98 Silver Bullet

iTrader: (28)

I'm building my engine and just got the crank installed and torqued. Turns very smooth and easy (one finger on the timing chain sprocket). I know the recommended bearing clearences are tight (.0007-.00212 according to the Helm manual) compared to other small blocks. I used
"Plastigauge" to check my clearances. They measured .001-.0015. I know that is within GM specs, but would any of you experienced LS1 builders be concerned about that being too tight?

Thanks

S_J_H

those factory clearances are Ok on the big side, Not the small side! If It were my motor I would want to see about .002-.003. No more than .003 though. .001-.0015 is bit tight IMO for any high perf motor that will rev.
I am using Fed-Mog 3/4 groove race bearings on the crank. I am at just under .003" on all the mains and my crank is stock.
Steve

Reckless

iTrader: (9)

Steve,

I just assmebled my bottom end last week. Since I used an unused crank and stock bearings, I didn't have the mains mic'd. I used Platigauge and got similar results to you.

What the other Steve said is true. For high HP, you are better of being .002 to .003 on the mains. I will take care with mine until I have some miles on it. The last motor I built (for boost) had .002 to .003 on mains and rods (checked with micrometer) and it is still going strong after repeated 10+psi dyno and track runs.

C_Williams

I respectfully disagree with the posts above stating .003 as an acceptable clearence. Too much unless we are talking about an iron block.

.001-.0015 is more than acceptable.

Reckless

iTrader: (9)

Oooops....well the last two motors I have built were iron blocks My bad. But many of the reputable builders insist the LS1 engines like the loose clearances for high HP. Just restating what I have been told.

98 Silver Bullet

iTrader: (28)

Thanks for the posts guys. I have taken my crank out twice because of my concern. I guess what I'm used to is those clearances for iron blocks. I had the crank polished so I bought .001 under bearings. The machine shop said they took very little off when they polished it. I checked it again this morning and I got around .0015 for all of them. I'm wondering if some of the problems with low oil pressure after the engine warm could be related to clearances being too large? Just a thought. Also, something else I heard, with these LS1 engines having crank and cam position sensors, you don't want your clearances too large.

Thanks again!

Z-Rated

Where can you find the torque specs for the main bolts and the rod bolts>?

98 Silver Bullet

iTrader: (28)

If you are using GM bolts, the mains are 15 pounds then 80 degrees. The rod bolts are 15 pounds then 60 degrees. If you use an aftermarket such as APR, they will have their own instructions. I'm using APR rod bolts. They want you measure the stretch on the bolt. If you have no way to do that then you are torque to 45 pounds, loosen and repeat two more times.

robertbartsch

I have the LS1 spec in an Excel document...

e-mail me if you want it...

robertbartsch@kpmg.com