1957 Plymouth 230 Head vs the earlier 230/218 heads

[Dozerman51]

Here are some photo comparisons of a 1957 Plymouth 230 head as compared to a 1940’s Plymouth 218 head. Hope you enjoy them.

[greg g]

Drum roll please! The major difference to make more HP was Higher compression due to smaller combustion chambers.  The 57 head looks a lot like the Edmund's head that was near 9 to one compression depending on which engine it went on.

[Elwood]

1 hour ago, greg g said:

Drum roll please! The major difference to make more HP was Higher compression due to smaller combustion chambers.  The 57 head looks a lot like the Edmund's head that was near 9 to one compression depending on which engine it went on.

 

Perhaps I'm not looking at these correctly.  Assuming the lower head in the upper photo is the underside of the 1676337 head in the lower photo (the '57 through '59 Dodge and Plymouth 230ci car head), it looks to have larger combustion chambers than the other head, and would therefore have a lower compression ratio.  True, the exhaust valve pocket is smaller on the 1676337 head, but the transfer area is definitely larger.  I'd be really surprised if the 1676337 head produced 9:1 compression, even shaved 0.050".

Edited February 6, 2018 by Elwood

[Dozerman51]

The 1676337 head produced an 8:1 Compression ratio according to Mopar. I installed this head on my 230 and I could immediately see the difference in torque over an earlier 230 head I had on it. 

[Elwood]

Has anyone cc'd either one of these heads?  I'd be interested to know the combustion chamber volumes, and how much variance exists in volume across the six cast chambers in a head.