Re: V-8 head part nbr vs cast nbr

Posted by Jack Vines On 2008/9/17 10:43:10

Interesting and arcane info. I've never worked on 320" heads, but by my calculations, they should have 8cc smaller combustion chambers than the '55 352" heads if both have the same 8.5 compression ratio. The Hash engines with the 352" heads on the 320" short block had 7.8 C.R., so that also mathematically checks backward.

Questions:

1. What was the date of the service letter announcing the change from machined to cast combustion chambers? I had assumed the change was made to raise the compression ratio for '56. If so, why was the change made on the 320" engine which never had a published C.R. increase?
2. Did the service letter specifically state the change was only for 320"? All later 352" and 374" had cast chambers, but why would they only announce it for 320"?
3. Was the switch to 2" intakes made at the same time? The specs for all '55s I have seen in print are for the smaller valves, but has anyone ever seen a machined chamber with the larger valves or a cast chamber with the smaller valves?
4. Since '55 352"s had 8.5 C.R and the '56s had 9.55 C.R. (the '56 Hashes got the 9.55 C.R., but still only the two-barrel carburetor.) was the cast chamber phased in at model year change for 352"?

thnx, jack vines