72 gmc 350

[tk1251k]

Valve lifter making pecking for quite sometime. Plug fouling out at bad lifter location.What is the best way to tell if cam lobe is bad or collapsed lifter, Tried to adjust lifter but could not tighten enough.thanks terry

[Sport/Truck]

I’m think you can tell with a dial indicator by checking how much it raises, & compares it to the others.
s/t

[tk1251k]

I dont think it moves much at all. Did a head job couple years ago on it. Plug totally fouls out one cylinder only where exhaust valve not working . I am not sure if cam lobe bad or one collapsed lifter. terry

[Sport/Truck]

Are the valve covers off now?
s/t

[tk1251k]

No.

[Sport/Truck]

I’m thinking the only way to tell for sure is to remove the cover and start it up and watch what is going on. If it’s not moving at all you’ll be able to see that. I’m thinking if the cam lobe is wiped, it won’t be moving as much as it should, and this is where you’ll need to measure the lift. Do you have a dial indicator?
s/t

[tk1251k]

No I do not have one .Any other way besides the obivous out removing.terry

[Sport/Truck]

not sure, (I'm thinking)

[special-K]

If it`s not moving the rocker at all,it`s probably the lifter.A bad lobe wouldn`t be that bad.It sounds like a visual inspection will determine that the rise of the pushrod is less.

[Sport/Truck]

If, it’s not opening at all, then a leak down tester could possible tell. (will hold pressure in the exhaust stroke) but I have doubts that it is not opening at all, just not opening as much would be my guess.
Did you make sure the plug wires are good allowing good spark to the plug?
Just wondering why you suspect it to be the cam.
s/t

[tk1251k]

When valve job was done the lifter in suspect could not be adjusted down.This is the same valve where plug fouls out. Pecking noise at start up then stops when hot. terry

[tk1251k]

Plug wire fine got plenty of fire to plug.terry

[Sport/Truck]

Originally Posted by tk1251k

When valve job was done the lifter in suspect could not be adjusted down.This is the same valve where plug fouls out. Pecking noise at start up then stops when hot. terry

This makes me believe it’s the lifter and not the cam.
Anyone else??
s/t

[tk1251k]

I think I will remove the intake and remove lifter . If the lifter is just seized is there any other remedy to try first . terry

[tk1251k]

Thanks sport-truck and special-k.

[tk1251k]

After looking at rocker movement I would say it is moving about half the others. terry

[Sport/Truck]

I think you can free it up using ATF. Not sure how to go about this with the lifter out though. I would check before I pulled the intake off. Because if it just a sticky lifter, you may be able to run some type of cleaner (I think ATF works) and fix the problem.
I would hate for you to do allot of unnecessary work for no reason. Try Google with sticking lifter and see what you find.
s/t

[Sport/Truck]

IMO this could go either way, but I’m thinking if it was the cam lobe, it wont go away when it’s warm.
Anyone else??
s/t

[tk1251k]

Thanks I will try that.

[tk1251k]

Seized lifter or bad lobe either woul cause plug to foul constantly wouldn t it?

[Sport/Truck]

Originally Posted by tk1251k

Seized lifter or bad lobe either woul cause plug to foul constantly wouldn t it?

I would think so, because it’s not opening all the way, therefore closing before it expels all the burnt gases. And progressively will get worse because the fresh intake mixture is mixed with the old exhaust.
What did you find with Google?
s/t