Main bearing and rod instillation on a Model A

[50Trucking]

I knocked out a rod on my A. I have removed the engine and had the crank checked and polished to .20. I purchased the one rod that was knocking and have started reassembly.

I find there is little on the internet that shows or tells how to install and tighten the main bearings. I have been using Les Andrew’s book but not sure if I am doing it right. I started with the center main cap. I removed or added shims until the crank would not turn by hand. I then added 1 shim to each side and used plastiguage and tightened the center cap to 50 pounds. After a couple tries adding or removing shims, I squeezed the plastiguage to 1 thousands. I then cleaned the journal and applied a lubricant and tightened the cap to 80 pounds. The crank would not turn. I was told to add one shim from 1 side and retorque to 80 pounds.

I made an attachment with a socket bolted to the end of the crank so I could check torque. It turns with less than 45 pounds. This bothers me because the plastiguage showed it right at 50 pounds and locked at 80 pounds.

Now that I have added one shim, should I plastiguage again.

Will the 45 pounds be maintained with all caps tightened and the rods installed or should I get shims and torque right on one journal, then loosen and go to the next journel and get it to specs, loosen and so on until all are individually torqued and crank will turn 45 lbs or less and then tighten all rods and mains to specs and then should the crank turn at 45 pounds.

[Jim Brierley]

It takes two .001" shims to add .001" of clearance. I say .0015" is the minimum that you should have, same on the rods. even .002" is not too much. Turn the engine over at least 1 full turn after adjusting each and every bearing. Amount of drag while turning the crank??? The rings are the biggest draw.

[nkaminar]

Use the torque that you intend to install the bearings at to test the clearance. Use assembly lube when you do the final assembly. Use the yellow Timesaver to get the clearance set exactly right. Ideally the crankshaft should turn with very little effort after the final assembly. If the crankshaft does not turn or turns with lots of effort then the bearings are not set correctly. You could have high spots in the bearings so that the Plastigauge will indicate correct clearance but the crankshaft will be hard to turn. The Timesaver will remove the high spots and make the bearing conform to the crankshaft. Make sure the crankshaft is not bent. Put it in the block and fasten the front and rear bearings and if there is a tight spot when you turn the crank it is bent.

[50Trucking]

What is yellow timesaver?

[oldspert]

Originally Posted by 50Trucking

What is yellow timesaver?

^^ this? Never heard of it.

[nkaminar]

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Yellow Timesaver is a fine lapping compound that only laps soft metals, not the steel that the crankshaft is made of. Instructions come with the material.

See https://www.snydersantiqueauto.com/p...d=980308&cat=0