rockind78

Glenn,

i had a question for you if you don't mind. I was reading in one of your posts (I believe it had something to do with an '86 305 motor) that your were stressing timing as actually a pretty good tuning tool (when you get into the PROM??). Anyway, you mentioned something to the effect of removing edges in the cylinder head to reduce detonation sensitivity. I was wondering if you could elaborate a little more or at least point me in the right direction, either in doing it myself or what I should be asking the machine shop for. Thanks for your time.

Grim Reaper

You want the combustion chamber as SMOOTH as possible. No sharp edges of ANY kind. Run your finger along the edge of the "half moon" of the combustion chamber where it meets with the surface of the head (that will be flush with the block). It will feel sharp. Almost to the point that it could cut your finger. Radius all edges.

Inside the combustion chamber, smoothen as much as possible. It isn't neccesary to be "polished", but the more the better.

I wish I had taken a picture of the "raw heads". You could feel the roughness of the surface of the combustion chamber and you realize all those sharp little spot will act like a "glow plug".

Also, there is a protrusino around the spark plug like a small cube (on L98 heads). Again, remove those sharp edges. The bottom line is "the smoother the better". You don't even have to do any porting (I'm avoiding that subject like the plague), just smoothen the combustion chamber. If you have a scan tool, you'll be amazed on the extra spark advance you will be able to run.