flywheel ballancing with 360 crate motor?
I recently bought a 68 cuda with a 360 crate, passon 4spd, when you get to 65 and up the veiw in the mirrors get so bad that it's like looking out the window of the Enterprise when it hits warp speed.
the vibration is not in the steering wheel but seems to surround you.
So I was thinking that maybe the flywheel was an neutral ballance, but not sure what that would feel like as I have never done a mix up like that.
There is a growly kind of deep vib from when ever but real bad above 65.
So before I go out and start looking it over I wanted to know what flywheel I am looking for?
The car does need just about every suspension bushing you can think of and I am sure it will need drive line bushings, other then that everything else is new in the drive line.
I have reballanced the wheels and repacked the front wheel bearings.

I would think that if the flywheel was out of balance, that it would shake if you rev it up in neutral. If it vibrates at speed and not in the steering wheel, then maybe a driveline or shocks. A tire can also do this. Look for a tire with a "bubble" in the tread. Just some ideas to start.

Is the driveshaft balanced? I would look there and it's relatively easy and not too much $$$.

Any idea what the Flywheel came out of? The Magnum 360 Flywheel is different from the LA. It is identified in the MP Parts Catalog (which might still be online)

Had a problem like that with my GTX and it was the driveshaft.

if you have the car at rest in neutral and bring the revs up to the same RPM as you feel the vibration at 65mph, then it's in the flywheel/crank. otherwise it's somewhere else, either a tire balance/runout problem, pinion angle problem, or bent/out of balance driveshaft.

Thanks for the replies, This was the second time driving the car, we got a real nice break in the weather so I went out for a cruise. The first time I drove the car was last fall from Niagara Falls to Toronto after it was shipped from Cali.
On that trip it was awfull, the car went straight to the shop, did a complete look over and thats where I found it needed all the bushings I mentioned.
The engine is fairly new, and I was told by PO that it was about 8000 miles, trans is even newer maybe 2000 it's from passon and still very stiff, and the diff from Mancini, along with drive shaft.
I have reballanced the wheels, etc..
What I am looking for from you guys is the difference of a 360 magnum and a 360 LA.
I know what to look for on a LA but not on a Magnum if there is one, I think you guys get what I am saying.
Thanks.
Maybe I should have ask whats the diff between an LA and magnum in the ballance?

there is a difference in external balance factor between the LA and mag 360, not sure of the exact amount. cranks are the same, but the mag has lighter rods, pistons, and ring pack which accounts for the difference. but if you put it in neutral with the car stopped, and rev the engine to the RPM points you feel the vibration at on the road, and it DOESN'T vibrate, then you can rule out anything ahead of the tranny, including the balance of the flywheel. it's a cheap test to prevent spending a lot of time and $$ on something that's not the problem.

If there is a diff I was thinking that it might be one of the many things that need looking at on this car.
Just checking the curiosity.
If its nice tomorrow I will get it out of it's slumber.

5.9 Mag is less than the 360 so the holes will be smaller in the back of the wheel. 318/5.2 Mag are neutral balance so shouldn't have the holes at all.
R.
What holes? Check out the MP diagram floating around.

Thanks.