Main bearing housing measurements

[Light]

I measured my main bearing housing yesterday.

After calling ARP and having them tell me to torque to 60 pounds (does anyone find this a bit excessive? Seeing as how stock is 38.)

I found that measuring 12-6 was 1.5 thousandths smaller than 3-9. But they were all a perfect 1.5 small. Even after only torquing to 40 pounds they were the same.

Is 60 pounds too much?

And were the housing for some reason designed that way? Because I was taught that the housings were round but the bearings were eccentric.

[Tower240sx]

If you are using the ARP main studs you need to align hone/bore the mains to account for the extra tension on the mains, that's why they work better.

[Light]

But it didn't deform even when I torqued to stock spec.

[Tower240sx]

because it was bored originally at stock torque, that is the condition under which you want the hole round right, at installation?

the increased clamping load causes distortion (think about torque plates for honing a block) same Idea, you want to recreate the stresses and distortion of the assembly, at assembly.

[Your Mom]

If you are using the ARP main studs you need to align hone/bore the mains to account for the extra tension on the mains, that's why they work better.

x2

[eazye2000]

I've never had a problem with my KA-T torquing the mains at 60 ft/lbs.
I also had my machinist double check this new 'hype' of the mains distorting. He said there was no change when torquing the studs at stock, and 60 ft/lbs.
I just had my crank cut .010" on rods and mains so that he had fresh stuff to work with when measuring. (custom oil clearances set)

Take it for what you will. I'm not a machinist, but I have beat on my motor very hard. And have torn it down quite a few times and haven't noticed any failure in that area due to torquing the mains to 60 ft/lbs.
But as always, I'm sure someone will disagree.

[Light]

So I need to line bore the housings then?

[Tower240sx]

Correct

[Light]

Hmm, so what do I hone them to then? Stock size? Do I have to shave the crank at all?

[eazye2000]

You don't have to do anything to them. Don't line hone/bore it. Just put it together and torque the studs to 60 ft/lbs.
Just make sure you have the original main girdle for your motor. You can't use another motors girdle.
The only thing I did out or the 'norm' was torque everything in 5 or 6 steps. So on the mains, I started at 10 ft/lbs, then 20, then 30, 40, 50, then 60. I do that with pretty much everything I put together.
Again, my $.02
And I'm sure someone will disagree.

[Light]

Well seeing as how they aren't round puts up a red flag. 1.5 thousandths smaller makes a big difference correct?

[Tower240sx]

yes,

Please don't disregard data for some E-guys personal feelings,

Bottom line, you want the mains to measure round at assembly torque (whatever value that is) without bearing shells installed.

[Light]

So I will be boring to stock measurements then.

[Tower240sx]

yeah finding bearings for anything else would be impossible

[Light]

As for bearings now, it ACL coated "race" bearings in it, I assume for high RPM. But what of regular Clevite bearings? Would they work for 300-350 hp? The ACL's are on back order.