The LS1 is internally balanced, right? Therefore changing out flywheels to an aluminum flywheel (Fidanza) shouldn't be an issue as long as itself (as a seperate unit) is perfectly balanced correct? What about the clutch assembly?

 

You will get MANY opinions on this and there are lots of theads about it. Here's my take on it.
Swapped in a Fidanza/Spec III supposedly zero balanced. Swapped it in my driveway on jackstands.
Car vibrated like a magic fingers bed in a cheap motel.

Took it out and had it matched to my OLD assembly at a machine shop.
I am not an engineer or a physicist or a shaman or anything but I figured, if the stuff in there doesn't vibrate, and the new stuff is balanced to the old stuff, it shouldn't vibrate. I installed it and it runs as smooth as Barry White.

 

FASTGUY

Good info!!!! Thanks!

Bill C

 

I also thought the same way of match balancing but I guess my GD machine shop screwed the F up and the "match balanced" aftermarket plate vibrated like a nut shaker.

Fortunately, I ground off the weight they welded on, and the vibration went away. I got realllly lucky on that one. So I'm still lost of which is the correct method.

 

The one that works.

 

So from the looks of it if someone changes out there flywheel then they need to have the flywheel balanced to match the old flywheel, correct?

 

I'm with fastguy. IMO the only way to do it right is to yank your stock setup and have it spun. If it's dead on, great. If not the new setup should be balanced to whatever the stock unit was out.

This is the only way to ensure that it won't vibrate (assuming your stock setup does not vibrate) and I have even heard of one guy who did this and still vibrated.

GM appears to have changed their method of engine and clutch balancing over the years. Some have found that weights were put into the flywheel to counter engine imbalances which caused their zero balanced aftermarket units to vibrate.

Real PITA.

 

To confuse you even more, I had a shop install the LUK clutch/aluminum flywheel. It vibrated pretty bad. They tore it down and had the assembly zero balanced. It still vibrated bad. Took it to another shop, they pulled it apart and re-installed it, replacing the torque tube and the pilot bearing. Problem solved and I have no balance issues anymore.

 

Jeff Jeff - why did they replace the torque tube? Did you get a chance to take a gander at the old one? I have to believe that if it was the source of vibration that it would have done so before the new clutch/flywheel as well...

 

My guess would be a botched pilot bearign on the original install. That would vibrate..and chew up the end of the torque tube pretty good.

 

While researching my inpending clutch replacement I came across this.
From my 1997 service manual Book 3 of 3, page 6-255.

Engine Flywheel Installation.
Note the position and direction on the flywheel before removal.
The flywheel does not use a locating pin for alignment.
Mark or scribe the end of the crankshaft and the flywheel before component removal.The engine flywheel must be reinstalled to the origional position and direction. the engine flywheel will not initally seat against the crankshaft flange, but will be pulled onto the crankshaft by the engine flywheel bolts. This procedure requires a three stage tightening process.
DO NOT remove the prop shaft hub or flex plate from the automatic transmission engine flywheel. The flywheel, Prop shaft hub, and flex plate are balanced as an assembly. If service is required, the entire flywheel assembly should be replaced.

If replacing the manual transmission flywheel, note the location of any balance weights (relative to the position of the flywheel locating hole). Install new balance weights into the new flywheel (if applicable). Flywheel balance weights must be installed into the new flywheel in the same location as the old flywheel. A properly installed balance weight should be installed below flush with the face of the flywheel.

There is more, but I am a slooooooow typist and the manual has pictures, If you want a scan of the instructions for balancing the flywheel and the front balancer,
my e-mail is norman_koerner@sbcglobal.net, I will scan the pages and send.
Hope this helps Norm

 

You might try a search on the forum as there's been a lot of discussions on balancing issues. It's my understanding that both the stock flywheel AND the balancer pulley have been balanced to your engine. So if you change them then you need to match balance to the old one. I'd be especially careful to mark the exact location of your old flywheel and pressure plate so you get it all back together exactly the same as it came off once you match balance your new setup to the old.
John

 

NLKoerner - I have the '97 Service Manuals and did a quick scan through the tanny section last week but didn't see anything regarding flywheel balancing. But now since you posted an actual page number i'm going to check it out tonight when i get home. Thanks!

 

I had zero vibrations before this clutch ordeal started. After I installed heads/cam, the stock clutch would not hold the power very well. I needed a new clutch.

Took it to a well respected shop here in DFW and had the LUK clutch w/alum flywheel and 4.10's put in. I babied it for a while until about 500 miles. I had what I considered a bad vibration. Took it back to the shop, they said "normal for aluminum flywheel".

A few weeks later, I finally had it. The vibrations made the vette awful to drive. I insisted they tear it apart agreeing to pay if they did not find anything. They found the clutch/flywheel assembly to be off by 7 grams or so. Had it rebalanced and I picked it up. Same exact issues with zero improvement. The vibrations may have moved around some in the RPM range, but not significantly.

I took it back in, they gave me the "Normal for aluminum flywheel" and "some ls1's are balanced externally". Well, they should have know that when they did the work. I was SOL and thought my result was a new fully balanced short block.

I took it to LG Motorsports and they immediately diagnosed the problem after a 2 minute drive. Described the vibrations as "scary" and definately not "normal for an aluminum flywheel". I agreed to have them pull it apart and there diagnosis was correct. The pilot bearing was destroyed causing the torque tube to vibrate around, destroying the torque tube bushings and bending the torque tube. I have a picture of the pilot bearing, PM me if you would like to look at it.

Basically, the first shop I took it to botched the install. Not once but twice. I can't say for sure exactly what they did, but a theory is that when they reassembled it, they messed up stabbing the torque tube back in, damaging the pilot bearing (which they may have not even replaced the first time).

In my case, I have no vibrations with a zero balanced flywheel/clutch assembly (after a proper installation).

 

Jeff-Jeff - Good to know LG hooked you up on CORRECTLY identifying and fixing the issue. I'm about to get a new clutch w/alum flywheel and 4:10's installed and they're on the top of my list to do it.

 

The guys at LG are true pro's. They test their work at the race track on a regular basis unlike most tuners. They will do you right and stand behind their work.

 

NLKoerner - I checked out the pages you mentioned and sure enough it's all there in black and white. When i checked the Service Manuals last week i only looked in the "Manual Transmission - Clutch" section in the very back. I guess i should have did a better job researching.

 

Glad to have helped

 

FASTGUY,

Since you are somewhat local, what shop did you use to do this balancing? Would like it for future reference.

Thanks

 

Yes, I am interested to know as well.