Thread: 2.25 petrol power mods

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 .

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?

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?

Originally Posted by series3

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.


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!

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...

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.

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

Originally Posted by 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...

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