Spark Jumping through wires to firewall

Anyone got a better idea?? Here's my scenerio. I just installed a Weiland dual Quad tunnel ram, on my 57 Chevy wagon.. For the Dist. I used a Vertex Magneto.
Before this swap I had an edlebrock performer intake and singe 4bbl carb on there with a HEI dizzy.... never seemed to notice a the problem before.

When I rev the motor up I can actuall see sparks traveling through the insulation on the wires going to the firewall..... For the time being I placed some tar paper :3dSMILE: along the firewall to see if that helps,, but I do notice that while drivng down the road the car sounds "muffled" then without increasing the throttle or slowing down at all it "perks" up and acutally sounds like it is now running on all cylinders... Kind of hard to explain other than that, but I am guessing that it is shorting out some of the wires before the spark get's to the plugs.... I checked all the wires for cracks or breaks and they seem fine,,, although Really close to the firewall...

Perhaps the deficiant insulation is not visibly evident.

You could quickly splice a new piece of wire through the firewall area only and see if it stops.

If it does - replace the entire wire.

Bert

Try looking at the thing tonight in the dark. You should see a light show.

We acutally got it back together last Saturday night and fired it off outside in the dark... your right,,, pretty cool light show :rolleyes:

If more than one wire has bad insulation, the voltage could jump across wires rather than to the grounded firewall only.

So the 'tar paper' :D might not isolate the problem.

Bert

It does currently have the 8.5 wires on it.. They were new last year when I had them in my Model T... Since sold the T, and kept the heart of it....

And what about plug gap, most of the sprinters & midgets iv'e delt with run Vertex's and they only gap the plugs .012 to .019....... If you still got the plugs at .060 for the HEI thats a hell of a bridge to jump...... But still I think Denny's on the right track with bad plug wires....