devilfish

Correct me if im wrong.

( for 1pc cranks )

In theroy you should be abel to get a new OEM flexplate, or a new ( if they still made them ) OEM DMF flywheel, and bolt it on to your engine without re-balance it?
As the 1 pice cranks are external balanced at the rear, and the "offset" balance weight on the flywheel or flexplate should be the same?
And Therefore interchangeable??

I know that on the DMF you have small balance weights you can insert.
I guess GM used them for finetune the balance.

I need to verify this before I get a "new" DMF for my motor.

CHeers

Tom400CFI

Yes, that is correct. Note that the flex plates do not have a provision for the balance weights to be added/removed that the DMF has, so I guess the standard weight on the flexplate is "good enough", but the DMF needs to be "fine tuned"? I submit that any 1pc RMS flywheel or flexplate is good enough.

.

devilfish

Thanks for the reply..

Do you think the extra balance weights on the DMF where there to finetune the FW to match a certain engine on the construction line?
Or did they ( GM ) use the extra balance weights to get the offset balance perfect and the same on each FW?

Reason I ask is, if I get a new/used DMF, should I move over the extra balance weights from my old FW, and put it on the same location on the new/used one? Or just leave it?
Thanks

Tom400CFI

*I* think that they extra weights were to taylor a flywheel to each particular engine, and that all flywheels, sans weights are the same balance.

I think popular advice would be to move your weights over from your old DMF to a new one.

What *I* would do is install the new DMF w/no weights, start the engine and see what it feels like. If there were a noticeable vibration, then I'd pull the tin inspection plate and install the weights in the proper locations, from your old DMF.

WVZR-1

You would need to paint or ink the locations of the pin holes old/new before installing the flywheel to do this easily BUT it's likely the thoughtful approach to replacing it on a stock build and "off the shelf" clutch parts also. I like the thought!!

NEW PINS!! I don't believe you can remove them on a DMF

devilfish

I have now ,successfully, drilled out the pin weights from my "new" FW.
It was surprised how easy they came out..
It was 6 total.

I will install the FW without those pins,as you said.
And i also painted the locations of the pin holes, so I can install new pins if needed ( good tip ).

But this made me think about all of those that convert from a automatic to a 6sdp. And also those that convert to single mass FW.

For those it will be a "hit and miss" if the new FW is perfect balanced or not i guess?
On paper a 1pc Findanza ( as a example ), steel FW would have the correct off-set balance to fit a 1pc crank. So according to Findanza its a "bolt-on" installation?
Confusing..

Perhaps its just "good enough", and 95% will not notice the small imbalance? I dunno...

Cheers

Tom400CFI

I believe the popular thinking is that any 1 pc RMS flywheel is "properly balanced" for a 1 pc crank, but the issue is that not all 1 pc LT1 engines end up making it out of the factory, correctly balanced, and the weight pins are a band-aid fix that the factory implemented. I'm a bit skeptical of this for several reasons, one being that I've swapped around flywheels in the past w/no imbalance issues, two, the flex plates for automatic LT1's have no provisions for "fine balancing pins" so are automatic LT1's better balanced from the factory than manual ones? (no). and third, it takes quite a lot of imbalance to make and engine vibrate. One time, I mistakenly installed a neutral balanced (2 pc RMS flywheel on a 1 pc motor. THAT vibrated pretty badly by <2000 RPM. But in that case, there was a pretty sizable chunk of metal missing, that was required to balance the thing.

SO, if you buy a fidanze 1 pc flywheel or any other brand (including a GM one) it should be properly balanced for a 1 pc rotating assembly. If there is vibrations, then I think the assumption is that the problem is in the rotating assy, from GM.

Tom400CFI

That would be my contention as well.

WVZR-1

I believe the fact that a "dual-mass" is exactly that, an assembly and NOT a single piece the additional balance by using the pins on the circumference is a "fine tune" that may or maybe not be required.

I've had a couple LT5 DM wheels and both had three pins only. I didn't note the position on the first one so I wasn't able to compare.

The LT5 harmonic balancer also has provisions for the "fine tune" using pins.

devilfish

So for the record, if anyone should do the same as me.

If you get a new or used GM DMF, take out the weight pins ( its easy ).
Look at your old DMF, and with a pen, mark on your new DMF the locations of the pins.
Install the DMF on the car.
Should you get vibrations, pull the tin inspection plate and install the weights in the proper locations.
Done!

If you convert from a auto to 6spd. It's really not much you can do.

Take out the weight pins from the DMF you going to use for the conversion ( to keep it as neutral as possible to the 1pc rear off-balance ), and keep you fingers crossed.

Same if you convert to a singel mass fw. Not much you can do I guess.

I heard about people that take their old DMF or flexplate and match-balance it to the new FW.
I guess this will be a bulletproof approach.
But I dont think many do this. And you need a good machine shop.

Did I miss anything?

Cheers

devilfish

Did you take out the weight pins on the flywheels before you installed it on another engine? Or did you just leave it and installed it "as is"...

Tom400CFI

I didn't start w/a DMF. I used a flex plate, a flat OEM flywheel, and a LT1 F-body flywheel on one, 1 pc RMS engine...never had balance issues w/any of them.

WVZR-1 may very well be right that the pins are to balance each particular DMF itself, but that is not what *I* have read and I don't see why the manufacturer couldn't properly balance each DMF as it was made, same as any other flywheel.

My point was that I have READ, that the pins are to correct imbalance issues w/the LT1 rotating assy and I can't see how that is right, otherwise, most any automatic LT1 would have balance issues, since the flex plates do not have provisions for any balancing pins.

From my perspective, all this stuff about balance pins is hearsay, which is why *I* would install the FW sans pins, and see how it runs.

devilfish

Got it..

Thanks for the help

I will report back when its time to fire it up..

Best Regards

Anders...