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Old 02-02-2010, 09:58 AM   #1
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Default piston clearance issues over size valves...

Are there any forscene piston valve clearance issues doing 1mm over size valves with my wiseco 60 over pistons. When my machine guy did my block he mentioned something about keeping valve size stock when I built my head. I couldn't see there being a problem, but he's the pro so I have to question my self before ordering valves. The only solution to this problem if one really even exsists, would be running a thinker head gasket? Any help<my knowledge.
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Old 02-02-2010, 10:42 AM   #2
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Are there any forscene piston valve clearance issues doing 1mm over size valves with my wiseco 60 over pistons. When my machine guy did my block he mentioned something about keeping valve size stock when I built my head. I couldn't see there being a problem, but he's the pro so I have to question my self before ordering valves. The only solution to this problem if one really even exsists, would be running a thinker head gasket? Any help<my knowledge.
You really need to check piston-to-valve clearance if you are going to run oversize valves with non-stock pistons. Mock-up the engine with a used (already compressed) head gasket and put modeling clay over the piston valve reliefs on at least one piston. Rotate the engine over to get full valve opening (need to use solid lifters or modified stock hydraulics) and then dis-assemble and mic the clay thickness on the piston where the valves have compressed it.

The best way to get more PTV is to modify the piston valve reliefs; using a thicker head gasket or lowering the piston deck height is going to reduce quench and potentially increase your chances of detonation.
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Old 02-02-2010, 10:46 AM   #3
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Fastcolt, just curious what your CR is? I guess I should think about the same thing on my build, thanks for bringing it up.
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Old 02-02-2010, 10:57 AM   #4
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Fastcolt, just curious what your CR is? I guess I should think about the same thing on my build, thanks for bringing it up.
CR? My credit rating? LOL Compression Ratio im guessing? I think my wisecos are 8.5:1. I know they'er lower then stock for boost.
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Old 02-02-2010, 06:02 PM   #5
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Seems like compression ratio is something you want to be absolutely certain about.
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