WC bearing clearances

[montidale]

I took apart a spare WC engine. I have to get the timing gears off of. The timing gears look good. Looking at the crankshaft on the donor engine. It looks to be in better shape and it has not been ground down. So I think I’m gonna use the donor crankshaft. I’m checking the clearances on a couple of bearings with plastic gauge, The clearances are running around .004. I checked the clearances on the engine that was originally in the tractor and they were about the same. I’m wondering if .004 is too much clearance. I’m thinking about getting a 0.002 oversize bearing that they sell on this site for the rods. Maybe get a standard size set for the mains. The clearances on the main is a little looser than for the rods. I didn’t see any .002 oversized bearings for the mains. Or is it safe just to run it the way it is. Also, is it necessary to use the brass shims between the bearing caps?

 

[rustred]

I took apart a spare WC engine. I have to get the timing gears off of. The timing gears look good. Looking at the crankshaft on the donor engine. It looks to be in better shape and it has not been ground down. So I think I’m gonna use the donor crankshaft. I’m checking the clearances on a couple of bearings with plastic gauge, The clearances are running around .004. I checked the clearances on the engine that was originally in the tractor and they were about the same. I’m wondering if .004 is too much clearance. I’m thinking about getting a 0.002 oversize bearing that they sell on this site for the rods. Maybe get a standard size set for the mains. The clearances on the main is a little looser than for the rods. I didn’t see any .002 oversized bearings for the mains. Or is it safe just to run it the way it is. Also, is it necessary to use the brass shims between the bearing caps?

If it has shims there u go. That’s your adjustment. U Are right at max. Clearance now. I Would not be using .002 under brgs as the crank don’t wear evenly all around. Pull shims to get it at least back to .002 or .0025. Everything ground new .0015 is good. And pull shims evenly meaning the same measurement from each side. And the only way u can get rid of them shims is to resize the rods to your .0015- .002 spec. Other wise they stay there.

 

[JOCCO]

I don't have a book Handy but rustred is right on the max. I would want to mic (measure)the crank look for taper and so on.

 

[4wdtom]

I took apart a spare WC engine. I have to get the timing gears off of. The timing gears look good. Looking at the crankshaft on the donor engine. It looks to be in better shape and it has not been ground down. So I think I’m gonna use the donor crankshaft. I’m checking the clearances on a couple of bearings with plastic gauge, The clearances are running around .004. I checked the clearances on the engine that was originally in the tractor and they were about the same. I’m wondering if .004 is too much clearance. I’m thinking about getting a 0.002 oversize bearing that they sell on this site for the rods. Maybe get a standard size set for the mains. The clearances on the main is a little looser than for the rods. I didn’t see any .002 oversized bearings for the mains. Or is it safe just to run it the way it is. Also, is it necessary to use the brass shims between the bearing caps?

If it has shims you need to fit the no. of shims to each bearing for proper "crush" and bearing clearances. The proper clearances are Rods, .001- .003. Mains, front, .0011 to .0037. center and rear, .0015 to .0037. This is from a reprint of the AC service manual for WD, WD45s. Same engine as WC except 45s had precision fit bearings which didn't require shims and the somewhat involved process of fitting each bearing by shimming and filing. You need .0015 "crush" with them clean, dry and finger tight. Then check clearance with plasti gauge and file and adjust the shims. to get the proper clearance. and check plasti gauge again to confirm.

 

[montidale]

I measured the journals on the rods and crank shaft mains. and also used plastic gauge. Clearance on the mains where .006. So I’m gonna have to take it to the Machine Shop. I was hoping not to have to machine the crankshaft. I’ve got it down this far I might as well do it right. I’m not quite sure I understand how to shim the bearings. There is no reason why I shouldn’t be able to use the old shims, right. I read the instructions in the manual, and it isn’t syncing into my brain very well. Once I get the crank back from Machine Shop and new bearings, maybe it will become more clear. Can’t be that hard!

 

[4wdtom]

I measured the journals on the rods and crank shaft mains. and also used plastic gauge. Clearance on the mains where .006. So I’m gonna have to take it to the Machine Shop. I was hoping not to have to machine the crankshaft. I’ve got it down this far I might as well do it right. I’m not quite sure I understand how to shim the bearings. There is no reason why I shouldn’t be able to use the old shims, right. I read the instructions in the manual, and it isn’t syncing into my brain very well. Once I get the crank back from Machine Shop and new bearings, maybe it will become more clear. Can’t be that hard!

You put the crank in, finger tight the bearings, feeler gauge the gap between the cap and block or rod, install shims 1 and one half thousands less than the gap, Plasti gauge, if you got .005 you would remove .003 shims and file .003 off of the bearing shell ends to maintain the .oo15 crush or "press fit". This should give you the .002 clearance that is good to shoot for. To measure how much I take off a bearing shell I put them on a flat surface, shell ends down, under a dial indicator. File carefully and evenly. If you want more or less clearance you can adjust shims and filing. Sneak up on it, you can't go back. If the block and rods had shims you need to shim too. Only way around is to resize the block and rods at a machine shop and use bearings of the actual size.

 

[DrAllis]

If the crankshaft main journals are reground undersized, the machine shop will get you new undersized bearings to match. You must also order new SHIM STACKS !! to start from scratch. The shim stacks are four laminated shims that are .0025" thick for a total of .010" total. New crank journals + new matching bearings + new SHIM stacks. That's the way it is done.

 

[montidale]

OK, now it’s starting to sink in. I have use shims on babbitt connecting rods before, but nothing quite like this.

 

[4wdtom]

OK, now it’s starting to sink in. I have use shims on babbitt connecting rods before, but nothing quite like this.

Yes, you just need to adjust to get the clearance you need and maintain the "cursh". too little crush and the bearing shells could spin or be loose. Too much and you could buckle the insert.