I had installed a 57 distributor on my 312 two years ago. With it a Pertronix ( original) with the flame thrower coil 1.5 ohm.
New high performance wires were also installed. 15 degrees of advance on the crank at 500 rpm with vacuum advance disconnected.
Vacuum advance is working.

It has always had a misfire at around 1500 rpm, but it seemed to clear up above that.

Now the fun starts: I took out my toploader and installed a mustang GT 5 speed. upon completion the car had developed a bad misfire in the 1500 rpm range. When below that it appears OK and if you get past that point in rpm it also appears OK.
Thinking that maybe I cracked the distributor cap. Replaced it and the rotor. Checked all of the plug wires. Installed new plugs. Set the valves, did a compression check.

What am I missing? The intake has not been off the car. The dual 4V carbs have not been changed.
I am at a stand still.

Hope you all can shed some light on where I should look next. I have not checked the engine to firewall ground strap. I have also not checked the internal distributor ground wire.

Jim

  Jim Rowe Elkhorn, NE