Backfiring?

[JOZW30]

Recently completed the rear posi gear swap (2.73:1 to 3.73:1) in my 72 W30 4 speed & everything seems great mechanically.

I have about 150 miles on it and am trying to be gentle until it's had some time to break in. But on the couple of "hard pulls" I've tried, I have noticed that with the revs high, and the clutch engaged (first to second shift), I am getting what I think is a slight backfire or popping.

This never happened before the gear change. Do I have to adjust my timing now? What exactly is the cause?

Am I just over-revving now and need to get used to the new set up?

And, is this harmful to the engine?

Thanks!

Joe

[Plowman]

Sounds like you have a bad plug wire. Good luck. Paul

[Verne_Frantz]

Joe,
If that's the only change you know of to the car, I have a hunch that since your RPMs are climbing at a much higher rate than before that you might be experiencing point bounce. It's also possible that you're just revving higher than you're used to (by accident) which is producing the same effect. The first thing I'd try is a fresh set of points.

Flogging a car in the Spring..... Geeeze, these kids today........

[Salvatore]

Recheck your dwell. Go over the plugs and wires too. Maybe it is just valve spring float or carb tuning. Have fun!