spin289

Alright, I'm looking for some good info about what might be happening with my engine. Ever since I had it rebuilt it has a bad vibration in it at all RPM's. Here's what it is: 289, .040 over, H-beams, KB pop-ups, E-brock RPM Heads/Intake/Cam, Holley 650 DP, MSD 6A and distributor. I had all the work done at a pretty good machine shop, bored, balanced, etc..... It was really bad and I noticed one of my plugs was jumping spark. Replaced it with a new one and it helped the vibration but didn't cure it. Can anyone tell me what is a good plug to run with the Performer RPM heads? I am running Motorcraft 32C's but would like to go to a better plug. My taurus SHO runs motorcraft 32PP's platinums. Will these work? Any other ideas trying to track down a possible miss in the motor. Also can anyone tell me what carburetor jets to use with my combo? When I gas it the engine cuts out for a second and then revs. Thanks!

Chopper

If it idles well enogh to run this test you can track down a possible miss.Remove plug wires one at a time untill you either go through all of them or you get to one that doesn't change the idle when it's removed.This will be the bad cylinder.Be sure to check the firing order also.A lifter might not be pumping up and making a cylinder weak.If you have headers you can use a handheld pyrometer to look for a cold(or cooler) header tube.If the carburetor has an adjustable accelerator pump try giving it a bigger shot of fuel to help the lagging engine.