Thread: Getting the most out of a 2.25 petrol

headers and a cam grind....

I have a 3-bearing engine that is then obviously a 7:1 CR.

How much should be taken off the head to get it to 9:1 and I assume then I'd have to run 93 octane minimum? Should I rather go for 8.5 :1 or even lower?

This is a slippery slope

I knew a guy who was an engine builder who shaved his 2.25 to 9.5+:1 and installed a better cam and extractors. He claimed he could only run on LPG with out pinging... (this was pre 100 RON fuel though)

In the end he replaced it with a stock 3.5V8 from a stage 1 (the lowest output 3.5 ever made). He then lamented all the time and money spent on the 2.25...

That said, back when my IIA was a 2.25P I had a shaved head ~8.5:1, extractors and a reco'd zenith. It would wind the speedo off the clock on the highway (>75 mph). Despite being fitted to a heavy 109 it was faster than my dad's 88" fitted with 2.5P manifolds and a weber 32/34 DMTL.

Just bear in mind that the 2.25 with its design (e.g. poorly shaped combustion chambers), will never be a quick engine compared to most 4cyls and will be prone to detonation.

p.s. - if you go down the path of cam mods, be very careful who you get to do the work. If not careful you could end up with a much less usable torque curve. Most cam places don't do many 4x4s...

Speaking for myself, I'm not thinking of going too mad on the mods.

Maybe a head skim to 8:1 CR and a Britpart Electronic Ignition module.

Custom Headers/extractors will maybe be fitted later, but I'm wary of these as I find most guys build them for revs and not increased torque.

Personally, from experience with my 76 SerIII 88 (should be the same set up as the Game with emission control etc) I'd try a good set of extractors and free flow exhaust before anything major on the motor. I had big rubber on Sunraysia's and it used to go pretty well on road, but it was axle snapping territory also (and crown wheel), so you do need to be careful.

If I ever get it back on road I'll be doing the electronic ignition also.

Cheers
Lakey

My 2.25P has a Weber twin barrel that's set up to only setup to run one barrel until you put your foot to the floor, a set of Genie extractors and upgraded coil and fairly new leads, plugs and dizzy cap. It has better top end after the extractors but didn't improve the low down, the engine is pretty knackered and the rings and valves are very leaky, I reckon a good exhaust maybe a cam upgrade but if your engines a bit worn out a decent rebuild would do wonders and gives you a better base to start with. The problem with increased compression ratio is the cost of premium fuel, you can buy octane booster but I don't think it'd be any cheaper and 2.25P's aren't very efficient with economy figures up to 20L/100km.

I'm not absolutely sure of this, but I think that all the GAMEs would have been built with 8:1 engines. To find out if yours is an 8:1, on top of the head half-way along the manifolds side is a raised boss. Clean this top face and you should see a large '8' engraved in the surface. There is also an engine number reference on compression ratios, though it may not still be relevant with past repairs and mods.

The 7:1 engines were apparently much lower powered and worse on fuel.

Dan.
69 2A 88" pet4 (still in disguise), 68 2B FC pet6 (still resting quietly), plus 14 other project/parts cars (1xS2, 6xS2As, 7xS3s).

Thanks for all the advice so far.

The engine in the GAME atm has a engine number of 90177997b

I found this website http://www.glencoyne.co.uk/engno.htm

It seem to suggest that it is a 8:1 3 bearing engine...

is that correct?