Picking up good vibrations...NOT part II

[Gary Morris]

Well I had some free time yesterday so just out of curiosity I took my old flywheel...see it's good not to throw things away...down to the machine shop for a check. Sure enough it's not "0" balanced and the one we put on was. So now we're trying to come up with a fix. Here is the problem. First off it's an aluminum flywheel...no clues on mfg....motor was originally built around 1990.....the steel insert is in pretty bad shape...as in we don't think it could be ground enough to clean up and since we don't know the mfg. we can't order a new insert. One suggestion was order a new flywheel. Mfg. states that now they supply flywheel with an extra weight that bolts on so flywheel can be used either way.....sounds simple....but here's the kicker....from what we can tell by looking is that for some reason they used a "0" balance flywheel and just drilled out enough material along one edge to make it out of balance so to speak to compensate for the weight they needed....I'm talking about 10 or so 1" diameter holes drilled but not all the way through. What the machinist is checking into is if someone can take my flywheel that is on the car now and match it to the old one. If we can't do that it's buy a new one and hope it's close or the motor has to come down again to balance it all over.

But..........it's still fun
Gary

[Coloradocobra]

Hi Gary,

Are you running a 428 crank? I would think they could drill out enough material to create the correct external balance correction for the 428. Does McCleod offer an aluminum flywheel already set up for the 428? You might want to call David Kee to see what he has in stock as this may be safer than compromising the flywheel you already have and you can just sell it to someone with a 427 crank.

Gary

[Gary Morris]

Yes I am running the 428 crank and McLeod does offer one like I said....it's a zero balance with a bolt on counterweight so you can use it either way.....what we're curious of is that there has been so much material taken out of the original flywheel to create the counterbalance that we're not sure if they just took out enough for the counterbalance or whether they took out addittional material to bring it all into balance and if the bolt on counterbalance would be in sync with the original. I had already talked with David and it was his suggestion to see if someone could balance the new one to the old one without having to take down the motor again. The machinist suggested a new one with the bolt on counterbalance but we both agreed we were not sure if it would be close enough or not.

Gary

[Coloradocobra]

Hi Gary,

Any good balance shop can determine the phase angle of the unbalance in your old flywheel (the position of the heavy spot with respect to the bolt pattern) as well as the oz-inches of unbalance. They can then replicate this on your new one. Based on what you have said about this bolt-on plate, I would bolt it on and then simply "trim" balance it to get it to precision. In other words, bolting it on may bring it to 28.4 oz-inches at 89 degrees (made up the angle). At 5000 rpm you would probably never feel the fact that the balance was not perfect. At the 11,000 rpm you spin that stroker, they would have to perform some creative drilling to move the position of the heavy spot a few degrees and set it to exactly 28 oz-inches (or whatever your old flywheel was). No need to tear the motor down, just replicate what you already had.

Before bolting the flywheel on, use a machinist's stone to make sure the faces of the crank and flywheel are free of burrs and check for axial runout once you have it bolted on.

Good luck,

Gary