What kind of bearing (rod and main) clearances are you guys running in the high hp setups (400whp+)?

I've read to shoot for 15-20 thousandths to be on the looser side aka safer

 

I'll be running .0018 for the mains & rods in the forged block i'm building.

 

Between. 0018 and. 0020. Id also recommend a ptw tolerance of at least. 0045. That's where im at with 475hp and so far so good. I had some ptw issues on the dyno with. 0035. I also had a rod bearing at about. 0015 that was on its way out fast with only 2500 miles. Good thing I found it b4 it spun

 

Im just rebuilding a block that ate a bearing a few months ago. It had a good 15-20k miles on it then I think it over boosted.

Same pistons just fresh hone, rings, bearings, and crank.

 

My mains are 0.0020 and my rods are at 0.0015. My ptw is 0.0055 on all cylinders.

 

Just so you know 15-20 thousandths is .015-.02. What you meant was one and a half to two thousandths .0015-.002. I would stay on the looser side of that tolerance though .0018-.002 especially since your running high boost. I'm assuming this is your sleeved motor i saw in the ls-t thread?

 

Ya

 

this

and PTW around .003-.004

 

is there a way to check without a dial bore gauge for PTW?

 

you need a 3-4 inch outside micrometer for measuring the pistons and then the dial bore gauge for the block... then do the math.....I will rent you mine LOL...

 

Your saying a good micrometer measuring the top of the cylinder isnt good enough? Its at the machine shop now so I'll know if its out of round

 

I like to run stock bearing clearences with or without oem bearings. If your not going to change oil weight then why run anything looser than stock specs ?

 

No its not. You should measure the entire bore from top to bottom and then again 90 degrees from the first with the dial bore gauge.

 

just run near the service limit on the stock specs, why?

more then stock rpms require more then stock clearance for more then stock cooling. don't overload the oil/bearings for a 200.000miles longevity your not going to use.

 

ive never had any bearing issues running the loose side of stock clearence and 10w30 motor oil with 9200rpm and over 400whp

 

Yeah same here. 0.0020" to 0.0025" clearance on the mains and rods with 10W-30. Lasted 2+ years until it cracked a ring land during a cold night at the track. The motor did a 11.2 @ 130mph that night.