Compression ?

Post Tue Jul 25, 2006 11:34 pm

I've got almost all the bits for a spare 2.7 but i'm missing the pistons.
I have a spare M40 gathering dust and was wondering how well it would work if i got a couple of extra pistons and used those with the 2.7 crank

What i'm not sure of is the compression ratio because of the cup in the piston tops (and the pins) and would be graetful if someone could shed some light.

Cheers

Post Wed Jul 26, 2006 4:45 am

I have never seen the pistons on a m40 but i would guess that they will not work (just a guess please correct me if im wrong). The type of pistons you need depends on the head that you will be using. do some searhes on here you will find a ton of info on these 2.7's.

Post Wed Jul 26, 2006 11:48 am

thats the problem, i don't want to spend any money on it.
I want to build it with the bits i've got already, the M40 ones have concave top's not convex like the 525e or 325i so will run at a lower CR but i need to know how low. Then i can either shave the pistons or maybe the block

Ã‚£Ã‚£Ã‚£Ã‚£

Post Wed Jul 26, 2006 10:48 pm

Thats the block i was thinking of putting them in but don't want to fork out for shaving the block (and pully) to get the same pistons back in

I think i'll pull the M40 apart when i get a bit of time.

Cheers