Reply to "cam and compression recommendations"

With a Pantera it isn't that easy to hear the engine ping because of the location.

The real danger with it is if pinging becomes so extensive that it acts as misfiring.

The issue with detonation is as much with the combustion chamber shape as it is the actual static compression ratio.

The closed Cleveland shape does not lend itself well to low octane fuels, i.e., it tends to detonate easily.

Interestingly enough though, the closed chambers on the 289hp iron heads with a 10.5:1 static ratio do. They easily run with "regular" gas with no decernable detonation.

I think the solution to detonation with the closed chamber Cleveland heads is in the camshaft timing.

I think the modern aftermarket "performance" cams are leaving the exhaust open longer to blow some of the compression out of the exhaust.

That is a number that you need to leave up to the cam grinder. You could in effect lower the pressure in the cylinder the equivalent of a point or more by changing the timing events.

That's all too complicated for me. I leave that up to the witch doctor making up a voodoo camshaft design.

The complication to all of this now, is there are aftermarket heads available with their own combustion chamber designs. This effects flame travel and propagation and other factors which all effect sensitivity to detonation.

I noticed one thing with my A3 heads. First they do respond very noticeably to "indexing" of the spark plugs. Secondly, the colors on the porcelains clearly indicate a dividing line in the combustion chamber itself point to the location of the exhaust valves, black-brown, and the intake side, clear- tan.

I have never seen this on any other engine. To me, this is stranger then the South Seas Anomalies.

I do remember that when I ran the 12:1 TRW pop-up pistons, there was a "fire slot" in the dome.

It was said to be worth 8hp stock. I do remember people like Don Nicholson being on record as stating the shape of the piston dome, to him, was the key.

There were pictures of the domes on his pistons as he massaged them in articles in magazines like Hot Rod, back when he was running the 351C in Pro Stock.

I would also say that he was probably running 14 or 15:1 compression ratio with 115 octane gas to get his 800 hp out of basically a massaged stock specification 351 in Pro Stock.

Those other combinations that you saw like the aluminum block and heads were for match racing where there were few limitations.

The Pro Stock engine was the D2AE-CAN 4 bolt block with the D1AE iron Boss heads.