I am building a lq4 based 408 and recently got the main bearing clearance where I would like using a set of speed pro 152m1x bearings. After getting the bearing clearance set I moved in to setting thrust clearance and found that if I measure the thrust without the #3 main cap I get about .007” if I torque the #3 main cap down the clearance drops to .004” and I noticed that a can slide a .002” feeler gauge into the top of the bearing but not the bottom towards the front and into the bottom but not the top towards the rear. It appears like the main caps are not aligned. I have done the thrust bearing setting procedure probably 20 times with the same result every time. What do I do in this situation? Could I polish the difference off one side of the upper shell and of the opposite side of the lower?

 

Specs call for crankshaft end play range at .0015-.0078.

i would call it good and not worry about it if it is truly .004

 

I’m just worried about the fact that the halves of the thrust bearing aren’t lined up. There’s about a 2 thou difference between them

 

Good observation. You are correct that it’s an issue and needs to be correct.

Since the thrust in the LS tends to be whimpy, you most certainly at least want the thrust side halves aligned.

I would measure both halves across the thrust faces and see if they are the same.
I would then install in the block and cap and remeasure.
This will get you numbers to ponder.

Next I would put the cap on, bolts just finger tight and see if you can tap the cap rearward and align the two sides. No crank in just yet. Then tighten the bolts and see if it stays there.

You may end up sanding that top shell which is quite easy with a flat plate, 600 grit and WD40.
If you were able to align the two as mentioned above, sand the forward face.

I’ve not had a lot of luck whacking the crank back and forth to set the thrust. The cap simply tips one way or the other and the clearance changes when you tighten the bolts.

I think you will figure it out from here. 😊

Clearly I’m not in the “send it” crowd.

Ron

 

what method do you use for setting the thrust bearing. I have put the cap in without the crank and tapped it around with a hammer and I can get them almost perfectly even but as soon as I put the crank in I can’t get it to line up again. I agree it seems like it just makes the cap tip one way or another. I have measured the shell thickness of each half of the thrust bearing and they are the same top to bottom.

 

In the precision world, .002 is the maximum allowance but, within tolerance.

If it is eating at you. Do some light sanding in a figure 8 pattern as suggested by another member.

 

If it's out when you torque it, it may be the mating surface of either the cap and/or the block saddle are tapered.
Also, the mating ends of the brg halves may be whacko.
I'd put the brg in, torque it down w/o the crank. What does the parting line look like?
Any dimensional variation from the ft of the brg to the rear when doing this?

 

I have put it the bearing into the block without the crank. Without the crank I can tap the base of the cap and get it lined up almost perfect and it will stay that way after I torque it down. If I do the thrust bearing setting procedure it just seems like it makes the cap tip back and forth.

 

Thank you so much for the suggestion.

 

Look guys, it’s another bot today…

 

All good now?

 

Aaaaand... another one...