Undersize main bearing question

[240ZMan]

I'm getting ready to reassemble my '80 L28 block. I had the crank ground .010 undersize and ordered bearings to match. However, when I set the crank in the block the middle journal (#4) that has the special bearing for dealing with thrust is so tight that even before I put the caps on, I can't turn the crank by hand. My suspicion is that the thrust surface of the center bearing is also expecting the crank's surface to have been ground .010, and that the crank shop didn't grind that surface.

I called the parts house but they were of no use to tell me if the bearing expects the thrust surface to be ground like the main journal surface. And the shop is closed (Saturday).

Anyone know what's customary for grinding cranks? Should the thrust surface be ground down just like the journals?

[JZM]

Going off what you are saying,all you will need to figure out which side of the thrust bearing is too tight and get some 400 grit wet/sand paper and a very flat serface and lightly wet sand/scuff the thrust bearing serfacetil you get the proper clerances.

crank shaft free end play is-STANDARD@0.0020 TO 0.0071 AND LIMITED TO 0.0118in.

This is how we do it in our machine shop..we do not resurface that part of the crank shaft.hope this helps.

JZM..

[240ZMan]

Wow, that surprises me that I need to sand down the bearings to fit. Given the kind of tolerances here (.005" between min and max), I'm a bit uncomfortable sanding by hand.

Is this how all undersize bearings are delivered? I'm wondering if there is something wrong with this bearing?

I don't mean to challenge your advice, JZM, it's just not what I expected

[JZM]

Wow, that surprises me that I need to sand down the bearings to fit. Given the kind of tolerances here (.005" between min and max), I'm a bit uncomfortable sanding by hand.

Is this how all undersize bearings are delivered? I'm wondering if there is something wrong with this bearing?

I don't mean to challenge your advice, JZM, it's just not what I expected

No challenge.I understand your concern but it's really no big deal to do.

I stock ACL,NDE,MICHIGAN,TAIHO,TOP LINE,ROCK.CLEVITE AND ITM rod and main bearings, I just test fitted a 0.010 undresized crank in an F54 block and checked thrust clearance and only the ACL AND THE ITM bearings did not need to be touched up.sometimes its just going to happen.you can send the bearings back and get some more or go to a differant brand that will suit your needs better.hopefully we are talking about the same thing.please check your block and your crank very good for any defects/burrs or debris.Lots of people have the misconception that hey if its new its got to be right or perfact, in the automotive/machining business that rarly true and you need to adjust as best you can.thats why we call it machine work.

What brand of bearings are you using?

Whats your main bearing clerance?

JZM..

[240ZMan]

These are Hi-Tech sold by Checker, I believe made by Clevite?

I haven't put the caps on yet to measure any other clearances. I stopped when I couldn't turn the crank without any caps on.

In looking at the crank I can see why you don't turn the thrust surfaces. There's barely any material left to remove - looks like you'd be on the unfinished portion of the crank before you knew it.

The thrust surface on the bearing is copper in color, and it looks to be just on the surface. The rest of the surfaces are silver in color. Does that sound right to you? Any problem with taking .010 off of it?

[240ZMan]

Just finished installing the crank. Took almost 3 hours. Following JZM's suggestion I wet sanded the thrust faces to make them consistent from side to side and between the top and bottom bearings. They seemed to fit well, but after assembling everything there was less than .002" clearance. It turned easily, but I did the right thing and tore it all down, and sanded some more