Re: V-8 head part nbr vs cast nbr

Posted by Jack Vines On 2008/9/17 14:07:21

OK, I've got a half-dozen 374"s so I should be able to find one on which the head casting number is readable. I'll be going up to my shop where they are stored later this week.

Let's start over on the 320" heads:

1. Were the machined 320" heads a different casting number than that of the 352"? It would have been relatively easy operation to make the machined combustion chamber 8cc larger. The as-cast chamber is what it is.
2. Has anyone seen any info to indicate when the 320" change was made to as-cast, did the valve size and/or compression ratio also change? That it was necessary to change the carburetor and distributor may have been necessary due to a higher compression ratio. Why else change those components?
3. Does anyone have a set of as-cast 320" heads. It would be interesting to check the CCs to determine if they are different from the machined heads.

As to why the change from machined to as-cast combustion chambers:
1. I doubt it was for cost savings. Machining was a simple one-pass with an end mill. It was more costly to change the pattern, pour the test castings and make the checks and remove the machining operation from the line than to leave it in place.
2. My opinion is it was the easiest way to raise the compression ratio. They just made the chamber smaller by changing the pattern to add more iron.
3. The smaller chamber also slightly shrouded the valves. This is probably why the change to 2" intakes.

Now that we're getting some traction on head casting and part numbers, how about crankshafts? In theory, with three different bore diameters and piston weights, there should be three different part numbers. Then there's the Unobtanium forged crankshafts, so six part numbers. I've never seen a casting number, forging number or part number visible on any Packard V8 crankshaft. How do we know what we should have, much less what we've got?

thnx, jack vines