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PCA Member since 1988
Join Date: Feb 2018
Location: SW Washington State
Posts: 4,578
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Ring land clearance is the space between the ring and the land. You typically measure it by inserting a feeler gauge between the ring and the lands and checking all around to make sure it's even and within spec. Porsche calls this the "piston ring height clearance." From the Tech Specs, for SC engines it should be:
Comp ring 1: .070mm to .102mm, wear limit: .20mm
Comp ring : .040mm to .072mm, wear limit: .20mm
Oil ring 3: .020mm to .052mm, wear limit .10mm
If there's any carbon down in the grooves on the piston, clean them out very carefully. You do not to want to gouge the tops and bottoms of the ring lands.
To borrow a quote from Smokey Yunik (RIP, famous NASCAR mechanic and designer), the seal between the rings and bottoms of the lands is the most important seal in the engine.
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1973.5 911T with RoW 1980 SC CIS stroked to 3.2, 10:1 Mahle Sport p/c's, TBC exhaust ports, M1 cams, SSI's. RSR bushings & adj spring plates, Koni Sports, 21/26mm T-bars, stock swaybars, 16x7 Fuchs w Michelin Pilot Sport A/S 3+, 205/55-16 at all 4 corners.
Cars are for driving. If you want art, get something you can hang on the wall!
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