2.5 head on Eta Block?

Post Wed Mar 29, 2006 5:35 pm

Whats wrong with putting a 2.5 head on Eta Block rather than a 2.0?

Post Wed Mar 29, 2006 5:57 pm

the 325i head is shaped for the domed pistons in the 325 block, basically the 2.5 pistons have a wedge in the crown that protrudes into the combustion chambers.

the ETA head and 320/323 heads have a kidney shaped combustion chamber designed to work with a flat crown piston

combining the two gives roughly the same compression ratio but due to the differances outlined above , the squish band is affected making the combo slightly prone to pinking @ high loads.

Nothing a chip wouldn't sort though.

Post Wed Mar 29, 2006 8:24 pm

theres a guy on the 5 series forum who says the thing about not using the eta head is a myth. He says the misinformation comes from because the american etas run silly low compression and when u add an 325i head it doesnt work well. (not done it myself, so im merely passing on what hes said)

I believe mr everett has a running engine using eta block and 885 head.

Post Wed Mar 29, 2006 9:51 pm

He's sold it

Nick, can you look in the FAO section ASAP

Post Thu Mar 30, 2006 1:33 am

Ant wrote:Nick, can you look in the FAO section ASAP

all under control m8.
i had an email direct.
ive asked royal mail to track it and find out where it is.

Post Thu Mar 30, 2006 2:16 am

Chaos wrote:theres a guy on the 5 series forum who says the thing about not using the eta head is a myth. He says the misinformation comes from because the american etas run silly low compression and when u add an 325i head it doesnt work well. (not done it myself, so im merely passing on what hes said)

I believe mr everett has a running engine using eta block and 885 head.

american ETAs have different pistons pre '88 and had a compression of 9.7:1 i think and the '88 and up or super ETA had a 10:1 compression. This means you can use and ETA block but pre 88s need the post 88 pistons or custom