Not an LS builder, but I build 1200 hp naturally aspirated Fords. I would run coated standard bearings in the mains. As you say, your bearing clearances will grow when hot.

On my all-aluminum FE's, which have a 2.750" main journal, I will set the mains at .0020".

 

Thanks Brent, good feedback. I'll unbolt this stuff and torque it all back up with a set of non-X bearings to see how they measure out.

What weight oil do you run in those Fords?

 

10W30.

 

I have a 416" stroker LS that uses a Manley crank in an aluminum LS3 block. It's a dry sump motor in a old ASA road course stock car. It was built with main clearances of .0022 and a few at .0023. Steel rods all at .0023. Cleavite H bearings. It holds about 14 quarts of oil. I use a racing synthetic 10w30 mostly, with a few 10w40s thrown in. So it ends up a hair thicker than 10w30. Bearings have always looked awesome.

If you have a great crank... round, not tapered, not flexing... I wouldn't go on the large size of clearance. Tighter bearing clearance spreads out the load better on the oil wedge.

Considering a typical racing/performance clearance of .001" per journal inch.

Take a hair away for:
Aluminum block

Add a hair for:
Crappy crank that is tapered, out of round, going to flex
Using thick oil as a crutch

So, assuming you have a really good crank, using 10w30 racing oil... I would think you would want to be a hair under .0025" on the mains.

 

Good recap.

 

So I pulled all the X bearings out and fit a set of coated non-X bearings. Now measuring .0025 .0026 .0020 .0025 .0025 (red numbers in pic, black were last night).

Sounds like I could stick half an X in #3 and be about where you guys suggest.

 

So if you have a 2.559" main journal diameter, I'd run around .0020". I had to look up the main journal diameters. As I mentioned, I run .0020" on 2.750" journal FE's with aluminum blocks.

 

Yeah, I'd think you'd be fine with all around .0025