It could be a couple of things. Check your ignition wire placement - two plug wires crossed could do it - one cylinder not firing at all, the other one spitting up through the carb. cross-fire from bad wires arcing between each other could do it also.
It may be a flat exhaust valve cam lobe. Pull the valve cover and take a look there - could be a bent push rod too. I had one do that and it turned out to be two bent push rods on one cylinder, a broken guide plate (not a factor in your case) and both rockers off of the stems slightly. The exhaust worse than the intake. The engine was quiet but popped through the carb.
Pull the valve cover and take a look.
Old Champion plugs can do stange things too.
Hope that this helps some!
Bill Dettman
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Subject: Poping 258 engine Any suggestions
Date: Sun, 17 Jul 2005 23:46:34 -0600
I have an 81 Concord. 258 auto air.
At Idle the car gives off a poping sound through the carb.
If I pull number 6 wire the poping goes stops.
If I put the wire back on and rev the engine the pop turns into a violent
bang through the carb.
I have changed plugs wire cap and rotor.
Adjusted timing. Compression is 145-150 across all cylinders.
It appears to be timing but I can't figure out whats left.
no matter where I put the distributor the pop is present.
With all 6 wires on the engine will idle.
As soon as you pop it in to gear the engine bangs and
stalls.
If I remove #6 wire I can put the car in gear and drive it.
Any Idea's.
I am stripping the car but want to make sure the engine runs well before
pulling.
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