Technical 327 Pulsating Surging Vibration

Is that with the vacuum line disconnected and plugged? If not, it should be. You should read about 32-34 degrees at 3500 rpm with line disconnected and plugged.

The line should be connected to the connection closest to the manifold (manifold vacuum) for a SBC. That will increase your idle and partial throttle timing about 15-20 degrees. Vacuum sounds about right, so it doesn't seem like you have a leak and it sounds like your distributor is working correctly.

Do you think the engine is surging or there is some sort of driveline surge/vibration?

 

Sorry the vacuum to the distributor is connected to the carburetor.

Thanks for your insite. I feel the vibration surge not the RPMs Car sitting still in neutral. I was thinking of a imbalanced flywheel or clutch.

Again thanks for your help.

 

Then, you could also possibly have a harmonic balancer that has slipped. The only way to check it is with a piston stop and you need to be able to rotate the engine by hand.

Good luck!

 

I'm also thinking a damaged harmonic balancer. I use new ones on fresh rebuilds. It may run true and not wobble. Simple checks, engine and transmission mounts, exhaust hitting something. Was the clutch replaced? I like to have the clutch cover balanced with the flywheel.

There was a thread on here, someone chasing a vibration and it was a bad pilot bushing. Is the shifter hitting the floor?

 

I was a vibration T/S expert for 10yr....seat and steering wheel was such a flashback... the std semi truck complaint. Guess where you hook the vibration transducer....Frame, Engine..CL of crankshaft.., Steering wheel, seat. Speed sweep capture data ...done.... could be anything from misfire, balance, mount durometer, mount shorted..metal to metal, damper, crank, flywheel, clutch, cam, ...driving or not....push in clutch...elim drive line.... if you got a buddy at a diesel repair OEM truck shop, Cat Dealer... they can tell you in no time. I used to train dealer techs as well.