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Old 06-17-2008, 09:05 PM   #1 (permalink)
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Small block chevy main bearing issue (assembly)

I am trying to put a small block chevy 350 back together and the rear main bearing seems to be wrong. It does not fit over the crank. The crank is ground .010 under and the bearings match in this respect. The thrust surfaces of the bearing do not fit into the crank. The old bearing and the new bearing have the same part number stamped in the back 32020-cp. The casting number on the crank is 932442. Measuring across the bearings there was about .020 difference between the old bearing and the new bearing, with the new bearing being the larger of the two, which I am sure is the problem. I took back the first set of bearings thinking it was a defect and the new bearings have the same problem. From what I can tell from the numbers I think this is a 1975 motor. Are there different types of bearings for this? The bearing brand I am using is Federal Mogul. If anyone has any suggestions I would love to hear them.

Thank you,

Josh
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[QUOTE=anvil]
your very informative reply has been noted. I think this is the same type of logic you used to draw your conclusion.

Place banana in your ear.
Observe that there is no alligators around.
Conclude bananas placed in ears keep aligators away.

[/QUOTE]
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Old 06-17-2008, 09:15 PM   #2 (permalink)
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Quote:
Originally Posted by Al Kaholick View Post
I am trying to put a small block chevy 350 back together and the rear main bearing seems to be wrong. It does not fit over the crank. The crank is ground .010 under and the bearings match in this respect. The thrust surfaces of the bearing do not fit into the crank. The old bearing and the new bearing have the same part number stamped in the back 32020-cp. The casting number on the crank is 932442. Measuring across the bearings there was about .020 difference between the old bearing and the new bearing, with the new bearing being the larger of the two, which I am sure is the problem. I took back the first set of bearings thinking it was a defect and the new bearings have the same problem. From what I can tell from the numbers I think this is a 1975 motor. Are there different types of bearings for this? The bearing brand I am using is Federal Mogul. If anyone has any suggestions I would love to hear them.

Thank you,

Josh
I'm an automotive machinist by trade. The bearings you have are for a .020" oversized thrust. You either need to return those bearings for a standard thrust bearing set or have the crank thrust area opened up to fit those bearings. I would recommend swapping the bearings. Those bearings were made so that instead of having to weld up a bad thrust surface on a crank it could just be opened up .020" and run that bearing set.

Last edited by 4X4HIGH; 06-17-2008 at 09:15 PM.
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Old 06-17-2008, 09:31 PM   #3 (permalink)
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Quote:
Originally Posted by 4X4HIGH View Post
I'm an automotive machinist by trade. The bearings you have are for a .020" oversized thrust. You either need to return those bearings for a standard thrust bearing set or have the crank thrust area opened up to fit those bearings. I would recommend swapping the bearings. Those bearings were made so that instead of having to weld up a bad thrust surface on a crank it could just be opened up .020" and run that bearing set.
This makes sense, is machining the thrust usually done when machining the crank? The overall width of the bearing in millimeters since I dont know how to read my calipers in inches is 44.1 on the new one and 43.6 on the old one. Do they make bearings with what I need?
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[QUOTE=anvil]
your very informative reply has been noted. I think this is the same type of logic you used to draw your conclusion.

Place banana in your ear.
Observe that there is no alligators around.
Conclude bananas placed in ears keep aligators away.

[/QUOTE]
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Old 06-20-2008, 05:14 PM   #4 (permalink)
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Everything went together perfectly with the new bearings with a standard thrust surface. Thank you for the help.
__________________
[QUOTE=anvil]
your very informative reply has been noted. I think this is the same type of logic you used to draw your conclusion.

Place banana in your ear.
Observe that there is no alligators around.
Conclude bananas placed in ears keep aligators away.

[/QUOTE]
Al Kaholick is offline   Reply With Quote
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