Stuck valve??

[1980]

I think I have a valve thats stuck open. The motor started poping thru the carb. Like a backfire, but no flame seen. I started checking the plug wires and on the second one when disconnected the poping stops and the motor runs much smoother. I know I need to pull the valve cover to see whats going on, but its extremely cold outside right now so I'd prefer to wait a day or two. What damage would I do to drive it with a sparkplug wire disconnected?

79 GMC K1500 350

 

[bot0611]

Suscribed

 

[KansasTwister]

could be a burn valve, The last time i saw a valve stick was because of leaded gas built up on it and then sat for a long while, id have to ask dad how we loosened it up on his 65 chevelle malibu ss 327/4bbll car.

 

[sweetk30]

might be a flat cam. had a 454 1 time ran perfect till around 2500 rpm -up. then would pop up threw intake. pulled intake found 3-4 exaust lobs gone on cam. had just the right amount of lift for low rpm runnin. but no flow for upper rpm exaust to all get out.

 

[KansasTwister]

Sweetk30 you must be talking about an exhaustlobe? My 78 has an intake lobe going so I'm at the better of the two worst outcomes lol.

Dad said the carb and choke cleaner broke the lead down the best if that's your problem, but I'd check the cam first. The worst lead buildup was our 64 2.5 ton wrecker.

 

[1980]

Thanks, I want to wait a few days to work on it, so
What damage would I do to drive it with a sparkplug wire disconnected?

 

[diesel4me]

It will "gas wash" the cylinder,meaning the unburned fuel will wash off the oil and cause the rings to score the cylinder,and it might carbon up the cylinder too..

Marvel Mystery Oil will free up sticking valves better than most anything else--you can add a quart to the crankcase (provided there is room,dont overfill!),and put a small amount in the gas tank--it'll smoke some while its burning off,but if the valve is going to free up by itself,that is what will do it..."Seafoam" is good for that too,I prefer Marvel,its an oil,not solvents that might cause a problem...
You may have a bent pushrod or a rocker arm that broke or got stuck on a grooved rocker arm stud or something,or a valve spring may have broke too..

I had an engine with a flat cam lobe on an intake valve--it caused a lean mixture,you could see how hot the piston got,it was partly melted above the top ring groove all around one side!...the valve was barely opening,had about 1/8" of lift..

 

[Greg Ducato]

I'm guessing flat cam lobe, continued operation will just pump more fine metal into the oiling system and also mushroom that lifter making it a lot harder to get back up though the lifter bore when it comes time to remove it. I hope I'm wrong...