I put my internally balanced 396 in and am getting a bad vibration above 3k rpms. I reinstalled my sleel flywheeled mcleod twin disk(from my previously stock 350) on the 396 . I was told, not by the engine builder(comb. motorsports), but by my mechanic that it needed to be neutrally balanced because the stock 350 was externally balanced at the rear. I have put 700 miles on it so far. Can this have damaged my bearings already. Should Combination have told me about it since I told them I would be using the mcleod flywheel from my previous setup?

Thanks, Aaron

 

I had the same problem with my 396 internaly balence A4 set up.
I bought the internals used, and assembled it. I had a horrible vibration at 1200-1600 rpm. The previous owner must have used a neutral balenced flywheel with his set up. I removed the flywheel and had it balenced neutral, now it's perfectly smooth.
As far as any damage, I only ran the motor for 15 minutes before I figured out my problem, 700 miles is alot, how is your oil pressure, anything unusual in your oil?

Good luck
Brian

 

My oil pressure has been very consistent and in the normal range.

 

I have a similar situation. 396 internally balanced. I bought a street twin and removed the weight from the flywheel to make it neutrally balanced. I had a vibration, and now it sounds like I have a bearing going. I'm right around 800 miles on the new clutch. I think if I had left the weight on everything would be ok, but of course I didn't keep the weight. I'd get it checked out now. Hope that helps.
Malcolm