back fire thru carb on 383

[Cudadrag]

I was over helping a friend with a 383 build. He has a new cam from mopar perf (Nothing big. I didnt see the exact numbers but just a replacement purple grind with hydrolic lifters.) and a new timing chain. The motor back fires thru the carb as if a stuck intake valve, but rockers move as if there is nothing wrong. What was a little odd was the new timing chain did not match up dots at 6:00 cam to 12:00 crank, but did match up 12:00 and 12:00.

I of course did not see disassemble so just a dumbass helper at this point. But still puzzled. I'm hoping he didn't get a bad valve job. Anyways I thought I would throw this out here if anyone wishes to shine their 2 cents worth. The timing chain deal does seem strange but does seem to work. When number 1 is up both valves closed number 3 intake valve is open thus should be on #1 fire stroke. Distrib appears to be in the correct position for spark to the appropriate wire.

As I mentioned it sucks walking up to someone elses assembly, but still puzzled. If you have a thought please share.

[John Kunkel]

At what throttle setting is it backfiring? Steady throttle or when flooring the throttle?

[te.ringer]

put engine @2000 idle,pull off each plug wire at cap until back fire stops ,could be bent intake valve too much lifter preload,wiped exhaust lobe on cam on that cylinder also check for cracked dist cap between term.
a big problem in my area is putting point dist.caps (lower quality) and rotors on electronic ign.cars they crack quick at 45000kv.

[chirorod]

I'm confused. Are you talking about dots on the chain or on the sprockets?

[cudabob496]

timing way off, too advanced
distributor 180 degree out?

[Cudadrag]

Found problem He had the distributor gearclocked 2 teeth advanced. (MSD dist.) Strange how it looked close but once we moved back 1 tooth it ran better. 2 teeth ran as should.

[340_GTS]

Who cares how the distributor is "gearclocked" (lined up)? You can have #1 pointing in any direction you want. The timing (checked with a timing light) is what matters.