Picked up a 1978 Trans am with a 400 in it. For some reason the previous owner put an old point type distributor in it, so I converted it back to the HEI. Put a new distributor, cap,rotor, coil, plugs and wires, now it keeps backfiring through the carburetor. The plugs are set at the right gap .045. I did install a new intake and carburetor because he also had to big of a carburetor and it was dumping way to much gas in the motor. Did a compression check and 3 of the cylinders were showing 80psi, the rest were at 100-110 psi . I was told that to much fuel could be the cause of low compression. Any reasons why it could be backfiring and is true about having to much gas in the cylinders
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