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I have a set of cast iron heads. The outlet valve to the heater is attached to the right water inlet.

I also have a set of HC aluminum heads and they have a port near the right rear of the engine, that looks to be for that application.

I did some visual research and it looks like earlier (pre '38) cars have the heater valve off of this port.

My question is, for the '30's V12's were all the aluminum heads the same, except for compression ratio?

Also when did the factory start producing the cast iron ones?

Cast iron cylinder heads date back to the introduction of the Twelve as the Twin Six in 1932.

Sorry, can't help with the other questions.

Thanks for the response. It is curious that the production of cast iron and aluminum heads were parallel. Begs the question, WHY?

Packard was having cooling problems with that engine from the introduction. The project was on a rush schedule. Higher compression ratios increase the burn rate which reduces the heat load on the cooling system.

A lot of those - probably most - of those cast iron heads are aftermarket.

Tim,

My cast iron heads were put on in the early '70's I think. I haven't looked for any markings on them.

Thanks for the help.

Bill

Here are the combustion chamber difference between the HC aluminum and the cast iron heads.

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Here is the heater outlet comparison. On the right is the cast iron with the tap off the water inlet. The bule pen is in the port on the aluminum head.

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