[steve]

actually the distributer advice was from a similar thread about detonation in a 455. i was also wondering if a worn vaccum advance pod could cause pinging under load if iit kicks in too early or too much ?

[Malky]

A couple of things worth checking that are relatively easy to do before you start tearing into the engine are the centrifugal advance as suggested above and the secondary rod size.
You need a dial back type timing light to check the advance. The ideal seems to be about 20 deg all it at 3000 rpm. (This is 20 deg on top of the static setting.) If weak springs are allowing it to come in earlier, that will not help.
The secondary rods and hanger can be removed easily, with the one screw in the middle of the secondary bores. Post the letter ID on the hanger and the two letters stamped on the rods. Emissions carbs ran very lean on the secondaries.
The above might help, but with 12:1, cast iron heads, 2.41 gears, and a relatively mild cam, I think you are stuck with using race gas.

[Philcol]

Mix 93 pump with 112 race at 1 to 1 ratio.

Phil

[speedshopmike]

bigger cam will just make *more* cylinder pressure at higher rpm due to better filling; that's where your problem already lies.