Say folks I just sold my 350/300 H.P. to a friend and he installed it in a 36 Chevy that had a 283 in it. We got it started fine and we went to a cruise in this past Saturday night and it ran fine. He called me over today and it is running rough at idle and at about 1500-2000 it will backfire (intermitting) through the tail pipes only not the carb. I have many backfire through carb but not out the back. WE put a brand new GM HEI Distributor, plugs, plug wires, man I am at a loss on this one. This is a sound 350 with only 5000 miles on it, not a clunker for sure. It seems to me it would have to be a firing problem, but what??? Any suggestions would be appreciated.

Thanks,

Jesse Robertson

What is the timing set at?

It could be a problem with moisture (or crack) in the distributor cap. Did you install that new HEI distributor before of after the backfiring started?

The timing is set at 12 BTDC, the spec sheet that came with the engine ask for 10 BTDC. Yes we installed the new cap/distributor prior to the first run. The one thing I do not like is his tack wire and hot wire from the ignition (going into the distributor)is just bare connectors (no plastic insulators around them), however this set did well with the ole 283 it seems. He had to go out of town today so we stopped working about noon. I am thinking it could have a cracked plug but why would it show up now. We pulled the cap also this morning looking for moisture or arking and saw none. Thanks guys all suggestions are appreciated.

Jesse