Piston / Valve clearance on a /6 |
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Piston / Valve clearance on a /6 |
ahdoman |
Sep 15 2008, 11:51 PM
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#1
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It's phonetic...Ah-D-O-Man (Audioman) Group: Members Posts: 667 Joined: 7-November 05 From: Santa Clarita, Ca. Member No.: 5,084 Region Association: Southern California |
I've been reading Wayne Dempsey's "rebuilding your 911 engine 1965 - 1989" book. Really good stuff! However, I do have one question in relation to piston & valve clearance; If I understand him correctly you add the copper shims at the bottom of the barrel to adjust deck height clearance. Does adding copper shims also lower the compression ratio as well? If so, is there any ratio formula for shim thikness to ratio decline? Then if you achieve proper deck height would piston / valve clearance only change if a head was machined?
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smdubovsky |
Sep 17 2008, 08:59 AM
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#2
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Member Group: Members Posts: 331 Joined: 27-September 04 From: Silver Spring, MD Member No.: 2,837 Region Association: MidAtlantic Region |
Krusty is spot on. Though I'll add a little bit more. You don't shim the cyl height to correct for valve to piston clearance. Thats done w/ proper cams and/or valve relief cutouts in the pistons. The deck height takes care of the piston to HEAD clearance. Almost always out at the very edge. W/o enough deck height the pistons will hit the heads.
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