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127" Ultima Piston Ring Gap?

09GLDR

Member
Ok all you techs out there, I have been pouring all over the internet looking for the proper piston ring gap size for a 127" Ultima motor that a buddy of mine is putting together. So I thought I would throw it out here and see if anyone knows. Thank you for any feed back!
 
I am just pulling an answer out of thin air because I am no engine builder but I would say the person to ask is the cylinder manufacture. What the cylinder is made from along with the coefficient of expansion rates would dictate the ring gap to me. Since we are air cooled, temp swings are great.

I am sure your looking for peak power so you don't want it greater than what it needs to be.
 
I would use std gap if the builder cannot be contacted. Too much gap ring and cylinder damage, too little gap less compression and oil control JMO and I would check all of the rings, filing rings aint no fun
 
.004 for every inc of cylinder bore is a rule of thumb:s
 
.004-.005" per inch of bore, and if running a cast-iron cylinder, .0055-.006" is not out the qusetion.
If fitted too snug, they can/will butt togather, and the can/will break.
THAT is NOT what you want.
Scott
 
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