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Connecting rod clearany
i have recently finished a rebuild on a 455. It is now 40 over also with roller cams and roller rockers. Ran the engine approximately 8 hours on the stand and chances the oil two times during that initial break in. Then changed it again- ran for two more hours then installed in the boat and ran for 8 hours on the lake at various speeds. Brought the bought home, changed the oil and am finding copper colored material in the oil. Question.... what is the proper bearing clearance for this engine? The machinists set me up with .0015”. I’m concerned that didn’t allow enough oil film and we trashed the bearings. Any thoughts out there? woodchop |
I think you posted in the wrong area. But since I am already here, I'll offer my 2 cents. The general rule of thumb is .001 clearance for each inch of bearing diameter. Then performance engine builders usually add a bit more clearance to increase oil flow and bearing cooling. So .0015 is a bit tight. Most builders would make it more like .0025- .003. However, if assembled and run carefully with proper oil and cooling, it will live with .0015. What other signs of failure are you having? Has the oil pressure changed? Is the engine making noise? Is it heating up the oil?
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i am running .0028 on rods and .0035 on mains
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Originally Posted by woodchop
(Post 4696547)
i have recently finished a rebuild on a 455. It is now 40 over also with roller cams and roller rockers. Ran the engine approximately 8 hours on the stand and chances the oil two times during that initial break in. Then changed it again- ran for two more hours then installed in the boat and ran for 8 hours on the lake at various speeds. Brought the bought home, changed the oil and am finding copper colored material in the oil. Question.... what is the proper bearing clearance for this engine? The machinists set me up with .0015”. I’m concerned that didn’t allow enough oil film and we trashed the bearings. Any thoughts out there? woodchop |
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