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Engine rebuild help (specificatons)
I am currently rebuilding a '84 TType engine. Installed the new crank main bearings, torqued them down, removed one cap at a time to check the main bearing oil clearance w/plastic gage and it measured 0.002" to 0.0022" across the 4 bearings. My Chilton's and Haynes manuals call out 0.0003"-0.0018" for mains (and 0.0005"-0.0026" for rods). I took the bearings back to the NAPA parts dealer and their Clevite 77 bearing manual calls out 0.0005"-0.0034" for mains (and 0.001"-0.0037" for rods). Which specifications are correct? What concerns are there if I was to use the 0.002" to 0.0022" clearance bearings? My goal is to get 100K+ miles out of this rebuild. p.s. I am also installing a high volume oil pump kit.
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#2
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Re: Engine rebuild help (specificatons)
My 1984 GM factory service manual states clearances that match what you quote from your Chilton's manual: Mains = .0003-.0018 Rods = 0.0005-.0026.
Jack Merkel (http://www.merkelengines.com/) writes: "…we recommend main bearing clearance of .0015” - .002” (.0015” preferred) and rod bearing clearance of .0018” - .002” (.0018 preferred)." I'm going with Jack's recommendation on my rebuild since I expect infrequent racing use and mostly street driving.
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Paul Fredricks pfredricks@gnttype.org |
#3
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Re: Engine rebuild help (specificatons)
Thanks for the input- the tighter specification sounds better to me as well! I guess I will have to work this out with the parts dealer.
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#4
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Re: Engine rebuild help (specificatons)
Im also in the middle of a rebuild. I spoke with Jack Merkel personally and he says things have changed since federal mogul now offers 3/4 oil groove main bearings. Also make sure you go with the wider rod bearing. Part # 6-3755APA are 10% wider than stock. The updated clearences if I remember correctly are .0018 to .0022 .002 prefered mains . 0015 to .0022 rods with .0018 stiil being an excellent choice for a hot street engine . All out race motors go with the looser of the specs . Good luck and let me know how things turn out. Doug Conyer 1985 WH1
Last edited by arthdgls; 04-01-2005 at 08:16 PM. |
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