2.25 petrol power mods

[army2a]

Hey guys, does any one have any ideas on getting a bit more power out of a army 2.25 petrol engine? I know it will never be a powerhouse but any improvements would be great!

[isuzurover]

There are lots of options.

I had extractors, a decked block and decked 8:1 compression head on mine - raising the compression to ~approximately 8.5-9 :1. It went very well and I was happy with it. It was faster than my father's stock 2.25 with twin barrel webber from a 2.5L (incl large bore 2.5L manifolds).

My 2.25 would wind the speedo off the clock if I let it ~75 mph in a 109! It would ping if you lugged it but no worse than most petrol engines.

I knew an engine recopnditioner who had a 2.25 that was running over 9.5:1 compression and heaps of other modifications. It was even faster, but he had to run it on LPG to stop detonation issues. He eventally swapped it for a stock 3.5 V8 which was faster ;).

[series3]

I have extractors on a fresh 2.25 and it does give a little more power. It certainly holds it's revs up inclines better. I think there are some on eBay at the moment.


What sort of carb are you running?

Pat303 did head work on a 2.25 with good results I believe, but I don't know the details.

Isuzurover, dis you get those speeds with stock gearing and an overdrive? Big tyres?

[d@rk51d3]

Changing the fan for a civvy 4 blade, will give a little more response too.

I also recall on my Niva, we changed the timing chain shoe for an idler sprocket.
That opened up the rev range a bit. I wonder is something similar is available for the 2.25?

[isuzurover]

Isuzurover, dis you get those speeds with stock gearing and an overdrive? Big tyres?

I recall that at the time I had:

235/85-16 BFG trac edge tyres on disco steel rims
Standard (high range) gearing
No overdrive (but I think I installed one later - didn't change the top speed).

This is a much later pic from driving across the nullarbor (2.25D, 33's and no OD!!!), with a fair load on. I had a bit more accelerator left, but that was as high as I was willing to push the poor 2.25D. Note that speedo is 100% spot on (by GPS) with 33's.
https://www.aulro.com/afvb/images/imported/2011/11/278.jpg

With the 2.25P I think the fastest I had it was about the equivalent of 5 mph past the 75 mark. So ~80 mph. That was on a flat, straight road (Newell Hwy I think...). Needless to say it was certainly screaming with no OD! The rear main seal failed on the return trip, however I am sure that was due to a poor quality part, rather than the revs!

[series3]

Sweet lord. I think I baby mine a little bit... On 7.50 16s I sit on 90 km. I would never think of cracking triple digits...

[Blknight.aus]

foz holds the dollar on a 2.25D running anything thats this side of sweet lite crude to virgin olive oil and will get to 105 before running out o puff on the flats.

the 2.25P responds well to port matching the inlet manifold and a decent set of extractors if the extractors are tuned to about the 2.5-3k rev range.

[JDNSW]

The point perhaps should be made that with the exception of increasing the compression ratio, all the methods of increasing power work by getting more mixture into the combustion chamber. This engine/vehicle combination is fairly thirsty anyway, so this thought might give pause to plans to up power. (except for increasing compression, which should be the first action, expecially if you have a 7:1 engine - most of them.)

John

[isuzurover]

Sweet lord. I think I baby mine a little bit... On 7.50 16s I sit on 90 km. I would never think of cracking triple digits...

The 2.25 is undersquare (stroke shorter than bore diameter). No reason it can't rev if it is well balanced.

[JDNSW]

The 2.25 is undersquare (stroke shorter than bore diameter). No reason it can't rev if it is well balanced.

In my experience the 2.25 is very happy to rev, and as you say, if nothing is out of balance there is no problem. Noticeable improvement on mine when I took the military fan off!

John

[army2a]

Thanks for the input guys. Mines got a stromberg on it at the moment but seems to be very heavy on fuel? What are the best carboys for these 2.25 engines? Would bolting a civilian head on my army engine be a worthwhile option? Thanks heaps

[JDNSW]

Thanks for the input guys. 1. Mines got a stromberg on it at the moment but seems to be very heavy on fuel? 2. What are the best carboys for these 2.25 engines? 3. Would bolting a civilian head on my army engine be a worthwhile option? Thanks heaps

1. These engines are fairly heavy on fuel anyway for a variety of reasons, usually not to do with the carburetter. First thing is to ensure everything (ignition, timing, cooling, brakes, tyres and pressures as well as carburettion) are up to spec.

2. The best carburetter is one in good condition, and preferably one of the ones that were designed for the engine. As far as performance/economy goes I see no difference between the Solex and Zenith, but the Solex probably gives less trouble but is harder to find parts for, and its operation is harder to understand. The Weber I am less familiar with, but it is said to give slightly better economy, at the expense of slightly worse performance. I have seen accounts suggesting that the SU gives best performance by a considerable margin, but requires a special intake manifold. The Stromberg, even if correctly jetted for the engine, which it may well not be (and in good condition - unlikely, since it will be a second hand one off a Holden) is second rate, if only because it is not capable of maintaining mixture when on a steep slope. The only reason these were ever fitted is because a second hand one off a Holden was easier and cheaper than fixing the Solex or Zenith.

3. There is no difference between the civilian and military head. There is an older style of head, which will be 7:1 and a newer one which may be either 7:1 or 8:1, but most likely 7:1. With the earlier head it is only safe to plane off a very small amount, raising the compression to perhaps 7.5. The newer head can be raised to at least 8.5 and probably 9 without problems, although at 9:1 you may have problems with ordinary unleaded.
The distinguishing feature of the newer head is that if you look on the top of the head, adjacent to the carburetter between it and the rocker cover, you will find a square boss cast into it about 2cm across. This is absent on the earlier head, and should have stamped on it either a 7 or 8 denoting the compression. If unstamped (it may be faint) it is 7 - unless someone has already planed it and not changed the markings.
The vast majority of the 2.25 engines sold in Australia were 7:1. One other point - I have heard that the later head, especially when planed, can allow the bit below the thermostat housing to hit the early water pump - but can be corrected with a light touch with an angle grinder.

Hope this helps

John

[87County]

1. These engines are fairly heavy on fuel anyway for a variety of reasons, usually not to do with the carburetter. First thing is to ensure everything (ignition, timing, cooling, brakes, tyres and pressures as well as carburettion) are up to spec.

2. The best carburetter is one in good condition, and preferably one of the ones that were designed for the engine. As far as performance/economy goes I see no difference between the Solex and Zenith, but the Solex probably gives less trouble but is harder to find parts for, and its operation is harder to understand. The Weber I am less familiar with, but it is said to give slightly better economy, at the expense of slightly worse performance. I have seen accounts suggesting that the SU gives best performance by a considerable margin, but requires a special intake manifold. The Stromberg, even if correctly jetted for the engine, which it may well not be (and in good condition - unlikely, since it will be a second hand one off a Holden) is second rate, if only because it is not capable of maintaining mixture when on a steep slope. The only reason these were ever fitted is because a second hand one off a Holden was easier and cheaper than fixing the Solex or Zenith.

3. There is no difference between the civilian and military head. There is an older style of head, which will be 7:1 and a newer one which may be either 7:1 or 8:1, but most likely 7:1. With the earlier head it is only safe to plane off a very small amount, raising the compression to perhaps 7.5. The newer head can be raised to at least 8.5 and probably 9 without problems, although at 9:1 you may have problems with ordinary unleaded.
The distinguishing feature of the newer head is that if you look on the top of the head, adjacent to the carburetter between it and the rocker cover, you will find a square boss cast into it about 2cm across. This is absent on the earlier head, and should have stamped on it either a 7 or 8 denoting the compression. If unstamped (it may be faint) it is 7 - unless someone has already planed it and not changed the markings.
The vast majority of the 2.25 engines sold in Australia were 7:1. One other point - I have heard that the later head, especially when planed, can allow the bit below the thermostat housing to hit the early water pump - but can be corrected with a light touch with an angle grinder.

Hope this helps

John

all good solid advice, JD - thanks

we're in the process of doing up an ex-mil 2a and I have seen the earlier posts with comments re extractors - as our exhaust manifold is cracked (but weldable I expect), I was considering getting extractors - have you had any experience with these giving any performance or economy improvement?

[JDNSW]

all good solid advice, JD - thanks

we're in the process of doing up an ex-mil 2a and I have seen the earlier posts with comments re extractors - as our exhaust manifold is cracked (but weldable I expect), I was considering getting extractors - have you had any experience with these giving any performance or economy improvement?

I have had no experience with them, but I understand they do improve breathing substantially.

The only concern I would have is that the loss of the hotspot could result in carburetter icing if you live in a suitable climate (temperature about -5-20, humidity above 80%), which I suspect you do. Most people these days have never encountered this, as the motor industry (by and large) managed to eliminate it in the 1930s by intake manifold heating, but you learn all about it getting a pilot's licence - it still remains a potent cause of engine failure in carburetted engines, to the extent that many aircraft have intake temperature gauges as well as controllable hot intake air. (The other fix is fuel injection, which also (almost) eliminates the problem) So I would have concerns about doing away with the solution to this problem. Of course, if you lived anywhere in most of inland or northern Australia, where it rarely is cold enough and humid enough at the same time, you don't need to worry.

John

[wrinklearthur]

foz holds the dollar on a 2.25D running anything thats this side of sweet lite crude to virgin olive oil and will get to 105 before running out o puff on the flats.

the 2.25P responds well to port matching the inlet manifold and a decent set of extractors if the extractors are tuned to about the 2.5-3k rev range.
Hi Dave

Do you have the calculations handy for determining those lengths?

Cheers Arthur

[isuzurover]

1. These engines are fairly heavy on fuel anyway for a variety of reasons, usually not to do with the carburetter. First thing is to ensure everything (ignition, timing, cooling, brakes, tyres and pressures as well as carburettion) are up to spec.

2. The best carburetter is one in good condition, and preferably one of the ones that were designed for the engine. As far as performance/economy goes I see no difference between the Solex and Zenith, but the Solex probably gives less trouble but is harder to find parts for, and its operation is harder to understand. The Weber I am less familiar with, but it is said to give slightly better economy, at the expense of slightly worse performance. I have seen accounts suggesting that the SU gives best performance by a considerable margin, but requires a special intake manifold. The Stromberg, even if correctly jetted for the engine, which it may well not be (and in good condition - unlikely, since it will be a second hand one off a Holden) is second rate, if only because it is not capable of maintaining mixture when on a steep slope. The only reason these were ever fitted is because a second hand one off a Holden was easier and cheaper than fixing the Solex or Zenith.

3. There is no difference between the civilian and military head. There is an older style of head, which will be 7:1 and a newer one which may be either 7:1 or 8:1, but most likely 7:1. With the earlier head it is only safe to plane off a very small amount, raising the compression to perhaps 7.5. The newer head can be raised to at least 8.5 and probably 9 without problems, although at 9:1 you may have problems with ordinary unleaded.
The distinguishing feature of the newer head is that if you look on the top of the head, adjacent to the carburetter between it and the rocker cover, you will find a square boss cast into it about 2cm across. This is absent on the earlier head, and should have stamped on it either a 7 or 8 denoting the compression. If unstamped (it may be faint) it is 7 - unless someone has already planed it and not changed the markings.
The vast majority of the 2.25 engines sold in Australia were 7:1. One other point - I have heard that the later head, especially when planed, can allow the bit below the thermostat housing to hit the early water pump - but can be corrected with a light touch with an angle grinder.

Hope this helps

John

I agree with all of the above. However the only thing I will add is that my father's 88" IIA with twin barrel webber mentioned above, always used more fuel than my 2.25 with zenith.

Despite rebuilds of the carby, head, a new distributor, and several tune-ups. The only thing I can put it down to was the carb. None of the other issues (brakes, etc) applied.

[Warb]

I haven't fully read it myself, but try:

Land Rover Performance Tuning - Power Plus - Land Rover cylinder heads, camshafts, SU Carb system, 2.8 engines - ACR - Automotive Component Remanufacturing Ltd (http://www.automotivecomp.com/landrover_perf.html)

It's basically a list of parts they can provide, but may give ideas about where to start.

From experience (not on LR's) the HIF SU's are very good carbs, I've found them to be better than the HS's, and the HIF44 can cater for outputs up to 140bhp+ whilst providing good flexibility and economy.

[chazza]

I read an article some time ago by a chap in the UK who fitted an Eaton supercharger to his 2.25P and was aa happy as can be with it.

The blower came from Ebay and before that a Mini and was very cheap. The low compression Rover engines are suited for blowing.

If anyone is interested, I recommend reading Allan Allard's book on supercharging and turbocharging cars,

Cheers Charlie

[JDNSW]

I read an article some time ago by a chap in the UK who fitted an Eaton supercharger to his 2.25P and was aa happy as can be with it.

The blower came from Ebay and before that a Mini and was very cheap. The low compression Rover engines are suited for blowing.

If anyone is interested, I recommend reading Allan Allard's book on supercharging and turbocharging cars,

Cheers Charlie

Actually this reminds me that I read many (probably forty) years ago about a supercharged 2/2a four cylinder petrol fire engine intended for a quick response airfield unit.

John

[series3]

Here is another place (In the UK) that have some 2.25 performance options as well

Land Rover cylinder heads 300TDI, TD5, LDF500160, LDF500170, 200TDI, V8, 2.0TCie Freelander diesel, turbo diesel, M51 BMW RR, 2.5 petrol, 2.25 petrol etc. (http://turner-engineering.co.uk/html/cylinderheads.html)

Sam