[Peter Serio]

In 1966 and 1967 the recommended red-line RPM limits for the 4bbl version of the OHC6 engine was indeed 6,500 RPM. The rally gauges for a car with that engine reflect this as in post #2 above. What some people forget is that after 1967 Pontiac changed the way the crankshafts were made, or heat treated or it may have been the grade of steel those were made out of, starting 1968 including 1969 (the last year for the OHC6 engine) the RPM limit for the 4 bbl version of the cars with an OHC6 engine was downgraded to 5,500 RPM.

What is funny to me is that I see modern reproduction hood tachometers being marketed today with V8 electronics but the RPM red-line at 5,500 mis-represented as V8; Ram Air, RA II or RA4 tachometers which they are not! As far as I am aware all Lemans & GTO V8 engine cars from 1966 up to 1972 and with a factory tach (either hood or dash mounted) were clearly labeled with an RPM red-line starting at exactly 5,100 RPM.


The 1970-4 trans am tachometer dial does have a slightly higher re-line than an A body car, I am not 100% sure why as in 1970 that car would have come with a 400 RA III engine in it; same as would have been standard in, say a 1970 GTO Judge.