Yes if the flywheel was balanced you would see overwhealming evidence of the weights removed and possibly a drilled hole or two.
Yes it can cause what you are experiencing.
Not sure what they're smoking... I take it the crank you have is for a one-piece rear main seal? Whenever you have an engine internally balanced for both front and rear your external pieces that run off the crank MUST be zero/neutral balanced.

 

If his crank is an internal balance crank, he needs a "0" balanced flywheel, if it is the external balance crank(like all stock 1-piece rear main cranks, and 400 chevy's) then he needs a weighted flywheel. Either way the crank should have been spun with the flywheel in place - any doubt would have been eliminated then.

 

If you're using the stock flywheel, you can easily see if its been balanced or not. There's a counterweight cast into the outer perimeter, on the backside. If it was neutral balanced, the counterweight would have to be machined off. When I bought my SPEC billet flywheel, it came with a bolted on counterweight. All I had to do to neutral balance it was to remove the three allen bolts holding on the counterweight, remove the counterweight and re-install the center bolt to make up for the missing metal in the other two bolt holes.

I'll bet that if you remove your starter and the bellhousing cover plate, so you can see the backside of the flywheel, you can rotate the engine to determine if the counterweight is there or not.

 

Yes it is a 1piece rear main crank. Come to think of it, I remember seeing the cast in weight that you speak of. It looked like a rectangular block basicaly along the outside of the flywheel.
Perhaps I can get that off myself and see how it goes from there. I will pull the inspection cover/start ASAP and figure out whats going on.
Would sure be nice if thats all it is....
Thanks a bunch guys seriously

 

There's no way that you're going to remove the cast in counterweight by yourself. You'll have to take the flywheel to to a machine shop where they can chuck it up in a lathe and cut it off; then it has to be balanced.

My thoughts on that were, I'm going to spend all that money to fix the stock cast iron flywheel, when for just a little more I can get a brand new billet piece that's not apt to explode unexpectedly at high RPM. Hmm...a no brainer.

 

Got a new RAM Billet Aluminum flywheel on the way. Made for an internal balance setup already the guy said so it will be a direct bolt in. We'll see if this cures my problem

 

Even if the flywheel states it is neutral balanced you should take it to a machine shop to make sure anyway.

 

I was debating rather to or not but now I think I will.
Thanks

 

I would not bother taking a brand name neutral balance flywheel to have the balance confirmed. That's one of the nice things about an internally balanced RA. You can simply pop new flywheels/dampers on and off w/o rebalancing.

Rich

 

The SLP LT1 flywheel I bought recently was billit, but not SFI certified. It was only like $180, clearance item. $60 more to have it zero-balanced, with pressure plate & bolts checked & indexed, too. Lighter than stock. Might be a good option for you instead of the cast piece.

Centerforce pressure-plate was near-perfect out of the box, as expected.

EDIT: I just noticed you got a RAM. Good luck, I think it'll fix you up!

 

i had my assembly balanced then used the flywheel that came with the mccleod kit.

 

Well thanks for all the input guys but this has become one of my more minor problems after tonight...
Took the car for a short drive tonight, it started getting low on power (even keeping it under 2500rpm i noticed) then started missin off and on a few miles later. I popped the hood to look for anything obvious and figured out it had been puking coolant out right by the rear passenger side head bold down onto the starter.
So about that time I decided to take it back to my work and it would smoke like a train whenever i'd take off or lug it (always a good thing).
Got it back to the shop, was running smooth just no power etc so ive decided iam gonna use dads trailor and haul it to GMR speed this weekend-assuming i can find some contact info on them or a website.

I think its time to let someone who knows what they are doing with an lt1 to work on it and get it done RIGHT. Iam to the point now where money is not much of a concern, iam already gonna be paying it off for a while so i wont mind paying it off a little longer as long as its done right.
I'd like to get it all squared away and dyno tuned when its there, that way I know nothing is wrong with it. Dont want to risk damaging a almost $14000 engine more than it already is

So any info on GMR speed would be a help. Their website takes me to some street racing videos thing now and google does not come up with anything either. A buddy of mine i used to talk to swore by GMR speed and since its only about 2 hours away it sounds like the best option right now.

Any thoughts on this or opinions always appreciated. Thanks for all the help so far guys youve done a greet job

 

Most probably they balanced it at Eagle to the common 1 pc. RMS internal in the front and to a late model flexplate/flywheel in the rear since most people with LT1s or the late model 1 pc. RMS will reuse their oem flywheels or flexplates.

Because of this you are gonna have a vibration with your internal balanced flywheel for sure. You could try a stock one just to see or ask the people at JEgs what they got from Eagle? You can have Eagle balance it either way if you tell them but who knows what Jeg's told them.

 

I'm just paranoid. Lots of money to be spent so the price to check the balance on a flywheel means nothing.

 

Well, it certainly can't hurt to check. Just a difference of opinon. I certainly have no problem spending $$$ on my projects (that's for sure and then some) but I hate to "waste" money.

Rich