To get a better idea of the problem more info is needed.
Does it backfire under load, if so when hot or cold.
Is it back firing through the intake or exhaust?
Did you put points in and eliminate the electronic ignition?
What do the plugs look like?
What does your vacuum gauge read.
If you have an 02 sensor with a fuel/air mixture what does that read.
Did this occur after any changes?
Any other symptoms, hunting or surging idle, hard starting,
75 TR6 SC
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