Crank end play tricks ?
 

Hey All,

I started pre-assembly of my 428 yesterday, I started off with checking the main bearing clearances, all checked out at .002 ... then i lubed the bearings, torqued the crank starting with main cap 3,2,4,1,5 all to 100 ft/lbs and then cap 5 to 120 ft/lbs as instructed. My problem is this, I have zero crank end play. I set up the dial gauge on the crank centerline, zeroed it out, moved the crank in both directions. It would move .002 or so, but after I let off pressure it would settle back to 0.

Is there something that I missed, a trick for getting everything settled properly ? Or should i take the thrust bearing out and clearance it a bit to allow some movement?

Thanks !

Remove cap 4 , remove that bearing and with a caliper measure what you have for cheek to cheek distance on the crank , and then measure the width of that half of the thrust bearing, what do you got?

Loosen the thrust bearing cap, SMACK the crankshaft to the rear with a bigass deadblow or other cushioned hammer.

Then SMACK the crankshaft forward, torque the cap, see what the end-clearance is.

If half of the thrust main is slid forward, and half of the thrust main is slid rearward, there may be little or no clearance overall. When both pieces are slid forward, you'd likely have proper clearance, AND the thrust bearing is in the better position for accepting clutch or torque-converter thrust.

If that doesn't work, remove the thrust cap entirely, re-check end-play. I had an Oldsmobile with too-little end play, the machinist that cut the caps before the align hone got one tilted. The cap-side bearing wasn't square to the crank.

If you used a thick assembly lube on the faces of the thrust bearing that will take up clearance. Remove the crank, clean off the thrust bearing and check the end play dry. Like others have said, make sure both halves of the thrust bearing are aligned before torquing.

My experience shows the tilted #4 Main Cap reveals itself after about 30 ft-lb. Thick Studs can frustrate. Stay with Factory Bolts if needing a remedy.

On a Pontiac, the dowel pins really are the locating components for the caps. However, loosening the #4 cap and bonking the crank forward and rearward may give you a little clearance. Chances are, if the block was line honed, they ground a slight tilt into the cap. It's very common. I use layout dye and make a series of very light scratch cuts on the cap parting surface and shim the cap as necessary to make absolutely sure the cap is square in the grinder. It's tedious. If nothing else works for you, you can sand the front side of the thrust bearing on a surface plate with wet/dry paper and oil. I start with 280, then 320 and finish with 400 grit. When you can get an honest .003" minimum "free movement" you are done. Not a big deal. Good luck.

Does the crank spin freely when rotating it with your hand?

Remove the cap and put just the bearing in place if you can.
If so then the issue is something with how the cap is positioning the bearing.

Thanks! this is what I was looking for. I'm going to try it tonight.


The lube I used was like syrup, so I'll check that too. Thanks!

Yes, no binding or spots that it's hard to turn.

Just want to clarify that loosening #4 and whacking the crank to the back and then forward really isn't to square up the cap but to simply set the bearing halves in better alignment with each other. Even though it feels like the bearings are an interference fit when slid on, it's surprising how two or three thousandths can be found.

^^^^ BFH all the way..then final torque. I found the "extra .002" I was looking for during my assembly.

I once pulled apart a SBC that had a trashed thrust bearing and trashed thrust surfaces on the crank. The engine had not been apart before. When I went to reassemble the engine with a different crank, the end play went to zero when the cap was tightened. I checked the side clearance between the thrust surface of the loose bearing and the crank with a feeler gauge and it looked perfect. I tried the whack it back and forth technique to no avail. It still tightened up when the cap bolts were torqued.

On further examination, I noticed that the corner where the thrust sides of cap and block met the main bearing surface was sharp. There was no chamfer from the factory. When the cap was tightened, that sharp corner pushed into the inner radius of the bearing and flared out the thrust surfaces of the bearing against the crank thrust surfaces. This factory defect had trashed a nice forged factory crankshaft.

I chanfered the corners by hand with a die grinder and all was well from there.

I've never seen that done ,wacking the crank. Hmm interesting. 'Sanding' the bearings I've never had to do that. Thanks guys for the 'ideas'.

you can also use a long flat blade screwdriver to pry the crank fore and aft to set the thrust bearing.

either method main thing is not to use to much force to bend crack or mar anything just enough force to get the thrust faces on the same plane

^^^yup and as I learned assembly lube is ....FAT!!!!! oil doesn't squeeze very well and grease DOES NOT squeeze at all! When you have 2 FLAT surfaces grease is "extra"....

I'll keep that in mind while I'm trying things out. Thanks

I did use the gooeyest of assembly lubes LOL. I'll try cleaning it off of the thrust surfaces while I'm in there.

Just setting the alignment, got it