Cylinder not firing

[CrewCabMan]

Hey guys I have a 84 K10 that the #8 cylinder is not firing.Well it is actually firing but I dont think the cylinder is getting fuel.When I start the truck all the header pipes on each cylinder get hot except #8 .I have changed plugs,plug wires,checked to see if it is getting fire and it is.checked compression on that cyl it was 145psi.Friend said it was carb (edelbrock 750 manual choke) so put on a edelbrock 750 electric choke on it ,started it up and #8 header pipe got hot but i could not get it to idle right. So got can of carb cleaner and cleaned up manual choke 750 put back on same problem.Put electric choke 750 back on and now #8 is not getting hot again. I assume since it has good compression and is getting fire it is a fuel problem,but not sure where to go from here .Please help

[Dan1969]

Hmm, clean your intake as well...??? Does it idle rough?

[BMERDOC]

Can't be the carb. It is centrally located and feeds all cylinders. How do you its getting fire? Did you pull the cap and check inside? I'm thinkin and I'll get back if someone doesn't find it for you first.

[BMERDOC]

Has the truck been sitting. Can you pull the carb again and check for a mouse nest in the runner? That is if it has been sitting. How about a sticking intake valve?

[youwish2bme]

Originally Posted by BMERDOC

Has the truck been sitting. Can you pull the carb again and check for a mouse nest in the runner? That is if it has been sitting. How about a sticking intake valve?

I'm going with door number two.. Intake spring broken or valve stuck.

Dave

[CrewCabMan]

no i have not cleaned the intake. it does idle fine.i have started to pull the valve cover and look around but i have not got that far yet.when you rev the motor it does pop some thru the carb

[BMERDOC]

POPPIN THROUGH THE CARB!! We've been here before. Pull that cover and check the intake valve and associated valve train.

[CrewCabMan]

also the truck has a fuel cell in the bed because the gas tank had a hole rusted in it so i just stuck a fuel cell in it but he seal around the lid must be bad because i got water in the fuel cell.the truck ran great before this happened.so i drained all the fuel blew out fuel line and changed the filter and have had this problem every since then could that have anything to do with it.

[BMERDOC]

Read this 72Tealnwhite had a similar experience.
http://67-72chevytrucks.com/vboard/s...d.php?t=471111

[CrewCabMan]

well i pulled the valve cover off and it looks like the pushrod is bent on the exhaust valve.when it is running it looks like the pushrod is wobbling around. what could have caused this to happen?

[notyo_cheez]

Originally Posted by CrewCabMan

well i pulled the valve cover off and it looks like the pushrod is bent on the exhaust valve.when it is running it looks like the pushrod is wobbling around. what could have caused this to happen?

As suggested, if you hot tank the head you may damage the valve guides. Don't short cut engine repairs this way. Usually a push rod bends if it's been overheated or poor quality, or rocker arm sticks, or misfiring or the valve contacted the piston, etc...

The long block assembly is a precision machine, and when all is in harmony the engine wears evenly as it's been running. Depending on the age of the engine you may want to consider a rebuild. A reconditioned head will mean an increase in compression for the cylinders on that side, and the rings may not like it and tell you so by blowing by.

[wyattglock]

A stuck valve, carbon buildup in the chamber, soft pushrod (not likely). I would pull the heads and have them hot tanked and magnafluxed. That can usually be done for less than $75 bucks.

[BMERDOC]

Don't forget to let us know how you fix it!!

[CrewCabMan]

the motor in the truck was built about 10 years ago and probably only has about 7500 miles on it .It has never been abused or overheated and was built with quality parts. brand new 4 bolt main block from scoggins dickey,brand new world products sportsman cylinder heads,speed pro forged pistons, comp cams cam,lifters,pushrods,roller rockers only thing not brand new was crank and connecting rods.I am having a hard time swallowing the pill as to why this has happened

[CrewCabMan]

well i pulled pushrod and it is not bent ,put it back in adjusted valve,started truck and noticed the intake valve on #6 was barely moving ,#8 intake valve was moving a little more than #6 and #8 exhaust valve is barely moving so i am now thinking camshaft has gone bad. i dont think it is lifters collapsed because they are not making any noise.

[Your41Plague12]

If the cam wasn't broken in properly when the engine was rebuilt, you could have unevenly worn down the cam lobes. I'm betting that's what happened if your symptoms are as you describe. That's why I became weary of buying someone else's project. I've had both good and bad luck with it.

[pumpgas]

I would point my finger at the 7500 miles in 10 years of use as the problem. That would leave plenty of time between uses to allow the oil to drain off the cam and bleed off the lifters and cause uneven wear on the cam lobes.

[k10shortbox]

i agree with the cam, i had a comp that only had about 500 miles on it when it started missing. pulled the cam out sure enough one lobe was completely ground off, comp said it was a bad grind...

[BMERDOC]

I agree with them. Probrably started with improper break in from the builder.