[AG]

Rod journals are std at 2.500", couldn't find any 0.001" oversized bearings. It's an aftermarket crank and the OD of the rod journals are on the small side hence the big oil clearance. Anyone that has run this big a rod oil clearance? Thanks all for the replies, trying to make this work.

[mgarblik]

Both Butler Performance and Rock Auto show -.001 bearings available on their web sites. I imagine other vendors have some too. That would enable you to dial in the clearance closer to what you are looking for.

[Sirrotica]

FWIW, I once had a 301 that I slammed together that the crank was .010 under on the rods only from the factory. The mains were standard. I put standard bearings in it inadvertently and drove it about 50 miles. Other than low oil pressure at idle it was surprisingly quiet and when I took it back apart I finally realized that Pontiac had put it together with a undersized crank with Moraine factory bearings.

I just swapped the standards for .010 bearings and it was fine. No metal transfer, and the rod throws were clean, and round. Now this was just highway driving, and not hammering it, but with .010 + oil clearance I was quite surprised there was zero damage and lack of any unusual noises.

[AG]

Originally Posted by mgarblik

Both Butler Performance and Rock Auto show -.001 bearings available on their web sites. I imagine other vendors have some too. That would enable you to dial in the clearance closer to what you are looking for.

Yes, there are 0.001" under for extra clearance but no 0.001" over to reduce clearance. Wish I was dealing with 2.200" journals.

[mgarblik]

Originally Posted by AG

Yes, there are 0.001" under for extra clearance but no 0.001" over to reduce clearance. Wish I was dealing with 2.200" journals.

I believe you will find that a set of -.001 bearings are what you need to tighten up the clearance a little. This is based on a crankshaft that was ground small, say 2.4992" as an example. The same way a -.010 bearing is made for a crankshaft ground to a nominal 2.490". To get extra oil clearance, you would need a bearing marked "X" for extra, or some mark them +.001 for a crankshaft that is too large like 2.5008" for example. Either way, I think both are available. Just a little harder to find for a Pontiac. Good luck with your build. I also wish you had a nominal 2.200 rod journal. I keep STD., +.001, -.001, -.009, -.010, -.011 in stock here.

[AG]

Originally Posted by mgarblik

I believe you will find that a set of -.001 bearings are what you need to tighten up the clearance a little. This is based on a crankshaft that was ground small, say 2.4992" as an example. The same way a -.010 bearing is made for a crankshaft ground to a nominal 2.490". To get extra oil clearance, you would need a bearing marked "X" for extra, or some mark them +.001 for a crankshaft that is too large like 2.5008" for example. Either way, I think both are available. Just a little harder to find for a Pontiac. Good luck with your build. I also wish you had a nominal 2.200 rod journal. I keep STD., +.001, -.001, -.009, -.010, -.011 in stock here.

Got it. On Butler's site it stated," -0.001" extra clearance." If that means it will tighten up the clearance I'll get them.

[Formulajones]

What mgarblik described is what I do in situations like that. You may only need to mix half shells like he said, just takes a little time to find the right mix that gets you where you want to be.

I had a similar problem with a new aftermarket scat crank on a recent build 6 months ago. Rod journals were a hair on the small side and I didnt like the clearance. It was either send the crank to be turned to one of only a couple crank machines in the state, spend $300 and hope it comes back right, or buy another set of .001 under bearings and start mixing shells.

I opted for the latter and it worked out fine. I ended up with .0022 to .0024" after a couple hours of mixing and measuring and a set of rod bearings were only another $150