Flywheel Comparison Before Install

[zrwhat]

Just pulled trans out of 91 # 1512 to inspect/replace clutch and Flywheel.

Was going to take the DM FW and the Fidenza to have a balance done but first my curiosity got to the best of me and I put the DM on my Hunter Wheel Balance just for kicks and giggles to see what I came up with:

The Balancer showed a .79 oz imbalance on the DM factory FW. I indexed the shaft of the balancer to the centering pin for the crank. I so noted where the imbalance was on the DM. Pulled the DM off the balance and installed the Fidenza and indexed that one as well and did the same balance test.....

The Fidenza came up @ .072 inbalance or very close to perfectly balanced, less than 1/10 of 1 oz imbalance and the DM was almost 8/10
of an OZ of Imbalance!

Although not very scientific in nature, this tells me the Fidenza is extremly close to being zero balanced and the DM was not very well balanced.

The DM also had some lateral run out on the ring gear while the Fidenza was as straight as an arrow when spun.

What do you guys think, should I have the Fidenza balanced and weighted just like the DM which I feel is out of balance or let it rip the way it is?

Common sense is telling me what to do, I want to hear from the guys who have been there and done that before I make my next move.

thanks,

Gibby

[VetteMed]

Interesting info... I have nothing to add, but will be watching the replies

[VetteMed]

I "thought" that the LT5 was internally balanced (i.e. without flywheel), whereas the LT1/LT4 were dependent on the flywheel for proper balance...?

[Jagdpanzer]

Did the DM flywheel have a trim balance weight inserted in any of the 24 weight holes?

[Jagdpanzer]

Originally Posted by VetteMed

I "thought" that the LT5 was internally balanced (i.e. without flywheel), whereas the LT1/LT4 were dependent on the flywheel for proper balance...?

Yes, the LT5 is basically internal balanced. However, during the factory production dyno testing of each engine the vibration level was measured and, if necessary, further balancing was done by inserting small trim weights in the flywheel and/or front torsional dampener.

[zrwhat]

Originally Posted by Jagdpanzer

Did the DM flywheel have a trim balance weight inserted in any of the 24 weight holes?

Phil,

I'll have to take a look at it, car is in Alexandria right now, I'm up in MD.

I dont recall seeing any added weigh in the weight holes but will confirm within the next 2 days when I come back down.

The thing that sticks out is the lateral ruout while spinning on the balancer, it appeared ther machined surfaces of the DM FW looked true, ring gear did not, wasn't a wobble, it was up and down variation you could see as it was being spun.

Did not seem to have any balance issues but then again, the entire time I've had the car, I've yet to drive it at speed since it was damaged when I picked it up and I chose to put it back together, finally got off my lazy ars and got cracking on it.

Changing the FW for 2 reasons, first is the car has 80K on it, 2nd is I got a good deal on the new Fidenza a while back and have a new Valeo clutch set up with a sprung hub disc on its way to me and should be here by Friday.

Flywheel surface on the DM was a little scortched, disc and PP looked OK and servicable but while I was in there......

Gibby

[zrwhat]

Originally Posted by Jagdpanzer

Yes, the LT5 is basically internal balanced. However, during the factory production dyno testing of each engine the vibration level was measured and, if necessary, further balancing was done by inserting small trim weights in the flywheel and/or front torsional dampener.

Guess I could always install the Fidenza without the bell and fire it up and see if the thing shakes like there's no tomorrow at upper levels, I'm sure if it is out of balance it will rear its ugly head.

With the newly installed headers and exhaust off, I think I'd be able to feel the noise....but would I feel the vibration if minor?

The thing is if the DM has moved around and worn/softened between the 2 halves in its 21 years, this could be where the .790 out of balance came from.

Like I said, surely not scientific but interesting.

Gibby

[sammy]

i have installed 2 fidanzas in zr1s just as they came out of the box and both worked great

[ALZR1]

Originally Posted by zrwhat

Just pulled trans out of 91 # 1512 to inspect/replace clutch and Flywheel.

Was going to take the DM FW and the Fidenza to have a balance done but first my curiosity got to the best of me and I put the DM on my Hunter Wheel Balance just for kicks and giggles to see what I came up with:

The Balancer showed a .79 oz imbalance on the DM factory FW. I indexed the shaft of the balancer to the centering pin for the crank. I so noted where the imbalance was on the DM. Pulled the DM off the balance and installed the Fidenza and indexed that one as well and did the same balance test.....

The Fidenza came up @ .072 inbalance or very close to perfectly balanced, less than 1/10 of 1 oz imbalance and the DM was almost 8/10
of an OZ of Imbalance!





Although not very scientific in nature, this tells me the Fidenza is extremly close to being zero balanced and the DM was not very well balanced.

The DM also had some lateral run out on the ring gear while the Fidenza was as straight as an arrow when spun.

What do you guys think, should I have the Fidenza balanced and weighted just like the DM which I feel is out of balance or let it rip the way it is?

Common sense is telling me what to do, I want to hear from the guys who have been there and done that before I make my next move.

thanks,

Gibby

I have A spare DM and A Fidanza flywheels this is preatty interesting i'm going to try this myself on my balancer and see what I get.


AL.

[zrwhat]

Originally Posted by ALZR1

I have A spare DM and A Fidanza flywheels this is preatty interesting i'm going to try this myself on my balancer and see what I get.


AL.

Al,

Did you have a chance to spin both FW's and see what you came up with?

Gibby