Greetings
I am a newbie. I decided to have a mechanic add an Offy 5416 intake and a Holley 8007 4 barrel carburetoralong with HEI as a lot of forums recommended this setup. I am experiencing back fire on deceleration. Can anyone share their experience. The motor is stock. I appreciate any constructive comments.

Are you sure it is back firing? Could it be more of a exhaust rattle or rasping?

What is the timing settings?

Timing is probably too advance or you're running too lean. Check the timing first.

I will ask them to check the timing thanks.

Running to lean?

Meaning not enough fuel being dumped through the carb. Lean or too advanced will both give backfires.

How about you check the timing and tell us what it's at then pull a spark plug and take a picture of the sparky-end for us to see? Reading spark plugs is an art that many have lost.

Thanks for the great advice. I will try to do it this weekend and a will post the result. I appreciate the guidance.