BirdIsTheWord

iTrader: (5)

I have a serious vibration issue with my car. A couple weird bits about the rotating assembly.

*Stock Lt1 balancer pulley

*Eagle Cast Steel Crankshaft NOTE (Requires a Chevy 400 harmonic balancer and the use of a stock type counter weighted flexplate or flywheel..)
http://www.summitracing.com/parts/esp-103523750

*QuickTime Balance plate
http://www.summitracing.com/parts/qti-rm-530

*Spec Steel Flywheel
http://www.lmperformance.com/705488

**Spec Stage 3+ Clutch


I bought the car already built, with a different vibration. I added the QuickTime plate, it fixed it. I had the setup on the road for about a year with a stock clutch before the throwout bearing went, and me being a broke college kid, couldn't/didn't fix it for 4 years. Now, fast forward to 2015, the rings and bearings are all fresh, The clutch is the Spec 3+ I talked about, I start it up, and I have a wicked motor vibration. The only thing I changed in the setup was the clutch, so that leads me to believe that the clutch is out of balance. Just figured I would type out this book to get a second opinion, since all of the other LT1s have gone away from the local scene and my group of friends.


For ***** and giggles, here is my motor balancing sheet.

Piston 660 g
Piston pin 1 g
Piston Rings 56 g (original rings not new)
Pin locks 4 g
Total Rod 556 g
Insert 46 g
Rotary 899 g
Reciprocating 875 g
Bob Weight 1774 g

ahritchie

iTrader: (1)

Did you change to an aftermarket flywheel recently with the new clutch? If the engine is vibrating with the trans in neutral then it's probably not the clutch.

SS RRR

iTrader: (2)

If the the engine was externally balanced via flywheel then the PP was most likely bolted to the flywheel when it was balanced. Do you still have the old PP?

BirdIsTheWord

iTrader: (5)

No, I always had the Steel Spec flywheel in there, resurfaced when I put the new clutch in.

The engine is externally balanced via that QuickTime plate thing. I hate the setup, I wish the previous owner didn't cheap out on a crank, I am to blame too when I set up again.

I do not have the old PP anymore.

Catmaigne

iTrader: (6)

All of the clutch parts are neutral from the Spec factory. The steel flywheel can be external balance with the bolt on weight or neutral without it.

bufmatmuslepants

iTrader: (3)

Broken eagle cast crank

hrcslam

This.

StealthFormula

iTrader: (35)

Yo what's up Caleb, been a long time man!

I don't trust Eagle cast cranks, Corey who used to own that dark green Formula had his Eagle cast crank break. I certainly hope that's not the case though.

BirdIsTheWord

iTrader: (5)

I have snapped cranks before, the vibration really isn't that extreme.

I don't think it is. I know the crank is a total peice of crap though.

If you would like too, stop by and check it out yourself! Shoot me a PM with your number. Its right over in Pipersville.

BirdIsTheWord

iTrader: (5)

Guys I appreciate the responses big time! Still brainstorming..

SS RRR

iTrader: (2)

Perhaps a dumb question, but did you take the plate off/install it correctly when doing the clutch?

BirdIsTheWord

iTrader: (5)

I am pretty sure that it only goes on one way, so that shouldn't be it. I know for certain it is up in there too.

BTC

Did the car sit for 4 years without running?

guppymech

iTrader: (7)

Unfortunately with the current state of available clutches for the LT1 you can't assume any of them are balanced correctly out of the box. You should get the clutch PP checked for balance. What's nice is you can use your Spec steel FW for this as with its bolt on weight removed it should be neutral balanced. It doesn't take much imbalance to get things shaking.
Here's a link to a GM Service Bulletin I found about fine tuning the balance of the clutch/FW assy on the car with the bellhousing inspection cover removed.
https://ls1tech.com/forums/manual-tr...tructions.html

When my engine was vibrating from the clutch/FW imbalance I could only detect it with the trans installed. During troubleshooting with just the FW and clutch installed (no bellhousing or trans) and running the engine everything appeared smooth but after I installed the trans then it vibrated, very frustrating.

BirdIsTheWord

iTrader: (5)

Yes, more or less. It sat for 2 years with the bad throwout bearing, with myself occasionally starting it. Then 2 years to tear down and rebuild the motor, trans, and install a new clutch.

Thank you very much. I am about to leave for Ohio for a week, after that I will come back to this and see what I can find. I'll update with progress soon.