Technical > Matt Shaff's Engine Shop

Main Bearing Issues

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msundstrom:
These main bearings came out of my 467 BBC, injected, methanol, FED at 8.20's / powerglide. #3 and #4 sets came out of same rotating assembly as #1 did but #1 (1 pass) was in a 4 bolt block. #3/#4( 3 passes/4 passes) were in a previous 2 bolt block. Main bearing clearance was .0035". Rod bearing were good. The GM steel crank came out of a running engine and the bearings were very good. I used different rods, pistons, etc and had the assembly balanced. Balanced wrong??

masracingtd1167:
You have a very bad problem there and you better start at square one ! Your post is kind of confusing . You have 3 rear main's there and they are all bad . First place I would start is the block . Have the line bore ckecked . The next thing I would do is make shure it is getting oil to the mains . Make shure there are no galley plugs missing . Next check that crank for straightness and out of round . you seem worried about the balance is this a new rotator . Your clearence at .0035 should be fine but make shure you check every one . One more thing I just thought of . How much timming in motor ? If Matt reads this he might have some good suggestions too . Keep us posted with your proggress . Bill

cdafoe:
Mark:  First, I'd have that crank checked by a reputable crank specialist for straightness. Second i would check the blocks main line.  I know some good machinists in the Kent area if you need one.

Chris

LZ:
M
Seems to me for what its worth you have more then one thing going on there. :-\
I know Matt will jump on but just a bit of info for you in meantime.
Mahle has a good page.
http://catalog.mahleclevite.com/bearing/

Good luck
Luke

msundstrom:
My original thought was the block. The first block was a 2 bolt block with main studs and filled, This last set of bearings (#1)is with the rotating assembly in a 4 bolts block with main studs and filled. The upper 2(#3&#4) were from a 2 bolt block. If it was oiling I would think the rod bearings should show damage? Rod bearing clearance is .003". I have two of the engines, they are almost identical short blocks with the exception of crank brands and the other has had no issues. Both were balanced by the same place. This engine had 34' timing with a fat tuneup.
Thanks

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