wobble in my 428

[xcobraj]

I bought a 428 cj engine out of a 67 mustang that was rebuilt,ran for break in time and then sat in car for about 3 yrs,last week I put on a dyno.Engine started ran great 60lbs oil press.all specs were set.The problem is it has a wobble to it like its out of balance.We swapped fly wheels just in case, thats not it.I tracked down the guy who rebuilt the engine,he said the crank and rod were balanced as assembly and should be fine.The strange thing is when you raise the rpm's,wobble seems to subside a bit.My dyno shop sez they knew the shop that balanced the set and said that their shops bal.machine was out of specs.for a long time,and thats the problem.Seems to me thats a little far fetched,I'm sure they would have gotten complaints from all over the place.I hate to pull this engine apart for no reason,but i'm stuck between the engine builder and the dyno shop.Anybody has any ideas...

[SCOBRAC]

Got a wrench?

Regards,

[Whaler]

Could be an original harmonic balancer that's giving you grief.
What do you have at that end?
I sent in my crank, rods&pistons, flywheel with clutch & pressure plate and the aftermarket harmonic balancer to a machine shop out of town.
Threw out the original Harmonic Balancer as I don't trust rubber gadgets 33 years later.

But as you say there talk that it may be an imbalance from the original balancing machine used is interesting as it would be widely apparent with more rebuilds.

Last resort is a quick tear down and check out.....all it costs you is gaskets

whaler

[xcobraj]

The lack of even worse wobble as rpm's are raised is even more puzzling

[Tom T.]

Actually, I had an old TR4 and one of the rear wheels was way out of balance--at 65 mph, but at 75 mph it essentially disappeared. Did get it fixed!

TT

[GEORGE ANDERSON]

I will assume they left the 428 externally balanced and you did use a 428 flywheel both times on the dyno. I'd see if you can get the balance card from the original shop that did the balance work and check the bob weight against another typical bob weight on another 428....this is the first step I'd take to be sure they did the math correct or at least find out if it's in the ball park...I'm sure we can find the correct weights for what ever combination you have....let's get that verified first......
The record should look something like this one...

http://www.gessford.com/images/balancecardcj.gif

if this is in the ball park then see if they balanced it with the clutch plate and if that's indexed for any reason because it wasn't perfectly neutral.....and running without it in this special case is causing a problem.
George

[xcobraj]

Thanks,George,

Engine builder was pulling the card for me monday i'll call him and get it

[427sharpe]

Ck the harmonic balancer--sounds like it has rotated out of spec, which means that the outer ring has shifted in relation to the inner one...with the motor off, see if you can make the two rings with some white paint ( a small line will do) and run the motor for a minute or two, than check and see if they have shifted. If not, see if you can get a hand on the outer ring and turn it by hand with a little effort...I doubt VERY seriously that a machine shops balancer was out of spec enough to cause this much imbalance!

[cobish]

what you need is a wobolator, that will sped up and slow down, just like on the ge turbines so that the 42 inch blades in the lp section do not resonated to destruction.

[SSSnake]

Cobish,

I didn't know there was anyone this close to me in PA. You have email.

Glenn Davis

[cobish]

sssnake
were are in pit?
i sent you an email. regards