Main bearing clearences

[Malthael]

Spend the 300 and have the crank polished.You're better off having a bit more clearance then not enough.Tight and she's gonna spin a bearing,then you're back to square 1 spending a pile of money to do it right.
You can always compensate for a crank with a bit looser clearances with a thicker oil,you can't compensate for a crank with clearances that are to tight.
Your call but i think you're crazy by not having the crank polished,and wanting to stick new bearings on a high milege crank

And I don't disagree with you on just running an unpolished crank on new bearings but I polished it at home with a jig I made using sand paper and 2 drills with a nylon strap

 

[Malthael]

Just not a whole lot just enough to clean it up not remove a specific amount of material

 

[Wild one]

And I don't disagree with you on just running an unpolished crank on new bearings but I polished it at home with a jig I made using sand paper and 2 drills with a nylon strap

Well then keep polishing till you get the proper clearances. Unless you're jig spins the crank at the same time your polishing,odds are you're gonna end up with out of round journals. You don't polish a stationary crank,you always want it spinning when you're polishing it.
Good luck with your endevours,but i think you'd be better off having it professionally polished

 

[Malthael]

No it spins the crank with a gear reduced drill at a steady rpm I was just going to run the race bearings which give me .0023 clearence because having to take off .0005 at home is to much. I mean I could just run the tri metal race bearings

 

[Malthael]

I mean what's your experience in using tri metal bearings? I measured each journal in 7 different spots and got the exact same measurements so there still good, but yes I wouldn't polish it .0005 smaller at home, I'm just using it to clean the crank really maybe a .0001 at most was taken off if that.

 

[Wild one]

I mean what's your experience in using tri metal bearings? I measured each journal in 7 different spots and got the exact same measurements so there still good, but yes I wouldn't polish it .0005 smaller at home, I'm just using it to clean the crank really maybe a .0001 at most was taken off if that.

Tri metal bearings used to be used all the time by factories,they're okay but usually by 70,000 or 80,000 miles they're wore out.
Well by your pics it looks like you did a pretty good job of polishing it at home

 

[Malthael]

Tri metal bearings used to be used all the time by factories,they're okay but usually by 70,000 or 80,000 miles they're wore out.
Well by your pics it looks like you did a pretty good job of polishing it at homI figured that's why

You know what is super unfortunate though the clearence on the rods bearings being .003 I need to get the damn crank ground now since no manufacturer sells bi metal bearings in any size accept standard or .010 undersize so back to the machine shop it is, really annoying that you can't get oem bearings in any other size like +/-.001

 

[Wild one]

You know what is super unfortunate though the clearence on the rods bearings being .003 I need to get the damn crank ground now since no manufacturer sells bi metal bearings in any size accept standard or .010 undersize so back to the machine shop it is, really annoying that you can't get oem bearings in any other size like +/-.001

Are you sticking new rod bolts in the rods,if you are you'll want to have them re-size the rod ends to

 

[Malthael]

Are you sticking new rod bolts in the rods,if you are you'll want to have them re-size the rod ends to

Yes I am using ARP rod bolts but Are you positive I need that I measured the rods and they are in spec not even max difference on being out of round was .0002 which is within spec when fully torqued down or should I have them checked? Since they do have cracked caps that makes it even more resilient to them getting egg shaped or being out of round

Edit: I almost wonder if it would be better to get bearings with .002 backing which would solve the clearence by taking .001 off the rod big end and make it round if it isn't and make the oil clearence .002. or the bearing would crush improperly in the rod and be all out of wack.

 

[Wild one]

Yes I am using ARP rod bolts but Are you positive I need that I measured the rods and they are in spec not even max difference on being out of round was .0002 which is within spec when fully torqued down or should I have them checked? Since they do have cracked caps that makes it even more resilient to them getting egg shaped or being out of round

Edit: I almost wonder if it would be better to get bearings with .002 backing which would solve the clearence by taking .001 off the rod big end and make it round if it isn't and make the oil clearence .002. or the bearing would crush improperly in the rod and be all out of wack.

The rods should be resized if you're using ARP bolts