puny pipe they had to use up?
Higher rpm targets would require larger diameter exhaust pipe.

Now that I have installed a 2 inch exhaust system, I wonder if I would be better off with a smaller one as a lot of my 4 wheeling is low speed? I guess I’ll have to experiment with that one unless someone has a rolling road in their back yard and can do a lot of experimenting for the rest of us.

This also makes me wonder if a snorkle of the correct diameter and length will improve performance by more than just doing away with the oil bath air cleaner.

The End

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