Firstfives.org

I realized that the head cc size was not in the cylinder head faq and so i measured my head cc today and got an average of around 63 cc after doing 2 different cinders a couple times im guessing stock heads have a head cc of 65 (same as b35) but since my head has been re-milled twice its slightly lower. I have a early head off a 79 528i but the casting mark is from a 78 so its a early head. just thought id let people know who are trying to measure compression ratio since i couldn't find it anywhere on the internet.

My sources, a pair of engineers I very much respect, give pre B35 combustion chamber volume at either 58 or 59 CCs. B35 at 65 from both. I can't find my preferred one at the moment, but here's one chart.

http://e28-535i.com/upload/M30_CR_Calcs.xls

After doing some more trials but with it sealed better and better equipment i was getting on average of 57-60cc for each cylinder. After talking to someone els who modifies m30's he said that all m30 heads have the same cc exept the b35 meaning the e12 head should have around 58cc but i think it can vary slightly, I am not using the best equipment i just wanted a general number since i was unable to find anything about it, but it seems to be more towrds the 58cc rather than the 65. Also thank you Mike that is a great resource.

adam_torrence wrote: Fri Jul 17, 2020 3:32 pm After talking to someone els who modifies m30's he said that all m30 heads have the same cc exept the b35

Correct. Heads did evolve some, but the valves and combustion chambers stayed the same until the B35. They were shocking similar for almost 20 years which is testimony to how good the original design was, even if it's not highly regarded anymore.