Heads & Casting Days

[Keith #10324]

For restoration accuracy, what is the maximum number of calendar days cylinder heads can be cast prior to my engine's casting date of 11-18-58 and my engine assembly date of 11-20-58? Also, are there any differences between the 3755550 heads used on a passenger car and a Corvette? If so, how can you tell the difference(s)? This information will help in my search for a correctly dated/ matched set of 3755550 heads for my 1959 Corvette.

[Joe L.]

Re: Heads & Casting Days

Keith----

By NCRS/NCCB rules, I believe that the head casting dates can be up to 6 months (approximately 182 calendar days) prior to the engine assembly date. In reality, they were likely a lot closer than that. In your case, I would expect that the heads for the block would have been cast in early Novemeber, just like the block, but you don't need such heads to be "correct".

The GM #3755550 CASTINGS were all the same. However, they were machined into several different finished part number heads. Some, but not all, passenger car finished heads had 3 drilled and tapped holes on the ends. The heads used for Corvettes did not have the holes drilled and tapped. I could see where a passenger car head with the holes could be "converted" into a Corvette-configuration head by carefull filling, grinding and finishing of the head end surfaces. I'll bet more than a few out there have been so-converted.

[Keith #10324]

Re: Heads & Casting Days

Hi Joe-

Thanks for your response.

Regarding your response concerning the differences between the 3755550 passenger heads and the 3755550 Corvette heads, I thought I read somewhere that Corvette heads were cast at the Central Foundry Division at Saginaw and the Corvette heads had machined finished ends. Is there any truth to this information?

[John H.]

Re: Heads & Casting Days

My references may be incomplete, but I only show 1959 usage for the 3755550 heads, which was ten years before passenger cars used the "new" heads with machined ends and drilled/tapped accessory drive bolt holes when they went to the "long" water pump accessory drive system.