Hi perf 327 factory head gaskets

[Duke W.]

I and another '63 original owner both found upon disassembly or our 11.25:1 CR 340 and 360 horsepower factory assembled engines that they were put together with two thin (.015"-016" compressed) steel shim head gaskets. Does anyone have any data as to when this practice began and how long it was continued? The additional gasket would cut the CR about half a point. Did the practice continue with 11:1 350s? Also, was this practice used with 11:1 big blocks?


Duke

[Loren]

Re: Hi perf 327 factory head gaskets

Don't know about 350 or BB, but on your cars, if you wanted to GET to 11.25, you had to remove the head and remove one of the steel gaskets - call it creative warranty protection.

[Wayne M.]

Re: Hi perf 327 factory head gaskets

Duke -- If you want more details, check the Tech Service Bulletin, Jan 2, '62, (RESTORER Vol 7, # 3) dealing with detonation, pre-ignition and dieseling in '62 Corvettes with RE and RF code engines. Starting with '62 VIN 1871, or Flint engines dated F1020, they added 2 gaskets to each head, because "super premium" was not available everywhere (yet). It lowered compression to 10.5.


Loren has confirmed that they carried this into 1963 production. Somehow, I don't think this "fix" carried over to the "30-30 cam" era of '64/65; others may wish to add on this.

[Duke W.]

Re: Hi perf 327 factory head gaskets

Thanks, Wayne. The 30-30 cam had considerably more overlap than the Duntov, so it could take more compression without low speed detonation. Also, Chevrolet revised the centrifugal and vacuum advance curve during the '64 production run. In particular the centrifugal advance was brought in much quicker - full advance at 2350 crankshaft RPM versus 4600 in '63. Quicker advance would tend to increase detonation. Was it the cam or extra head gaskets that allowed the quciker advance? So can anyone tell us about the production head gasket configuration for '64 to '65 RE and RF engines?