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  1. 1964-1974 Tempest/LeMans/GTO Engine Tuning
    I'm having concerns with compression ratio limits to '69 #62 heads off a 428. So I bought a '70 400 to build and throw into a '68 Tempest. I was told the motor was stuck, but have found it's actually .30 over with new pistons, cam, timing chain, and crank. The heads are press in stud #16(I have...
  2. 1964-1974 Tempest, Lemans & GTO General Discussion
    Hello everyone. I recently purchased a 1967 GTO. The car originally had a 400ci with 335 hp “YS” code with an automatic transmission. However it now has a 455ci the engine based on the numbers next to the timing cover (starting with 22P) it was originally in a 1972 Pontiac. This 455ci has “YC”...
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