Had a clacking sound on my 1997 GMC k-1500 5.7 liter. Took off the valve cover and readjusted the lifter. Back off until it clacks-turn slowly until it stops clacking then go another 3/4 of a turn. Thought everything was fine until I took a little trip. I was running on 7 cylinders by the time I got back home. Soooo, I have two thoughts here, bad lifter or flat spot on the Cam. Your thoughts?

Easy to check, really... pull off the rocker cover and shoot a light down the rod journal...

If I was a betting man, cam... I know GM had some issues with cams back in then...

Is that a roller motor?
There's a couple of things I suggest looking at.
The rocker arm adjusting nut can/do lose their tension and can back off just enough for a loose adjustment.
And just possibly the rocker arm stud that's pressed into the head can be "pulling" out, not as common but does happen.

Joel

Thanks I appreciate your help. I did notice that the thread count on the rocker arm adjusting nut was less than the others. Has about two threads down from the top and the others were 5-6. Hmmm, a starting point.

Well now it's been along while so I thought I would close this out. I ended up taking off the lower intake manifold and I found the intake lifter on #2 cylinder laying around in the intake plenum. It was like it had just exploded. I bought and installed all new lifters and the Truck ran awesome for about a week then I started getting a hesitation or bucking at certain RPM's. If I pushed down on the accelerator it will smooth out.

After researching this I found out this appears to be a common problem so the "fixes" run the gamut from plugs and wires to removing and replacing the intake manifold gasket (again).

I decided to start with the distributor since one of the screws holding down the cap stripped out AND the distributor has 260,000 miles on it. Did that now I'm getting a P1345 code Crankshaft/Camshaft position misalignment. AAARRRGGG. Anyone have any ideas? I repositioned the distributor hoping that would make a difference but alas. There are no timing settings given for this vehicle instead it says the computer does it automatically.

It revs nice so I don't think I'm a tooth off.....Thanks in advance.

There has to be some kind of static setting/alignment setting for the distributor. Did you remove the distributor from the engine?

Any idea why or how that lifter was out of place? That would be my first concern. It takes a lot of something moving for that to happen.

Joel

you have the tools to measure the lift while rotating the crank by hand?

I think you might be expecting too much out of a 260,000 mile motor.

Yea, I took the distributor completely out, marked it up (rotor position, cap position etc), put the new dist in and it fell in exactly where the old one was position wise. I did measure lift on all cylinders (intake & exhaust). Once it was started I readjusted all. Runs great, sounds great but still has the Crankshaft Position Sensor code. You may be right, is does still have 260,000 miles on it. Time for a new truck, like the new Jeep J12.

Responded to your other thread as well....from reading online, your timing chain may be stretched. This can cause the valve to contact the piston, which I'm assuming could have also damaged the lifter. It can also throw your P code.

Thanks for the input. Didn't even think to look at timing chain. Must be gettin old.....