Hi Guys, I’m doing a Clutch install on my 98 c5 6-speed coupe. I’m installing a LUK 04-905 (LS7) clutch kit. Has anyone used this clutch and did you have to shim the throw-out bearing?

Now for the balance. I took my new kit to a Machine shop here in the Vegas area. I said that I need to match balance my old flywheel with my new one. I also said that GM balances the Harmonic balancer, Flywheel and engine as a Matched set so I need to unsure that my flywheel is the same balance as the one coming out. Fultz machine shop said that is not how it works. The engine is not externally balanced and the balance marks on the new flywheel is balanced to GM specs. So….No match balance is necessary.

I need some help before I Install my new clutch. Does anyone know the real story? Is the new flywheel ok to install as is? There are only a very few Vette shop in the Vegas area so my choices are limited. Any help on would be greatly appreciated.



Thanks

 

I installed a LUK clutch last year for my 2000 coupe. I used the flywheel that came with the kit as is, with no problems.

 

Same as above for me to no issues

 

Looking at the same kit now for my head/cam/intake build.

 

I did the LS7 clutch, but used the Fidanza flywheel; no need to shim the slave. On the current Mantic 9000, I needed a large shim. Be sure to push the slave all the way back in prior to measuring. Also, if you are digging into the drivetrain that deep, consider replacing the slave. They are cheap relative to the work needed to dig out a bad one. In any event, install a remote bleeder.

 

What is the "real story" you want to know?
1. GM hot balances these LS engines when they are going into a manual trans vette. They perform an external fine tune balancing procedure. That is a fact. I can provide picture and video evidence if you need it. So the machine shop is dead wrong about that.
2. You MAY or MAY NOT be just fine with installing the FW as it comes. There is no way to know for sure. The only SURE way to know you won't have new vibrations from the new clutch setup is to have it balanced the same way the "stuff" you are removing is balanced. So that means not just the flywheel alone but the flywheel and pressure plate. If your stock stuff has no vibrations and the stuff you put in has the same balance as the stuff you take out, you get the picture? There is a chance you can put in the new stuff out of the box and be just fine, no problems, plenty of people have done it and have had no problems. There is also a chance you put in the new stuff out of the box and you have new vibrations you didn't before, plenty of people have done it and have had problems. There is no way to know ahead of time unless you know the balances of your before and after pieces.
3. What "balance marks" on the stock flywheel are the machine shop folks talking about?? There are blind milled holes on one side of the flywheel that the flywheel manufacturer drilled when they were balanced prior to shipping. Then there can be marks and/or weights installed into one or more of the 12 circumferential holes along the perimeter of the flywheel. Those would have been installed by the GM balance operators when they are externally balance checking the engine. Further evidence of a final fine tune external balancing.

You probably won't get anyone to understand what you are trying to do with match balancing, as evidenced by your current experience with this machine shop. Are you doing the clutch job yourself? If you are having a shop do it, then make sure they warranty their work and let them do it however they suggest. If you end up with problems, make them redo it until its satisfactory to you. But I would strongly suggest you have them in the car before the work is done and AGREE that there are no current vibrations.

Good Luck to you!

 

Here is a recent post where I included a build video that actually discusses and shows the balance procedure. Not sure if you might have stumbled across this during your searches. Check it out.

https://www.corvetteforum.com/forums...ghts-tips.html

 

Match balancing - never did that. Not saying that you will 100% not have trouble, but I think you will find that the vast majority of folks don't bother. This included folks that work on track cars for a living. My firs clutch (LS7) I left the stock balancer on. When i did the heads/cam/intake, I went to an ATI balancer, so I guess by default I kind of balanced thing out since the ATI figures it out. My C5Z is a track car with a license plate on it. Track to road mileage ratio is about 23::1, never had any detectable vibration.

Can it happen, maybe. Sure, anything can happen. Your mileage may vary, No warranties expressed or implied, and all that other lawyer poo

 

I just want people to make educated decisions when they are actively deciding to do or not to do something. I agree, most people do not bother with match balancing, but because they aren't aware of the unique external balancing done. They think it's no different than any other internally balanced engine.
I don't know the percentage of folks who could be negatively affected by not match balancing, I believe its fairly low, it just really stinks when you end up with vibrations because of it. Anyway, that video was one of the better build videos I found and it actually discussed and showed the external balance in decent detail.
To the OP, good luck with whichever you decide.

 

Is there any safe way to run the engine up to high RPMs without the torque tube and everything back of it not installed? This would save a lot of repeat labor if excessive vibration were felt. Got vibration: figure it out. No vibration: put it all back together. Pressure plate on or off? Maybe not the friction disc on as it needs to be centered?
(Just a thought I've had a long time since flywheel unbalance became an issue, realizing that the mechanical connections of the drive train are different from the usual front engine cars.)

 

For anyone looking for a shop to Balance your Flywheel or Extreme engine work in the Vegas area give these guys a try. I spoke to Rick about my Flywheel balance and he knew all about it. He also built his own jig to perform the balance. Ill post the results but from what Ive seen he's got everything covered.

HBR--Competition-Engines

 

It's not the flywheel alone, it's the stock fw/pressure plate assembly. Match the new fw/pp assembly to the stock assembly. Flywheel alone is only part of the system.