Resonating vibration

oldirish said
This is what I know, I bought the Duster with the engine/ transmission out of the car.

The heads on the engine were built at a machine shop in Albany Ga where I bought the car.

I don't have any specs on the engine. I was told that it had a mild Comp cam in it.

Once the car was assembled it cranked right up, had a little valve clatter but that is mostly gone.

It has the Sniper2 EFI and Hyperspark ignition.

I believe all 360 magnums are externally balanced from the factory so I'm going to be checking the damper and flex plates to start.

I'm also going to have the sniper checked out because I've read some comments about it causing vibration.

I'm fairly certain it's engine related since it vibrates in neutral at idle and higher rpm's

So, are you saying it's 5.9 with a stock bottom end, no mods?
If so, put a stock 5.9 Magnum flex plate in it, make sure the aftermarket balancer has the 5.9 weight on it, and you should be good to go.
And no, Magnum and LA 360s are completely different, although both are externally balanced it is still a different balance. The dampers do NOT interchange.