Main bearing shims

J Franklin

J Franklin

Well-known member
I need to buy some main bearing shims for my 1934 engine but can't seem to find a supplier. Are they available or will i need to cut my own.
 
J Franklin said:
I had thought about that but wondered if I would be building a V-8 battery with the dissimilar metals.
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Steel shim stock is available if you want to overthink this dis-similar metals stuff. Keep things simple and follow Walt's advice, but, keep in mind he has only been building flatheads for less than 50 years.
John
 
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Thank you guys for the response, the guy that rebult this engine liked to set up the babbet bearings fairly tight. I pulled the engine once to plastigage the mains and found them at .001 and thought that was ok as he did my model A engine similarly, and after I was able to get it running it has been a nice running engine. I pulled some caps on the model A after a few thousand miles and all looked great, and the bearings were at .0015. so I thought the V-8 would be similar. But I cannot turn it by hand at all, even after dragging it around with the plugs out for a few blocks. To get the engine to turn while dragging it I had to step on the starter and let the clutch out at the same time it was being pulled. All the rods were just fine, it was just the mains. When I get it running I will restore the sheet metal.
 
Chilton's '40-'56 Manual has a good description regarding shimming mains, including use of aluminum foil. Crank journal(s) may be out-of-round, shims too tight or shims incorrectly installed if you can't turn it by hand.
 
I am not too confident in the longevity of aluminum foil shims in that kind of environment. Most well stocked hobby shops sell brass shim stock in a variety of thicknesses. I found a packet of shim stock with several sheets each of 0.001, 0.002, and 0.005 inch thickness and that is what I have used. Harbor Freight sells a set of gasket hole punches for a modest price and you can scissor out the rest of it. Old school but it works!
 
At .001 it should turn, the specs I found say .0005 to .0025----more likely the crankshaft is not to specs(out of round,or taper), or the linebore is not in line
 
The old timers used Prussian blue and scraped the highs with a bearing scraper.Not a difficult job and is the time proven method.Phil
 
It will turn with a bar or when pulled just not with a hand crank. the crankshaft was ground when it was rebuilt. I have never heard of setting mains on babbit at .0005. I will add a thousandth and it will be fine. The rebuilder did my model A engine and it really runs well but was tight as well though it had 4 less cylinders to drag. I had to drag it around a mile or so and then started it on a hill rolling and starter+let out the clutch. It started and I let it run about a minute then started it for another minute or so a few more times before I drove it a bit. Checking the babbit after a few thousand miles all looked great. This rebuilder balanced things on both engines to 1/2 gram. I think he just had his own ideas about things.
 
A dial indicator set up on the center main bearing with the end bearing caps on and tightened should give you an idea about whether or not there is any bend in the crankshaft. Give a few rotations and look for runout.
 
off topic...Removing the shims didn't help so I ground the rod caps on a 1948 brand X to quiet it down before selling it. Worked fine but needed a 12v jumper to crank it over the first time. The buyer told me he was going to put in a Jimmy, so i didn't lose any sleep over it.
 
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