Re: Poping 258 engine Any suggestions

[farna@xxxxxxx]

Either the intake valve is burned or sticking open. When the cylinder fires the explosion is "leaking" into the intake and out through the carb. Pull the valve cover and make sure the valve is closing all the way. The pushrod could be out of the socket on the rocker or lifter, but more likely the valve is burned or cracked. I've had cars that sat for a while and the valves started sticking. Spray some penetrating oil (WD-40, PB Blaster, etc.) around the valve stem and strike the top of the valve several times with a hard rubber/plastic/wood hammer, or use a block of wood and steel hammer. That will loosen the valve. It sticks in the lifter due to carbon and varnish from firing and dirty oil. After running a bit it may stick again. I had to pull the valve cover and free mine a couple times before it ran right. Should have used an engine flush when I changed the oil shortly after. Might not have eliminated a repeat, but I think it would have -- certainly wouldn't have hurt! Lu!
 ckily this was a 196 with only two valve cover screws and a rubber gasket.

On July 18, 2005 Bryan Morrow wrote:

> 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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