Engine builders, piston Fitment

[rumblefish360]

Hey fellas, the piston in question is a KB Hyper-U (191).

Piston measures 4.00 (4.0025/30 ish) area.
How much clearance does the KB Hyper-U need.

Similar question for a forged and regular cast slug.

 

[moper]

The instructions are available on the KB site. Clearance depends on bore size, the piston material, and the use, and it's set by the final bore size.
Usually KB hypers are .0015-.002 for light use. .0025 for higher performance. You can run more if you have to but they might get noisey.
Forged usually want more but again, it depends on the material. anywhere from .0025-.004+.
Cast factory are a little tighter than forged, not as tight as hypers.

 

[rumblefish360]

Thanks Moper, this page then---> [ame]https://www.uempistons.com/installation_instructions/kb_installation.pdf[/ame]

4.000 - 4.100 bore sizes get a .0015 - .0020 for naturally aspirated engine.

 

[moper]

Yeah. If you notice, the more heat they're likely to get, the more clearance... So if this is going to work hard (towing, racing, road racing, etc) then you may want more.

 

[rumblefish360]

Yes, I did notice father down the specs increased some. The intended useage would require some more clearance.