Can a problematic Pertronix ignition module cause a misfire? I was driving my 69 XR 7, 351W (Newly rebuilt) yesterday and it was idling and running roughly.
My grandkids enjoyed the ride.
Any number of things can cause a misfire. I don’t have a Petronix unit on my car but I did have an MSD coil fail that caused a mid-fire after it got hot. Fine when cold but horrible misfire when it got hot or wet. New coil fixed the problem for me.
Thanks. I was thinking it could possibly be the coil.
There are many ways a Pertronix can fail. A misfire is one of those ways. Personally I think they are more trouble than they are worth.
If it misfires at idle and you are powering it off the coil then you have an easy fix. You need to run a 12 volt supply to the Pertronix. This can be done by installing a relay
When I first installed it many years ago I had it connected to the + terminal on the coil and had problems. It has been connected to a proper power source ever since.
Misfires can be caused by insufficient ignition, excessively rich or lean mixtures, or compression problems. In vehicles this old, I would start with a temperature gun on the manifold to determine if a specific cylinder is cold as any misfire will cool the manifold. After you determine a cylinder, pull the plugs and check and compare by reading the plugs. There’s all kinds of online help for that including the people in this space.
With a newly rebuilt engine I’d be concerned with a camshaft lobe going away etc. if you have a flat tappet cam and didn’t use an oil with zddp.