2.5 Head question

[MODXR6]

What is the difference in the following heads? Reason I ask is I see no difference whatsoever other than the casting number. I know what they are supposed to be for but can find nothing different in any of them.

18488-C3 (promax 225)

18488-C4 (promax 150/stock 2.5)

18787-C4 (2.0)

[Vecman]

The combustion chamber sizes are different between the
C2, C3, and C4. If you use a dial caliper to measure across
the chamber you will see. The C2 heads have smaller chambers
2.190 I believe and C3 2.230 from side to side I believe and so on.

Vecman

[MODXR6]

Should the depth be the same?
Is there a problem using the 2L on a 2.5? Everything else matches up

[Vecman]

Mod,
I haven't tried to put a set of 2.0L heads on a 2.5L.
It's probably me but I like the C2 heads the best.

Vecman

[Scott in MN]

I have a set of the c4 heads and they cc'd out to 33cc's if I remember right. I am having them cut and they should bolt right on my 2.5.

[86vintage]

The CC's of the heads is what establishes the cranking compression ideal they say 35cc with high test gas. you can CC to a smaller volume to get better compression but you will need race gas
Have fun!