rithsleeper

Finally think I have a consistent ignition with genuine gm parts but still not sure. However when I was finding TDC with a piston stop the piston didn't stop because of the angled plug. It just bent it.

I did a quick dry compression test to see if I had bent the valve since dumbass me didn't remove the rocker. Things looked good. I got a bore scope from harbor freight and it was just a bit too big to fit into the spark plug hole but I could still clearly see a mark on the piston reflecting. I'd say it was maybe 1/8 long if even that.

My thought is it is nothing to worry about but I also was thinking could this cut end up gathering carbon build up and causing detonation when it is on the track?

I will be tracking this engine hard for 30 min sessions in the middle of the summer. Just wanted to know if anyone had previous experience and if it is something to worry about or possibly try to take off the head and try rounding off the edges of the scratch?

1963SS

It depends how much I guess. There is a lot of polishing done to get rid of stuff like that. Anything that can retain heat and "glow" red can cause detonation. The fuel will think it's a spark. I'd certainly try to get it smooth again. Well, not smooth exactly just get the ridges off it and round the edges. You'll be fine.

Brian Felts

YES any nick can create a hot spot that in turn can cause pre ignition in the chamber.



Brian

rithsleeper

Now another question would be how long would it take before it started? Could it happen at idle or would it have to be when the car was turinging a higher rpm. I've got a lot of noise that I think is just valves and a header leak but until I fix them a knock is suspect....

1963SS

Picture a glowing ember on top of your piston. As the piston starts down on the intake stroke, the injector starts to feed fuel into the air. The fuel could ignite anytime it wanted bust most typically when under compression with the proper A/F ratio. Yes, it could happen at idle but more likely at a higher RPM. In any event I'd take car of the nick first and then see what's happening with the knock if it's still present.

DanielRicany

Not to hijack but I'm curious to know if the same rule applies to nicks on the head?

Brian Felts

I don't think it would happen as quickly as on a piston but in theory yes. Notice there is never a sharp edge in any combustion chamber.


B

cv67

I wouldnt worry about it

rithsleeper

I'll prob pull it to be safe but that is an annoying amount of work. With all the money into this engine at least it will be better safe than sorry. I guess I can varify my initial tdc also...

383vett

You're not going to get detonation at idle.

jake corvette

rithsleeper - -

You do not have a problem. Like none. Do not worry about this minor scratch. Drive your car - this means nothing.

If this blemish was a problem then it would have shown up in every engine which has valve reliefs in the piston top. And some valve reliefs do have some very sharp edges - some of which are very long and very deep and there are hundreds of million of pistons which have valve reliefs.

Drive your car - this is a non-issue. Combustion by-products - carbon - is a much greater problem than your minor scratch will ever be. This minor scratch will not cause any detonation at all.

Might not be too wise to open your engine and in so doing cause more problems than what you had to begin with.

Churchkey

If your **** + a NASA inspector put a new slug in the hole.

I agree with post 8 & 11 = run that sucker, no worries.