Deck Height and Valve Relief, What would you do? |
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Deck Height and Valve Relief, What would you do? |
BeatNavy |
Mar 4 2019, 06:44 PM
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#1
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Certified Professional Scapegoat Group: Members Posts: 2,924 Joined: 26-February 14 From: Easton, MD Member No.: 17,042 Region Association: MidAtlantic Region |
While I wait (seemingly forever) for back-ordered rocker shims to arrive from aircooled, I keep debating in my head which way to go on deck height on a 2056 rebuild I am doing:
CC volume is 59.8 (calculated by Len Hoffman) Raby 9950 (FI) cam JE Pistons with valve relief Deck height w/o any barrel shims is .032. That gives me a CR of 8.6, assuming the valve relief adds about 2 cc's to CC volume. Adding a .010 shim puts me just shy of 8.4 CR with a deck height of .042. .042 deck height is safer. Pretty sure I wouldn't go .032 deck height with flat tops, but does the valve relief give me enough "safety?" This is my first Type 4 rebuild, so maybe I should go conservative? Am I crazy considering going less than .035? I've done the "clay test" with deck height at .042, and there's no issue there. What would you do? |
VaccaRabite |
Mar 5 2019, 09:48 AM
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#2
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En Garde! Group: Admin Posts: 13,465 Joined: 15-December 03 From: Dallastown, PA Member No.: 1,435 Region Association: MidAtlantic Region |
The old rule of thumb was that .040 was the smallest safe deck height. Tighter then that you needed to measure and be SURE.
Some guys would measure by putting a little lump pf clay/play-doh on the piston and rotating the engine by hand. Then pulling the head off and looking at the clay to see how much room they had after it was squished by the valve. Are you running a head gasket? Zach |
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