[kdavies3]

Hi Guys, I know that I'm in danger of being lynched for having a Chevy 383 in my Cobra but it's quite common here in the UK.

Anyway I have a HEI dizzy in the motor which was supplied last year by the Engine Factory. I have a problem in that the ignition timing appears to have a mind of it's own.
With the base ignition set to 10 deg BTDC at idle vac disconnected and plugged, the engine runs OK until I rev it above 3000 rpm then It begins to misfire and backfire as though the timing has gone mad.
Also when I connect the vac advance up the engine cuts out almost immediately unless I give it throttle at which point again it misfires and backfires as if the ignition wires were crossed or the firing order was wrong. (it isn't)
The Carb is clean with no blocked jets etc. No air leaks etc.

Can anyone shed any light on the problem?
Or is the dizzy just toast?