Small block thrust bearing cap alignment

Guys, ref 360, thrust bearing cap to block alignment. I have ARP mains studs, without bearings fitted I noticed the surfaces front and rear of the #3 bearing cap to block did not have a slight miss alignment/step, installed the bearing and others in the block and dropped the crank in, measured crank end float at 0.018”, then installed the #3 cap with thrust bearing, re measured crank end float is now 0.001”.. Block has been align bored and prepped however should the #3 main cap have such an offset? I would have thought the front and rear surfaces should have had a smooth transition?

Put the crank in it and snug the caps.. then use
a mallet and hit the crank back and forth a couple
of times then measure your end play and check your
# 3 bearing

Thanks Mr P, yep that’s what I did, the #3 cap will not “float” and settle in as such prior to tightening, what I have now is the upper back side of the thrust bearing doing the work and the lower front side of the bearing doing the work, not full contact, and like I said, with the bearing shell in the block I have 0.018” install the cap snugged down then slightly back the nuts off, tap the crank back and forth, re snug the nuts and have 0.001”, I can add clearance by carefully swiping on a surface plate one side of the bearing shell.
Is it ok to only have one half of the bearing handling thrust?

No. You will wipe the oil off of the surface like a scaper.

That’s what I’m thinking

The studs are most likely larger shank diameter than the original bolts. Open up the holes in the cap. Then when you seat the cap you can move it where it needs to be. Make sure to seat it with cap moved forward.
Doug

Thanks Doug,
I did notice without the crank installed and having the caps installed, the studs on #3 can’t be wound out like the others, i.e, there is binding in the hole of the cap, this I also don’t like.
So if I open up the cap holes on #3 in order to align the cap with the block, thus removing the bearing half offset to prevent wiping oil off like a scraper, I’ll be left with 0.018” end float on the crank, are std diam with oversized thrust available?

Try loosening the nuts up on that main bearing cap only and hitting the front and back of the crank with a hammer on a block of wood to see if you can get more end play with the main cap loose, if so then try barely tightening, 10 to 25 Ft lbs torque or 100 to 250 inch lbs torque, one nut up only and see if it limits the end play or not. If it doesn't then tighten the other nut up the same amount and try again
If it then has no end play after that I would suspect the cap or blocks are not machined square to each other making it impossible to get the proper, .004 to .010, end play needed with new main bearings
I have seen that here locally after having a block aligned honed

Never had this issue on mine. ARP studs didn't create any problems. Bump the crank back and forth to align the bearing halves. Also need to use a large screwdriver or bar to push the crank forward while tightening. .018 is a bunch. Shouldn't have to put the other half in to fix that. Someone would really have to screw up the cap during line boring. Does the cap look square to the bottom surface of the block? I assume the cap is original to the block and putting it on the block correctly?

Put the bearing shell thrust surface on a piece of 240 grit sand paper against a pane of glass. I used my garage window. The last one I did (currently in my 900hp 572") had a surface that was even close to flat. Didn't take to much to bring it around.
Doug

thats how I fixed mine.

Thanks guys, let me measure a few things up, I also have a set of OEM cap bolts, I’ll insert them just for giggles and see what difference that makes and come back with findings

I had a 340 align honed and when the guy ground the thrust cap he didnt cut it at 90 degree to the thrust area so when you would tourque that cap it would pull it over and remove all the clearance, took a bit of work to fix the f up.

Thanks guys, I’ll have a better look on the weekend, I have managed to get more end float by leaving the cap nuts loose and dead blowing the crank but still not right, does anyone know the width of the thrust bearing as new? What they should be?

Just wondering, was this the original cap for the block? if not, it could very well affect that locating. Look at a bunch of caps,and you'll see the holes all over the place in them. ( think like looking at core shift in a part)

Most likely, as mentioned, you will need to ream ( an adjustable blade reamer works fine if you have access) or drill the cap, so that it can properly locate itself.The registers hold the cap in the block and locate it anyhow, the bolts and studs keep it all together. Once you open up the holes, the cap will float, then you can set the thrust with a deadblow hammer. I always start with the crank snout, then back to the flange. Dont be afraid to hit it either, you wont hurt it. You will immediately see the crank spin more freely after you set the thrust from the back.

Ok, small update, so I backed the cap nuts off and deadblowed the crank fire and aft with a little more vigor, now I have 0.005” end float. HOWEVER, what still concerns me is the fact that when I put the bearing halves in the block and installed the crank without caps in place I had 0.018” end float!, now that tells me that the bearing cap is going to take the force of the crank thrust, in my mind I’d rather the block take work load than a cap which could be made walk fore and aft possibly???, it’s a brand new eagle 4340 forged crank, is there oversized thrust bearings????

Did you enlarge the cap holes?
Doug

I would say your good.

No not as of yet, I need to pull the crank out and have a better look at the whole thing this weekend

I have had this before. Machine shop had a chip or burr on grinding table for removing material on cap parting line. I had .009 endplay until snugging bolts and then nothing. Block will need to be re align honed. Take a thrust bearing with you and have them cut the cap parting line with the bearing loaded in cap. That will square it for sure. Bearing will probably not be able to be used as some material will be removed from it as well.

Sure there could be an error cutting the cap. But start simple first. See if the studs are bound up due to interference between the studs and the holes in the cap, 10 minute repair.
Doug

Doug I know they are so will be looking into that for sure

PM'd you crash I would like to hear back from you, I have the same problem with my 360, 17/32 hole is recommended when going to 1/2 stud but not sure if it may break into the bearing tab locator, I run my new out of box arp studs up in a lathe and found the shank of stud to be out of round aswel. I end up sanding the bearing to reach my clearance but have a 0.006 step on the other side that now has me thinking after reading this post. block was line honed, and clearance changed when caps were torqued up so maybe the caps have been machined bad.

I am doubting all these blocks were " machined bad". Look at what has been mentioned here, and you will find your problem.

With main studs, you may have to ream the main cap bolt holes slightly larger