Flywheel / Pressure plate balancing

[rbickle]

Anybody have a recommendation for a shop to balance my new flywheel and pressure plate? I'm installing a new TKO and want to make sure I don't have any strange vibes.

Thanks,
Rick

[patrickt]

Any machine shop can do that. Just make sure you know how they marked the orientation of the pressure plate to the flywheel (mine had an easy to see 'X' placed on both) so that you put them back together in the same spot they were balanced. I am told that pressure plates are surprisingly not as neutral as they once were. Of course, your engine is internally balanced and not like, say, a 428 is....

[RockBit]

Is it really necessary to balance the flywheel/pressure plate? I have heard it is not required. I would like to hear some comments from others.

[patrickt]

Originally Posted by RockBit

Is it really necessary to balance the flywheel/pressure plate? I have heard it is not required. I would like to hear some comments from others.

I never did it before putting my FE in the Cobra. But, it costs next to nothing when you have the pressure plate and flywheel sitting on the table and, sure enough, my Centerforce PP required a small bit of metal to be welded on at a certain spot. Even though my block started out life as an externally balanced 428, the rebuild with the SCAT crankshaft resulted in an internal balancing, so the flywheel was neutral. I don't know how you'd take an externally balanced flywheel and pressure plate to the machine shop for balancing -- you probably wouldn't.

[Prof]

When Keith Craft built my 331 SBF, it was highly recommended and cost very little. He said in a Cobra 427 w stiff motor mounts, an old guy like me will be bothered by the slight vibration it causes. So I sent it along when the engine parts were shipped (out of Plano TX at the time).
Paul

[rbickle]

I'll check around with machine shops. My engine is a 347 stroker. It is externally balanced with a 50 oz counterweight on the flywheel. I'm assuming that the shop can put a temporary offsetting weight on the opposite side and balance it out to neutral.

Rick

[patrickt]

Originally Posted by rbickle

I'll check around with machine shops. My engine is a 347 stroker. It is externally balanced with a 50 oz counterweight on the flywheel. I'm assuming that the shop can put a temporary offsetting weight on the opposite side and balance it out to neutral.

Rick

Or maybe just put the pressure plate on their spinning machine by itself, and leave the flywheel sitting on the table. I'm pretty sure I didn't spend more than about $75 to have mine done, but that was a decade ago....

[DanEC]

I had KC balance my assembly also. It may not be absolutely necessary but I would recommend it as you can't always count on new parts being good.

I bought a brand new Hays 30 lb flywheel for my Corvette once that was so warped it had to be surfaced twice to get it flat (first guy screwed up) - which led to balancing it too. I had a new Centerforce clutch for it and they balanced it at the same time and took a bit of material off to true it up.

[rbickle]

Originally Posted by patrickt

Any machine shop can do that. Just make sure you know how they marked the orientation of the pressure plate to the flywheel (mine had an easy to see 'X' placed on both) so that you put them back together in the same spot they were balanced. I am told that pressure plates are surprisingly not as neutral as they once were. Of course, your engine is internally balanced and not like, say, a 428 is....

Good point, I'll make sure to do that...

[rbickle]

It's going to be a Spec brand clutch and flywheel. The flywheel I ordered will be aluminum. It will only weigh 12 pounds, but as long as I have the thing apart, I want to make sure it's dead on.

[patrickt]

Originally Posted by rbickle

It's going to be a Spec brand clutch and flywheel. The flywheel I ordered will be aluminum. It will only weigh 12 pounds, but as long as I have the thing apart, I want to make sure it's dead on.

I like the lighter flywheels. My aluminum Centerforce flywheel is 17 lbs. and I have no problems with it on the street at all. You know, I don't follow SB threads or forums much, but I do find it interesting on the neutral/28/50 debate when stroking them. With some of the high end FEs, builders try and get them balanced down to just a gram or two -- so you would think just resurfacing a flywheel, would screw that up. much less slapping on an out of whack pressure plate. Internally balancing the 428 when you stroke it just makes life easier, and it's pretty common. But you do tend to see that less with SB stuff. I don't know -- maybe it's just harder to do.

[rbickle]

Now you've got me wondering if the engine balance was changed when it was built. I didn't build it - bought the car partially built with the engine and tranny already done.

I might just take the old flywheel down and have the shop make sure it's the 50oz offset.

[patrickt]

Originally Posted by rbickle

Now you've got me wondering if the engine balance was changed when it was built. I didn't build it - bought the car partially built with the engine and tranny already done.

I might just take the old flywheel down and have the shop make sure it's the 50oz offset.

OK. If you haven't had any bad vibration up until now, then I would say whatever is on there now is probably the right one for it.

[CHANMADD]

I've had guys come in with bellhousing cracking from imbalanced engines.....

[patrickt]

I think we're all unbalanced to differing degrees. Our engines, too.

[olddog]

Originally Posted by rbickle

Now you've got me wondering if the engine balance was changed when it was built. I didn't build it - bought the car partially built with the engine and tranny already done.

I might just take the old flywheel down and have the shop make sure it's the 50oz offset.

Wise Choice!

Just so you know, the serious gear heads will have the crank shaft balanced, with the Harmonic balancer and the flywheel attached. They do not intend to replace either without pulling the engine down anyway.

I would doubt your engine was done this way, but just so you know.

[rbickle]

Well, the flywheel and pressure plate are at the shop. One other thing I noticed was that someone had welded a little piece on the back of the pressure plate. This must have been for balancing, so We'll see what they say. I left them the original pressure plate too, so they can test everything.

[rbickle]

I got the flywheel and Pressure plate back from the shop. The guy said it was a real mess. He cut off the weight that was welded to the pressure plate, and also had to cut off about half of the 50 oz. weight that came with the new flywheel.

Now I'm confused. I'm pretty sure that this '95 5.0L HO engine was originally a 50 oz. offset. Maybe it was all balanced up as a unit when it was built. Maybe the balance changed stroking the engine to a 347?

So the new flywheel and pp is balanced to match the old one. Hope I don't end up taking this all apart again...

[patrickt]

Originally Posted by rbickle

I got the flywheel and Pressure plate back from the shop. The guy said it was a real mess. He cut off the weight that was welded to the pressure plate, and also had to cut off about half of the 50 oz. weight that came with the new flywheel.

Now I'm confused....

Jeez, you don't think he thought it was a 28 oz. external balanced job do you? I am told that the flywheels between the two look entirely different, if you know what you're looking at, so it would seem that would be a tough mistake to make if you're in the biz of working on that sort of stuff. Somehow, I just don't like this story.

[rbickle]

I told him it was a 50 oz. offset. He ended up balancing it all to match the balance that the previous flywheel and pp had. I'm just confused as to why it's so non-standard.