440 missfire
 

IM NEW TO THE SITE.
NEED HELP. I HAVE A 72 DUSTER WITH A 440 RB BLOCK.
ENGINE MISSIFRES EVER SINCE I BOUGHT THE CAR. OCCURS AT ABOUT 2800 RPMS OR APPROX 60 MPH. WHOLE CAR SHAKES AS IF WHEEL WAS OUT OF BALANCE OR BAD DRIVESHAFT. I REPLACED CARB FROM EDELBROK TO A HOLLEY 750 4 BBL. ENGINE DOES RUN RICH AND DID BEFORE CARB EXCHANGE. REPLACED PLUGS & WIRES,CAP & ROTOR. THOUGHT WAS DRIVESHAFT YEARS AGO AND HAD BALANCED. IS IT CARB MIXTURE,TIMING,VALVES. FUEL PRESSURE READS AT 6 LBS AT CARB.
ANY IDEAS
THANKS IN ADVANCE

thats not a misfire

duster -

Does it sound like a misfire or is it a vibration?

If the timing is correct, are you SURE all cylinders are firing?

Does it get worse when you turn the lights on?

Does it do it only when the car is moving, in neutral or both?

We can't hear/feel it from here, so the more specific, the better.

Archer

is the car able to rev higher than that rpm?

car runs great untill 2800 rpms. when stopped or driving. its definitly a missfire that feels like vibration at 60 mph.it will rev higher with no problems.

has nothing to do with lights,timing is correct. runs perfect up to 2800 rpms and beyond that its fine. i havent taken a compression test yet or played more with carb mixture.

dead cylinder

Do you have a cast crankshaft or forged? The harmonic balancers are different. The wrong one will cause alot of vibration, at certain RPMs it worse. If the whole car shakes, thats more than a mis-fire on a cylinder. And a dead cylinder shakes more at low speeds, then usually smooths out as it revs up. Plus one spark plug would be black or dark color.