Mopar Action On-line – Tech Questions
don Tackett, Virgie, KY, 1972 dodge charger, 400
I have a 400 dodge motor that has every thing it is newcam, lifters, everything. I have a bad miss and popping from the carb. Whatcould be my problem? I’m about ready to give up on it!
Don, 99% it’s a timing problem, valves or ignition.
Since this is all well known, I’ll just briefly go over the concepts. First,check the accuracy of the TDC mark using the “positive stop” method. Then besure the ignition timing is set to around 30-35 deg. BTDC, at 3,000 RPM,with the vacuum advance temporarily disconencted. And be sure the plug wiresare connected correctly – in the correct order!
If this doesn’t fix it, it’s a valve timing problem. If the cam isnear-stock, you can use the service manual procedure to check it. But, sincethis is really the only other likely possibility, just pull apart the frontof the engine and check to see that the timing marks on the cam and cranksprockets are correctly lined up. Aslo, be sure that the locating pin hasnot broken off the camshaft….remember, it’s only bolt torque that keepsthe sprocket correctly positioned to the cam. If the bolt isn’t torqued tospecs, the sprocket will snap the pin in a second and destroy the cam /crank timing relationship.