[jciwolf]

My '70 GTO 400 with 4bbl Holley carb and HEI ignition runs fine in idle and at 30/40 mph. However when I press the pedal a little more or punch it, I get loud banging on the left side. It almost sounds like a misfire and then the cylinder fires again with all the other fuel still in it and creates the bang. How do I find the cylinder in question without running the motor and pulling the plug wire one at a time? The wires are ok and the plugs are not fouled or full of carbon.

I would also like to thank all who have replied to my previous posts and not gotten back to them for their kindness. This site is great and so are the members. Thank You All....jciwolf

[pggto]

Sorry I can't help you, but I might suggest you post this topic in the "Street Section" you will get a larger PY member base than just in the 70-72 group. Not that someone here can't help you.

How is the HEI wired? If your running from the original wire harness then you have the resistor wire to deal with and your not running on the correct voltage. HEI needs full 12 volts.

Did you inspect the inside of you dist cap and rotor? How old are your plug wires? Did you try a new set of plugs? It may not be a rich misfire, maybe its to lean?

[jciwolf]

Pggto Thanks for the reply. Plugs and wires new and rotor cap and rotor clean. Going to use a timing light to see if any particular cylinder is guilty. I know it’s not what it’s for but I figure if I ignore the actual timing and see if I do find a guilty party then I’ll claim success up to that point.