USAFPILOT

So, since the current flywheel in my car is brand new, if I have the three holes filled in, will it be weighted the same as my original, before the shop sent it out to be resurfaced?

I'll have to check it I guess, maybe tomorrow if I can get it on a lift. I can just remove the cover from under the car, without dropping the trans, removing the clutch etc?

Bluewasp

Yes...

Yes, You MIGHT have to move the starter down a little.

Good luck and post what you find.

If you need weights let me know.

Tom Piper

I didn't know the LT4 crankshaft was lightened.

Here is a description from this site:
http://www.grandsportregistry.com/lt1vslt4.htm#CRANK
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SPECIALLY MACHINED CRANKSHAFT

The crank itself was improved via something called undercutting and rolling. Undercutting is the machining of a groove into the corner of a journal. Though this would seem to weaken the crank at that point, it actually makes it stronger where tensile stress is most likely to cause sudden failure. Rolling the undercut introduces compressive stress to the area. This makes it more durable, because potentially catastrophic tensile stress generated during high RPM operation must first overcome the compressive stress before that area of the crank is subjected to tension. Undercutting, a groove cut into the corner of a journal, looks counterintuitive, but makes a crankshaft stronger where tensile stress is most likely to cause failure. By undercutting and then rolling it, compressive stress is introduced. Tensile stress during high-speed operation first has to overcome the compressive stress before there's any tension on the joint. And as tensile stress is what breaks crankshafts, undercutting and rolling make the crankshaft stronger.
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I wouldn't think that would lighten it much.
Is there more to the lightening of the LT4 crankshaft than that?

Tom Piper

Bluewasp

Anything new?

Strick

I, too, talked with Mr. Killibrew about this subject and he sent me the GM LT1/4 balancing procedure. What has been said here is correct, or I sould say, I concur. Take your starter out and you'll be able to remove the inspection plate. Turn the engine over with a 1/2" drive socket on the bolt that secures the damper to the crank. There is also balancing holes in the damper.

USAFPILOT

nothing new...I have been super busy with the Air Force the last couple weeks. I still need to look at the flywheel, and I need info regarding my exact Car having been at the engine balancing shop etc. So, if anyone can help me prove my car was there, it would be appreciated. I need proof if I am gooing to try to get it finished at the dealer.

Zix

I may be seeing a couple people tomorrow that should know the name of the shop, I'll see what I can get out of them

vettman10

OK - So how about posting the balancing procedure. Please.

Bluewasp

I don't understand why you need to know if it went to the "balance shop" or not. Doesn't matter if it did or didn't. You have the old flywheel. balance the new flywheel to the "out of balance" of the OLD stock flywheel. The dealer should have checked the balance on the old flywheel before installing the new. Take the car back and have them check the balance.

Bluewasp

For all those that have been waiting!!! here it is!

Mr. Killibrew GM LT1/4 balancing procedure.

Strick

I ordered a weight set/kit when I bought my new Dual mass flywheel. It came from CMI Industries with a part # of LAC209. This was ordered through my local Chevy parts counter, but I do not know the GM part #.

BTW, that is the exact balancing procedure I have. I just didn't know how to post it.

Not all Dealerships have LT1/4 certified mechanics and they may not know about the balancing procedure. I'd bring a copy of this procedure to your dealer and explain what you have learned. Yes, most mechanics don't like to be shown how to fix cars, especially by the car owners. Just use your good people skills you have learned in the Air Force and maybe they will help you out.

USAFPILOT

I'm going to try...I'll let yall know how it goes.

Bluewasp

????? What did the dealer say?

dchildress

USAFPILOT....my '94 LT-1 is showing the same symptoms. I had the clutch replaced and the flywheel machined. Could it be that my mechanic did not line the flywheel up the same way as it came off or the machine shop knocked it out of balance?

Bluewasp

You shouldn't machine the dualmass flywheel... Needs to be replaced with a new one and balanced to the out of balance of the OLD flywheel....

FELNGR8

The flywheel can't be machined, but it can be "touched up" a little bit with sand paper and reused. Mine was, so far so good. We'll see if I get years or merely months out of it.

dchildress

HOLY GOD!!!!!

What do I do now? Should I be on the look for a new flywheel? Does it have to be balanced? Is it balanced with motor or by itself?

sickspeedvette

Well, this thread is giving me bad feelings . I have a motor out at the machine shop and I'm not sure about the balancing they're doing on it. They machined the flywheel too but I don't think they balanced the crank with the flywheel. As expensive as the DM flywheels are, how hard/expensive would it be to put in a regular flywheel or aluminum one? I already bought the new clutch/pres plate/throwout bearing for the DM flywheel.

dchildress

Bumpin' myself....still need help!

Bluewasp

Go back to the shop and tell them there is a problem. They are responsible for their work.