robertearl

I am reassembling my sons LT1 I just got back from the machine shop. I was checking the crank bearing clearances when I noticed that the rear thrust bearing faces did not line up. the upper bearing was about .01 of an inch further to the rear on the top bearing than the bottom one. The cap face was flush with the block on the rear. If I tapped the cap forward I could get the thrust bearing surfaces to match up but then the cap face did not line up with the block at the rear. The thrust bearing faces appear to be copper. Do I line up the cap face with the block and let the bearing faces wear down ( assuming I have the minimum of .0002 thrust clearance ) or do I line up the faces of the bearings and fill in the block cap area with sealant when I put on the rear main seal?

Reb

MachinistOne

You use the crank to align the rear surfaces of the two halves of the thrust bearing because that is where the load will be in operation.

Put all your lower bearings in place in the block, apply assembly lube to surfaces of the bearings and thrust flange.

Set crank in place and measure end play with a dial indicator on the snout of the crank. Use a long screwdriver to lightly shift the crank fore and aft to measure how much it moves. Write this number down... for example .008", this is your "block end play" measurement.

Set thrust cap in place with bearing installed and assembly lube on bearing faces. Lightly snug cap bolts.

Now with a rubber mallet first smack the snout of the crank back to the rear of the block to align the thrust bearing faces against the crank, then smack the rear flange of the crank forward to shift the bearings forward in the saddle.

At this point I pry forward on the crank with the screwdriver or a small prybar between a counterweight and the block main webbing to pre-load the bearings forward as you torque that cap to spec.

Measure end play again, it will usually be a thou or two less than your initial measurement. For example .006", this is your "crank end play" measurement.

That is the situation if everything went well...but if you had measured .002" crank end play then you might have a problem with either your procedure, the bearings, or the main cap. If the block was align honed and the main cap was not clipped perfectly square then it will sit crooked on the block and significantly tighten the end play once torqued up.



Unlike the earlier gen 1 SBC, you do not need to seal the cap when you install it, the rear main seal retainer takes care of this for you.

robertearl

Thank you sir.

Reb