JFOLM

iTrader: (8)

You would rather take material away from where the spark plug is held than to flycut a piston?

Gadgetized

iTrader: (9)

Where are you going to take material away on the head with a file to give more clearance? .081 seems a bit far to me. I have ran .035 without a problem. If I were worried I would run a spark plug indexer to move the plug away.

custm2500

iTrader: (10)

I had seen .081 on ls1tech. I have more then that with my valves so I am great on that aspect.

Gadgetized:If I clearanced the head I would file a few thousands from the area that is contacting the piston.

JFOLM: I am trying to decide. Seems to me that a tiny shave to the head would be better then a tiny shave to the piston. The head is easily replaceable if it were to crack and they are 317s that to directly replace costs me around $250 for a pair. Personally I like the idea of that much better then cutting into the piston that is much harder to replace and significantly more expensive.

If the gasket alone gets me so they don't touch I will be taking .05 at most off the extra large knot in the head and that seems plenty safe to me. You can't tell all that well in the picture but there is a lot of meat between the contact point and the spark plug thread. Maybe I am wrong, and that is why I come on these forums for advice, but I don't think a few thousands is going to cause any issue to the spark plug boss.

swift700

iTrader: (3)

Take off the material where you need to take it off, whether it's in the chamber or on the piston, or both. BTW, what kind of pistons are those? Never saw any like that before.

custm2500

iTrader: (10)

Dimond nitrous pistons.

Atomic

iTrader: (42)

This is an interesting topic...

I dont see what shaving material off the head will do....the spark plug depth is determined by the threads, not the area in the chamber. I agree with using spark plug index rings if you need more clearance.

splinter

Between .035-.045 is generally considered the safe minimum for final deck (crown-to-chamber) clearances.
Nevertheless, a quick pass with the grinder might be worth the peace of mind.

Valves require additional space since they’re moving and the piston is trying to smack ‘em during float/bounce!

dmelvin

iTrader: (8)

Atomic:

I don't think he's hitting the actual plug, I think he's hitting the area around the plug.

custm2500

iTrader: (10)

Correct, I am hitting just the head that is surrounding the plug. The ground strap is at it's most dangerous position on one of the cylenders and they don't hit the plug.

Atomic

iTrader: (42)

Oh, my bad, I thought you meant you were hitting the ground strap. In that case I dont see a problem with a little grinding on that bump.