Ok, I'm really going to show my ignorance. I know what detonation is and what causes it. However, I keep reading all these posts which refer to pinging and I can't tell if my 327 is detonating or not, With the cams rough idle and the dual exhausts thumping, i don't think I could here a ping if it happened. Is detonation what caused the old "valve rattle" in my cars of the past when pulling a hill. I have read several articles on how to read plugs to look for the dark spots on the ceramic. its just that with my convertible and loud dual exhaust, the exhaust sound is loud enough to cover up any valve rattle that you could hear in hard top cars with very quiet stock mufflers.

Clyde

Clyde, my car is also somewhat noisey, but when I finally heard some detonation ( I think pre-ignition is the process) it was certainly 'valve rattle', like in rattle can. I've never seen it, although you'd really need a magnifying glass, but specs of alum/iron on the plugs tells you that.

I don't know why they call it pinging. It's a definite rattle. A little at part throttle is ok, if you hear it at full throttle pull your foot out of it quick. You'll often see a puff of white smoke as well at higher rpm as the carbon deposits are blasted off.

Yeah, it's the "valve rattle" you'd hear when "pulling a hill". That's often because your vacuum advance is still somewhat active.

It really sounds bad if you hit it during WOT, meaning your mechanical advance is going too far at higher RPM's. Almost sounds like your engine is gonna fly apart (and it well may).

I am no expert with engines but I will give you some advice from experience. When I put my motor in I was concerned that it would not run on pump gas because it had domed pistons and I had always ran 110 octane through it. I ran it in a circle track car and now it was just sitting around and I figured a 383 beats a 307 any day so I put it in the velle and ran 93 through it. I did not know the exact sound to listen for but I did not notice any sounds out of the ordinary ran fine for a 2 months but very little driving. Finally I heard a noise that I didnt like so I quit driving it. Tried several things and tested but never got better when one day I started it and it sounded like she was comin' apart :eek: I took the heads off and sure enough 3 pistons had chunks out of the tops of them. I usually learn hard lessons from my mistakes and I did not ask anyone on here before it was too late. Kind of a long story to get to the point but when I asked around here I was told that you may not always hear pinging and the pistons I had are known for breaking like mine did(From the top down to the first ring, and usually on the intake or exhaust side, I cant remember which.) My situation was different from yours i.e. higher compression and different pistons, but I just want to let you know to be careful and maybe let someone who has been around cars alot listen to it and see if they can hear anything. I dont want you to have to go through what I did.

Thanks guys,

That makes me feel a little better about it. That "pinging" terminology was confusing the hell out of me. Taking it easy is good advice.

Clyde

If you suspect detonation..check your plugs. If it detonates(bad enuff) there will be specs(boogers) of aluminum of the porcelean. Looks like purple pepper