Shims for Rod Bearings

johnr9q@yahoo.com

johnr9q@yahoo.com

Senior Member
If I order new Rod bearing shims they are .005 thick, also the ones in my car are .005 thick. I need to get the clearance down to between .001 and .0015. How can I do that when the shims are so thick?
 
From Snyder's shim page...

Made from laminated shim stock. Two shims for rear main, and four for center and front main bearings. A-6340/46 is .032" thick. B-6340/46 is .016" thick. Laminations are .002" thick. U.S.A.
Click to expand...
And

A set of 8 laminated shims for all four rods. Just peel off a layer for adjustment. .030 thick. U.S.A.
Click to expand...
Joe K
 
I've used the brass laminated shims that are now available. They come as a "stack" and are a bit challenging to peel apart. I used a single-edged razor blade to get between the laminations. You need good light and good eyesight for this. Use a caliper or micrometer to measure how many you have peeled off. Maybe enlist the grandkids... IIRC they are about 0.003" thick each.
 
If you peel off one layer on one side of the cap you will half the change in clearance. So peeling off 0.003 on one side will reduce the clearance by 0.0015. Alternate sides.
 
The babbitt bearings should have been reamed to size with shim packs already installed. Thus to adjust the bearing clearance, you remove shims.
 
The bearing is only concentric after it's cut to size. Removing shim stock will decrease clearance but it doesn't help with concentricity. The center main always wears more than the ends so it eventualy has excess pressure on one side of the bearing. This just makes it wear faster. It was never the best way to do things but it worked to get it by a bit longer till the bearings could be repoured. Con rods could soldier on longer but not by much.
 
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