flatout

Ok new wires and checked all the plugs they seem fine. I pulled the wires off while it was running (got zapped a couple times). it seems to compoung the miss on every cylinder. No conclusive answer by pulling them off. # 8 was the only one that just barely changed. I did however find a bad vacuum line. the one going from the carb to the bottom of the fuel pump. Its a clear plastic looks like it was melted in one spot then broken after it hardened has a decent hole on it. Could that be the cause?

SB

iTrader: (1)

You have the fuel pump vent hooked to a vacuum port on the carb ?

Uh, oh.

This is a major rigging mistake that many people do. The vent line from the fuel pump must go to a vent on the arrestor or carb - most carbs don't have this.

Vacuum being hooked to the fuel pump will seriously reduce fuel psi since this is in the psi setting spring area of pump.

Re route this properly and see what happens.

flatout

could be a vent port I assumed it was vacuum u are talking to a shade tree not an ASE. its on the side of the carb not the bottom they are the edelbrock 1410's. both are hooked up this way but only one has the popping.

boatman22

flatout... did you ever find your problem?

rumblfish1966

quit screwin around and change the COIL thats prolly it

clonme2day

Had identical problem with 502 mag, Thunderbolt ignition and wound up being module in distributer!

wrench01

You may want to check valve lift for each cylinder, and also valve installed height.

A worn exhaust valve cam lobe could allow pressurized gas back into the intake, especially at revs, producing a consistent popping.

Also, intake valves too tight could also do this, sometimes detonation or overloading can push the valve stem UP and make it open early, before the exhaust stroke is finished, not enough to roughen the idle much or affect the motor unloaded but enough under power to shove exhaust gases back into the intake at revs, making a rambling misfire that is severe and power limiting.

To check that condition, pull the valve covers and loosen the rockers, then use a straight edge and see if the tips of the valve stems are all the same height, they should be.

I'm not sure a valve readjustment can cure this condition if found, but it might.

flash32118

Check line voltage to ignition.....if alternator has a problem then you wont see 13.6 to the box which will cause the problem you describe

flatout

pretty sure its the cam. I have checked everything else. response I get from evey mechani I come accross flat cam is about 85% of the answer. just haven't pulled the thing apart. Have got her out this summer yet.

Airpacker

look for a broken valve spring before hauling out the cam.