Cylinder head combustion chamber volume

[Duke W.]

I'm consulting with a friend on a 327 engine rebuild. It has a 461 head on one side and a 462 on the other, both with the 1.94/1.5" valve set.

I found a spec for the 462s with the "small" valves of 62cc. The 461 should have slightly less volume because of the small spark plug side quench zone that is beveled on the 462 casting, but I can't find a nominal OE machined (not NHRA minimum) chamber volume for the 461 with the 1.94/1.5" valve set, but I figure it must be a couple of cc less.

Does anybody have a spec from a reliable source on the nominal OE machined chamber volume for 461s with the 1.94/1.5" valve set?

Duke

[Scott Marzahl]

Re: Cylinder head combustion chamber volume

From Colvin's book, the chamber size for a 461 is listed as 62.076 CCs, in 1966 when the 462 came out it is listed as 62.076 and for 462s made in 1967 the chamber size increased to 63.305 CCs.

However, if I look in Small Block Chevy Performance they are both listed at 64CCs.

Scott

[David B.]

Re:Cylinder heads volume

The 62cc number is correct for 462 heads, not the 64cc in the SBCP book. I cc'd my 462 big valve heads during a recent engine rebuild and they all came in at 62cc's. I have a set of 461 small valve heads but haven't cc'd them.

[Duke W.]

Re:Cylinder heads volume

Thanks for the info, guys. The available data is inconsistent. My FM Speed Pro catalog lists both 461 and 462 as 64 cc and doesn't distinguish between valve sizes. There should be two values for both 461s and 462s - with the standard and large valve sizes.

David - I have some recent data from an uncut set of big valve 461s with a little chamber rework and they were about 64cc. Have your heads been surfaced?

Right now my best guess is that the chamber beveling on 462s adds about 1 cc and the radius cut to unshroud the inlet on big valve versions of both adds about 2 cc.

Duke