Offenhauser Heads 375/400/425

[Matt6494]

Hi All,

Looking for some advice on upgrading my currently standard 8CM Flathead.

I'd like to get some Offenhauser cylinder heads, and have seen they come in 400/425 new, or sometimes some older 375s come up.

What would be best for a stock 8CM engine?

I've got hold of the Flathead compression chart by James Leis that does the rounds on various forums.

It looks like on my 255ci engine the compression ratios would be 8.15 / 9.28 / 8.9 respectively for 425 / 400 / 375.

Interestingly these are different to those listed in the Offenhauser catalogue, these being 8 / 8.5 / 9.

I'm also planning on fitting a matching Offenhauser dual intake and 2 97s of this makes a difference to selection?