Minimum Bearing clearance?
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From: Warrenton, Mo
Minimum Bearing clearance?
While building my 289 I discoved the first and second rod bearings, and first main bearing had become contaminated during assembly somehow and had scratched the bearings. I purchaced a new set of Mahle bearings the same .010 oversize as the Clevites I had before, but now the clearance on the rod bearings is much tighter. It was at .035 with the clevites and now is at .015 with the Mahles of the same size. Is this to tight? I really dont want to buy another set, I seemed to be jinxed here.
Hotshot
Joined: May 2004
Posts: 12,170
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From: The hills of No. Calif.
Stock clearance specs are .0015-.0025. .0015 is a little on the tight side, would give good oil pressure on a stock motor. Blueprint specs are a little looser: .0025-.0030. If you're at .015 you're way too loose...and .035 is downright sloppy! Did you forget to add a zero when you posted those numbers?
Last edited by TigerDan; Nov 16, 2005 at 08:13 AM.
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From: Warrenton, Mo
Yes I did, Im sorry, I cant think and type at the same time. So do you think this would be to tight for a high volume(not HP) oil pump, I have read on here that it is not recomended.
Hotshot
Joined: May 2004
Posts: 12,170
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From: The hills of No. Calif.
Don't feel bad. I can't think and talk at the same time, which leads to chronic foot-in-mouth syndrome!
Yes, I think it's a bit tight. I'd be happier seeing about another thou or so of clearance there. Interesting that a change in bearings tightened it up that much. I'd mic the bearings themselves and then check the old Clevites, see if you can read an actual difference in bearing thickness. If so, maybe go back to Clevites or else you need to have the rods resized, a major PITA at this point. I've heard of old-timers taking material off the back of the bearings to gain clearance, but that seems a bit too old-school to me. Hard to take material off evenly. Might as well just make some leather bearings for it if you're gonna go that route!
Yes, I think it's a bit tight. I'd be happier seeing about another thou or so of clearance there. Interesting that a change in bearings tightened it up that much. I'd mic the bearings themselves and then check the old Clevites, see if you can read an actual difference in bearing thickness. If so, maybe go back to Clevites or else you need to have the rods resized, a major PITA at this point. I've heard of old-timers taking material off the back of the bearings to gain clearance, but that seems a bit too old-school to me. Hard to take material off evenly. Might as well just make some leather bearings for it if you're gonna go that route!
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