power pack heads
Dapper,
Welcome to the forum. I'll try to give you the short version of the aluminum head story so I don't end up rambling. Both of the '60 FI engines were to have aluminum heads with 1.94" intake valves and higher hp ratings. They were advertised and even people ordered cars thinking they were getting the heads. Never happened. They cracked between the valve seats and some even cracked during initial torquing. The '59 FI engines rated at 250 and 290 hp were carried over to '60 and the "Advertised Maximun Engine Performance" chart was revised in June 1960 to show this. There were only a few engines built at Flint with aluminum heads and they were sent to Warren Tech Center for testing.
There were no Corvettes delivered with aluminum heads by the St. Louis plant. The rumors of cars being recalled because of aluminum heads cracking are false and just rumors. Since there were no heads delivered there were none to recall so there is no service bullitin relating to this subject. This is varified by a letter from Joe Pike (Chevrolet Asst National Sales Promotion Mgr. and later Corvette News editor, from where most of us knew Joe) dated August 1961 stating that "There were no 1960 or 1961 Corvettes produced with aluminum cylinder heads." The letter further states the use of the '59 engines in the '60 FI car and the new 315 hp engine in the '61. This '61 engine had an iron version of the aluminum head with the double hump marking on the end.
You will see some of the alum heads in private hands as they were cast by Chevrolet and other sources including Alcoa in the mid '60s for use in an Indy engine project. All seem to have the '59 casting dates that were in the molds. I don't feel that these heads would be good for anything except a display novelty. They would crack if you tried to use them and they wouldn't be correct on a restoration.
But you asked about Power Pack heads, didn't you? In the passenger cars the 265 and 283 inch engine were standard with low compression heads and a 2bbl carb. When given the higher compression heads, 9.5 on the 283, a 4bbl and dual exhaust they were called Power Pack. They were listed as such in the advertising also. The Power Pack 283 was available thru '66 in passenger cars. It was used in the Corvette through '61 but not called Power Pack since it was the base engine and not an option as in the other Chevrolet lines.
These Power Pack heads were also used on the 250 hp 327 " engine available through '64 in Corvettes and Chevrolets. They carried 1.72 inch intake valves and 1.50 inch exhausts and were marked with a small pyrimid on the end. All '60 engines used the power Pack head 3774692. '61 Corvettes also used casting number 3774692 on 230, 245 and 270 hp engines. The '61 275 and 315 hp FI engines used casting number 3782461 with the 1.94s.
The '62 to '65 327/250hp used Power Pack head casting number 3795896. The '62 through '64 higher hp 327 engines used either a 1.94 or a 2.02 intake valve head depending on the hp rating.
I hope this is what you needed to know. If I can be of further assistance let me know.
Tom