building a 400ex with a diffrent piston then i normally use. it has a hell-a dome on it. i mean biggg. my question is at TDC is there a chance of it smacking my spark plug? and if so, what can i do to fix it? thanks

 

If you have conserns, consult the piston manufacturer.
Normally if there are no valve reliefs milled into the dome, a spark plug issue should not exist.
My thoughts on the piston are if the head has been shaved. There I will cc the head before and after shaving. There are also formulas out there that us engine builders use for optimum compression for the engine in question. Some times milling from the top side of domes are needed. A few other things I watch with the added dome is the difference in weight of the rotating mass with the extra dome. It might throw the crank out of balance. Also, if the intake valve will chase and hit the piston as it opens. Clearance is needed for higher RPM operation in this area also.
If no shaving of the head was done and the manufacturer of said piston has no warnings in the installation notes for a stock engine, there should be no issues.
Just to be safe, clay the piston installed and check clearance before starting the engine up.

----- Gimpster -----

 

sounds good. im using a je 426 13:1. there is a tip at the dome that looks like it may hit the plug. well have to see. thanx