The Stovebolt Site Forums The Shop Area Engine Shop Bearing Clearance, plastigage & Shims

Here is an up date. Today I installed the crankshaft.

The block and crank have been back from the local machine shop for two weeks now. I knew they would be stored in my unheated Michigan garage for a while so I sprayed all the internal and machined surfaces with WD40 and put a plastic bag over everything. I started by cleaning the oil off of the crank main journals, block half-rounds and the main bearing caps. Next I placed the block halves of each bearing insert in place making sure they were the ones with the oil hole and the locating bump on the back side. Then I set the crank into the block on the new bearings being careful not to move or damage the bearings (Not all that easy, the thing is very heavy).

After assembling the other half of each bearing into its respective cap I set each cap in place and tightened then one at a time to insure that each would lock the crank from turning. Next all the caps were removed. Then starting with the rear cap I inserted a home-made 0.003’’ shim on each side, placed a piece of 0.001’’ to 0.003’’green plastigage across the top of the bearing and tightened the bearing cap bolts in 10 ft-lb increments to 100 ft-lb. After carefully removing the cap I checked the crushed plastigage with the scale on the package and found the bearing clearance to be 0.0015’’. I was lucky again on the #3 main, it was also 0.0015’’ with 0.003’’ shims on the first try. The #2 main took 3 tries and ended up at 0.0015’’ with a pair of 0.002’’ shims on each side. The front main took two tries and ended up with 0.002’’ shims on each side for 0.0015’’ clearance.

I then removed all the caps and the crank and installed the rear main seal. One more cleaning of the crank journals and bearings then I coated both with STP (recommended by the machine shop as a great assembly lube). Finally I reassembled everything and torqued all the bolts to 105 ft-lb. Now came the critical moment when I attempted to rotate the crankshaft. It took 40 ft-lb to start it the first time and around 15 ft-lb to keep it turning.

The whole process, including making the shims, took about 6 hours. I’m happy.