Is it true that the 4A-C has a compression ratio of 8.8:1 and if it is what is the easiest and cheapest way to bump up compression, without going down the forced induction route. I realise that this will be illegal on my car as I am on my P's but will the boys in blue be able to tell?

Shave the head.

I have got it listed as being 9:1, I would either get a bigger duration cam or shave the head, What fuel you running.

Shell V-Power

Bump the compression upto 9.8 to be safe.

 

Its in the FAQ somewhere, 91 octane 9.1 compression aproxx, 98 octane 9.8 compression ratio.

Edited May 7, 200719 yr by AE70

i thought the standard compression was 8.6:1 either way it is very low, yes shaved head and a thinner head gasket will raise compression. 4ac's are surposed to run on 97 octane fuel acording to my owners manual.

Do a compression test this will give you an exact figure on your motor.

 

Also shave the head easiest way abotu free to $50 if you remove the head and take it to a shop so pretty cheap.

 

BUT if thee motor is worn and the rings are well used shall we say a shaved head will kiss the motor good buy after a short time seen it happen so just play safe don't try to pass 10:1 you will only do more damage.

 

Cameron

how much would shaving the head/thinner head gasket change compression..?

as much as you want it too ;)

i mean will 3mm raise it to around 9:1 etc?