I know the LT1's are internally balanced. My question is are they balanced to the engine? I've run into a snag and am considering swapping the crank from another LT1 I have into the one I'm working on. I know I would have to replace the bearings and would want to do the rear main seal, but I'm just not sure about mismatching crankshafts and blocks. What do you guys think?

 

The block doesn't move, and so is not involved in balancing.

Rods and pistons are a different matter however. The rotating assembly should be balanced as a unit, apart from the damper and flywheel, which should NOT be touched or otherwise molested in any way during the balancing process.

 

if you are taking a stock crank and putting it in an engine with stock rods and pistons, it will work just fine... if either of them has been balanced in the past, then you are more likely to have issues. if in doubt, plan on spending a couple hundred $$$ to get it balanced- which to me is always worth doing if it's an engine you care about and you will be keeping for a long time.

 

I think i read u want to swap LT1 crank for LT1 crank w/o spending any $$ for testing/measuring.
well LT1's rods and pistons are pretty accurate weight wise - i expect them to be within the same spec on any LT1. Beware of the "regular" 350 crank as it has the same casting number but is balanced for heavier pistons. I believe u have to spin the crank and add weights to get a rotating weight to compare cranks. But if the rods and pistons are close then all the cranks should be also.

Depending on use and my financial situation if i knew i had a LT1 replacement and use was just for the street i would just swap it if money was tight. If origin was unkown and used for any kind of performance use then i would drag all the parts to the machine shop for a balance.

 

Thanks for the responses guys. Had a bolt broken off in the crank, but took it to a shop, they fixed it all up and I didn't have to tear it back down. Little bit of advice, if this happens to you, don't try to take it out yourself. I had the hub cranked down into place, 1/4" away from seated, and the bolt I was using snapped like a broken condom. I had to wait patiently all weekend, but found a great shop here in Louisville Ky, they had me all wrapped up that afternoon. $80 even. Worth every penny.