I would start by checking the timing. Timing that is retarded will backfire when slowing down.
Make sure the point dwell is set to 30 degrees. Then remove the hose from the vacuum advance on the distributor and set to timing to 12 before top dead center. Then attach the vacuum line and the timing should go up even more.
A baffle will not stop the backfire. It will suppress it.
Tuesday, July 7th, 2020 AT 10:37 AM