Bearing Clearance ???

Do a search..Plenty of info on this out there. IMO it depends on whether you're building a race engine or a driver.
 
Most double duty motors call for 1.8-2.0 rods. 1.5-2.0 mains
machinist wont believe this and love giving Chevy clearances.
 
I was asking this same question at one time & after alot of research (both on here & actually talking to a few extremely helpful Turbo Buick engine builders) went with .0015-.0018 on both mains & rods.


The Darkside:cool:
 
Run 'em tight enough to make her scream and moan! Wait a minute... wrong board! :D

I would defer to the Guru's on this..

Conley, Anderson, Cramer etc. I want mine like that when I build it eventually. 80% street and 10% race and 10% static display!
 
Well according to one of my bestest friends, the factory set rods and mains at .0015 or less. I would consider GM a guru...

Blown/injected..Stock oil pump or dry sump?
 
All new parts but stock oil pump.

Considering going to hi-volume. The cam I have has no groove in the front journal so that should help deal with the extra forces being applied due to the extra oil being pumped.

I kinda want to see how the oil pressure looks with the stock oil pump. I do not want to mask any issues by cranking lots of oil with the big pump. Like to see the pressure jump like a tach.

Machine shop had the mains at .0032 and assured me it was fine but I got some +1's to bring it down a bit - this is with a forged steel crank - stock rods
 
Power Source says somthing about .003...

I know im gonna get "thats for a high rpm race engine" too.Fact is,some have built em that lose and they do last.I know Intercooler on was saying he set his and JBanning's engines up like this.
 
The Buick "Power Source" has blue print data from a variety of engines, right in front of the book. The "Turbo drag engine" with all Buick parts (not Stage) has about 0.002 to 0.0025 on both mains and rods. The turbo Indy engine, with a forged crank, and Carillo rods, has 0.0024 to 0.0025, rods and mains. And the engine with aluminum rods, for a Trans Am series car, has 0.0024 on the mains, and 0.0028 on the rods. So, that's what THOSE experts used. Some of the engines were dry sump, but the turbo drag engine was improved stock oiling.

So, if I were building, I guess I would shoot for 0.002, on both mains and rods, and if it got a little looser after break-in, I would be in the right range.
 
I shoot for .002" on both. But between .0015" and .0025" on either is a fine range. :D Frank
 
Originally posted in GMHighTech
Jack Merkel Performance Engines performs many mods for the unique needs of the Buick turbo V6 engine. Due to its rather unorthodox oiling system, the engine has some unique bearing clearance needs. "Common small-block Chevy thinking manifests itself by allowing too much bearing clearance. This works fine for the SBCs, which commonly spin 6-, 7-, or even 8-thousand rpm. But the Buick motors usually spin 5200-5600 rpm max. They have very high cylinder pressures at low rpm and can produce in excess of 600 lb.-ft. of torque under 3000 rpm. If the main bearings are hemorrhaging oil pressure at low rpm, the rods are going to be in an oil starvation situation. They will overheat and this will cause a spun bearing," explains Merkel


Merkel likes to see no more than 2 thousandths clearance (1.5 is preferred) in the main bearings due to the fact that there are no 3/4 groove main bearings available for Buick V6s. (We should note here that 3/4 groove bearings should be available from Federal Mogul by the time you read this.) Oiling for the rods is very important in a Buick because six rods are doing the work of eight. Merkel says, "These engines don't see a lot of rpm so the important thing is to keep the main clearance tight to ensure adequate oil volume to the rod bearings. Typically a small-block Chevy will run a higher rpm to produce the same horsepower on the motor, so they need more clearance."
Click to expand...

http://www.gmhightechperformance.com/tech/0205gmhtp_buick/index.html

http://www.gmhightechperformance.com/tech/0207gmhtp_buick/index.html
 
In essence, as its been said here before, the oil is squished out as the little motor comes up on tork so fast at such a low rpm. I have built many small cammed Pontiacs that have instant 550 + ft lbs at 2400 rpm's, and they can show copper on bearings within 50 k miles, so I believe this theory applies to any hi tork /low rpm unit.
 
Just an aside, it's nice you can go in and change all the bearings so easily on a TR, with the engine in the car. The GN I bought last year had a replacement engine in it purchased by the previous owner from Brian Weaver. I had no idea of mileage on this motor, but it had a rear main seal leak. A few months ago, I went in, and though the bearings weren't worn out, I replaced them all while I was there. Now I know where I'm at with this particular motor.
The motor has 30 psi at idle, and 55-60 at 2000 rpm cruise.
 
Originally posted by Blown&Injected
Advance Auto for the STD + .001 main bearings - Federal Mogul's about $27
Click to expand...

Woould pluses in .010 be available?
 
no +.001 in oversize bearings sizes......too bad. That is what sucks about grinding a crank. You are pretty much stuck with the clearances you get.

Dave
 
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