I just spent $3500 having my 401 nailhead rebuilt with a complete kit from Kanter. It starts up just fine, but I have lots of vibrating in the dash, console, even the seats. It does not have the power it used to have and it cuts out from a stopping point. I returned it to the mechanics, but they have no idea what it could be. PLEASE HELP!!!! Any suggestions as to what could be causing this is much appreciated. I have already brought it to another mechanic for a second opinion. All tune-up items are fine. He says its on the lower end. What could it be?

Lets look at this frame by frame. You bought the parts? Pros rebuilt it? Did the rebuild include a newrebuilt harmonic balancer? Who attached from the flywheel back? Who installed in car?New motor mounts? Was drivetrain aligned?Who tuned up? Who installed distributor? Teh mechanics shrugged their shoulders at your engine problem? And what did you say? How did you leave things with them?
And finally...
If engine ran smooth and strong before all this, what was the purpose of rebuild?

i had the same problem with my 63 401 and when the carb was rebuilt a rubber (instead of leather like the original) skirt around the accelerator pump was letter fuel pass by freely after a carb replacement it ran fine

The 401 is externally balanced,and if the flywheel was not installed properly, you will have a vibration like you are experiencing.

I had the engine rebuilt because it had 130k miles on it when the accelerator stuck and I got into a fender bender. Within a day or two I started hearing a metalic tapping sound internal. I bought a complete engine rebuild kit from Kanter, brought it to what seemed to be the most knowledgeable engine exchange business in the yellow pages. After 4 weeks I get it back minus the metallic tapping sound and vibrating. Also, my exhaust isn't correct. I drove it for about 20 miles and returned it. No surprise from the mechanic. For the two days I had it, I brought it to a different mechanic who checked the dwelling in the distributor, adjusted it and told me that his best opinion is that something is out of balance. The harmonic balancer is the same, but I had no problem like this before when I brought it in. It started just fine,..no vibration,...just a tapping sound. Hope that is a better description, please continue with comments or suggestions. Thanks, Dave

PROPS TO THE OLD GUY!!!! You Rock! fly wheel was not correctly aligned. My ride home from the shop was a $3500.00 ride! Thank you!, Dave

I am glad to hear that the problem was solved. I know how you feel when you dump a ton of money ,and things do not go right. You can now enjoy your Buick for a LONG time,as those engines seem to run forever

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Joe T
37Buick coupe /455 powered
40 Super convert
57special on 72 Electra chassis
72 GS455 convert 13.0/105
63 225 2dr Hard top 25K original miles