[bullheimer]

I read some posts where you have to use a larger gap with hyper utectic pistons. My pistons came with no directions for ring install. (sealed power hypers). My machinist, who I won't question says that the bigger gaps were for the Keith Black hypers because the ring grooves were too high up and caused excessive heat, whereas the ones I have they are in the normal place so ring gap is normal, per the Hastings directions that's .004" per inch of bore so for a 4" bore .016". Should I go with it? Can someone back up the std gap on these? thx

[DoubleVision]

sealed power hypers don`t require the rings be gapped.
Smokey Yunick was one of the first to experiment with pistons with higher placed ring lands, he discovered as they went up the gaps had to be wider due to more heat. the engineers told him this was impossible because their text books said .340 inch below was the limit, he moved it as high up as .150 with no problems. He thought there was much to be gained by the rings being higher up on the piston, it would eliminate more dead space and clean up the combustion process and etc.

[engineguy]

Bullheimer,
Your machinist is correct, normal gap is right for the Sealed Power hypers, because the top ring is not as high on the piston. The ring gap does depend somewhat upon the type of rings you are using in the top groove. .004" per inch of bore is OK with ductile iron or steel base material, but I would go a little wider if the top ring is cast grey iron. Most performance ring sets (Speed Pro, Clevite High Performance, Childs & Albert, JE, Cp, etc.) do use a ductile moly top ring. Some of the "less expensive" performance rings sets do use cast grey iron top ring with moly facing.

[machine shop tom]

Double V is correct about the Sealed Power/Speed Pro ring end gap recommendation. On these pistons, I use the gaps as recommended by the ring manufacturer. It doesn't hurt to use the high end of the limits. Too little gap is far worse than too much.

[F-1Rodder]

Bullheirmer: right or wrong, the advice you got was the same as I got, built and drive. It hasn't broken yet and may be the only thing that hasn't broken.

[hotrod_death_toll]

Wow brutal!! Go by the ring specs on the high end if you're worried.