Engine is back firing through the exhaust

Tiny
KOOLKATPREZ
  • MEMBER
  • 1961 CHEVROLET TRUCK
  • 60 MILES
1957 Chevy 283 with all new ignition components backfired thru exhaust prior to change and also after. What could be the cause? Replaced plugs, rotor, cap, condenser, plug wires. Engine ran great on an 8 mile drive then started backfiring and missing on the way back home after being shut off for about 40 minutes.
It is backfiring through the exhaust, I've replaced all ignition components and checked timing several times in search of the problem.
Wednesday, October 12th, 2011 AT 9:31 PM

2 Replies

Tiny
RIVERMIKERAT
  • MECHANIC
  • 6,110 POSTS
Timing too far retarded. Timing chain slipped. Bent exhaust valve.
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Wednesday, October 12th, 2011 AT 9:46 PM
Tiny
RIVERMIKERAT
  • MECHANIC
  • 6,110 POSTS
Yeah. I almost lost my 74 Charger to a bent exhaust valve causing a backfire.

Moisture in the cap and wires can also cause backfiring. Check for a defective cap with tracing between the high tension terminals inside the cap.

A backfire through the exhaust can be caused by a few things, either alone or in combination:
1: Incorrect timing
2: Faulty/defective exhaust valve
3: Faulty or defective cap
4: Over-rich condition leaving unburnt fuel in the exhaust
5: Electrical problems causing the wrong plug to be fired. This could be caused by something like an intermittent open in the ground to the coil.
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Friday, October 17th, 2014 AT 7:40 AM

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