Oversize OD main bearings for 37 21 stud block

Yoyodyne

Yoyodyne

Well-known member
The very last check I made before taking my oh so carefully cleaned tested and prepared 37 block to be bored was to bore gage the mains to be sure I had the correct main caps installed. In the process with the aid of searches here on the Barn I discovered that the main bores are .015" oversize. I understand why, but now I need bearings, or else I have to start the process over with yet another block, this is the 5th block I've cleaned and magnafluxed to get one useable block.


Does anyone here have those bearings for the .015 oversize bores? Or can you direct me to someone who might? My crank is .020 under, but I'd consider any undersize, doing another crank would be faster than finding another block.


I had one knowledgeable Barner tell me that Ford never made a rear main bearing for oversize blocks, is that true? My block has all 3 bores oversize.


I've been pondering how to sleeve the bores to make them work with standard bearings. We have ways, but it seems to be impractical. Anyone ever try it?
 
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I have some oversize in the block rear mains inserts --don't know exact sizes though, can look later today
 
Yoyodyne said:
... or else I have to start the process over with yet another block, this is the 5th block I've cleaned and magnafluxed to get one useable block.
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Be sure to get the block pressure tested, mag doesn't find all of the possible cracks on a flathead block. Better to find a problem before you sink a lot of money into it.
 
JSeery said:
Be sure to get the block pressure tested, mag doesn't find all of the possible cracks on a flathead block. Better to find a problem before you sink a lot of money into it.
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Just finished that with this block. Disassemble, clean, mag, derust, pressure test, etc 5X. I keep finding new ways to find problems.
Where are those new blocks Tod?
 
McMaster -Carr has shim stock sheets in .007 and .008 thicknesses with a half thou tolerance spec. About 16 bucks a sheet. I'd be tempted to cut some shims and measure the bores with bearing inserts installed. The bearing crush will keep it in place,no problem.



Terry
 
Bob C said:
I saw that in the parts book. They show front and center but no rear.
I think it showed .010 and .030 with .015 OS for rear.
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I see. He wasn't specific, just said Ford didn't make them. I asked for other sizes, got no answer so I took that as no rear bearings of any size made.
 
The rear main .015" os in block, .020 on journal is #68-6331 Z However, the length between flanges in block is .010 us. total length thrust to thrust is std. Check the width of your blocks flanges.
 
The block is 2.083" I have a rear cap from a junk block that measures 2.090" Is the 2.090 standard?
 
if you can't find .020 bearings, 68 6331 AA is .030 on crankshaft, .015 os and again .010 shorter @ flange
 
Thanks very much for that Brian. Looks like neither length is correct here. The length issues I can deal with, we have ways to machine it and I can even handscrape if necessary. Putting material on is tougher, but a spacer or shim on the length would not be fatal.
 
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