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Originally Posted by 73T/A
If you actually go back and read my original post you will see that I never mentioned the year 1970 RASD cylinder head I don’t know were you came up with that.So no confusion on my end.
I would think that if one was developing the 455 SD head that the 1971 455 H.O. head would be a good one to use to get porting flow data.It has the same 111 cc combustion chamber as the 455 SD and the 71 455 H.O. 197 head has better exhaust flow than the 1972 7F6 head right of the bat.The 7F6 head has a restrictive exhaust port (information from page 47 Pontiac Engine Design & Blueprint Assembly book).Craig Hendrickson& Kern Osterstock.You say that the 7F6 head was a improved.In what area just curious.Also you mentioned that the heads being disused just have four 2’s and four 1’s.I guess you didn’t see the RUSS or work order numbers stamped that was mentioned.If you have some pictures of any of the numerous heads that came through from Pontiac engineering myself and others would love to see them for future reference.You mentioned about the exhaust ports on the 197 heads being discussed as all hogged out.I would think gasket matched but not much if any beyond that.I am using stock Ram Air Restoration exhaust manifolds with factory metal gaskets with no overhang in the ports.Also using a untouched factory 1971 455 H.O. intake using stock port Felpro 1233 gaskets.
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I'm well aware you mentioned RUSS and a work order number. None of that indicates those numbers mentioned would have matched up with numbers from Pontiac Engineering. Only the twos and fours look like something they might've done.
The SD head was turned over to production about the time your heads were cast. There'd be zero time to send them to be ported, returned, evaluated and Dyno tested. I brought up the RASD head as that's the only 197 head made with an 87 CC chamber. You mentioned your heads were probably smaller than the measured 92cc . I figured if they're not milled 111 cc chambers the only other option is the RASD. Or am I missing something?
If your heads have been matched to a factory exhaust gasket, it's an optical illusion they look larger. If your intake ports match a 1233 gasket they're smaller than an SD455 intake port.
The 7F6 is a redesign casting made with a different casting process. It's more consistent, has better water jackets, has induction hardened seats, a short turn which will work better than a 197 head and possibly an over the counter IV head, for competition use. The exhaust is not a restriction what so ever compared to a 197 head. But regardless the engineering department knew a ported RAIV head kicked azz. They felt like the SD head was better than the IV head. I'm quite certain if Russ wanted to put his name on a pair of heads it would've been a top shelf head..... Not a modified 197 when he knew he had several better choices.
It seems more likely RUSS racing engines in Florida stamped their name and order number on those heads. Especially since they came from Florida and RUSS operated in that State. It'd also explain the 3/8 studs .... GM engineering was using the 7/16 RAIV parts on their dyno engines, it'd be likely Russ would've continued the practice.