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Helping someone with valvetrain problems

GM Guy

GM Guy

Manual Trans. 2WD Enthusiast
Messages
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Location
NW Kansas and SC Idaho
Hey all,

on another forum, this one agriculture related, a guy needs help on a 6.5L.

Quoted from his post:


"Yes, I know. Let it die but someone asked me to fix this engine. It was misfiring and I was told it was in the valve train. Valve covers off and all the rockers are loose, up to .180" lash. It had oil pressure so I assume it wasn't collapsed lifters. I don't know what the last guy did when working on it but would anyone out there have an idea which wrong parts he might have put in it? Push rods seem to measure out according to spec.
Cam. Lifters. Push rods. Rockers. Valves."

any more experienced help appreciated,
Thanks!
 
While they are there check for broken springs and then pushrods installed upside down causing extreme wear. Spin the engine looking for a flat cam lobe. Lifters collapse without oil pressure esp when holding a valve open. Otherwise START DIAGNOSTICS OVER! Because all the misfire told us was there is a problem followed by random guess as they really have no clue as to what's wrong.

Injector age? Now is the time change those as you have the valve covers off. Check compression. Check glow plugs. Check for air in the fuel system. PMD? Lift Pump/OPS? Fuel condition? Air filter? Grounds? HB condition? How many miles in regards to stretched timing chain and timing issues. Pressure test cooling system looking for blown HG or cracks.

This line of thought is really biased off the fact the engine is half torn down. Need to put it back together and diagnose it.
 
Don't know how common it is but I did come across it twice . The one kicked out the pushrod and bent it . Pulled the lifter out and it was flat spotted . Just remember you have preload in the lifters so your clearance is probably closer to a 1/4 inch . One of the signs in a roller is increased lash and that means rollers are bad or flat spotting .
 
How many miles, what kind of care, and how hard was it worked? Last misfire shot camshaft I ran across was this: http://www.thetruckstop.us/forum/threads/2000-3-9-dodge-v6-misfire.44482/

It's not uncommon and the flat tappet Cummins suffer as well. Roller lifters have reduced camshaft failures. Esp. with the engine oil changes.

Again I feel diagnostics should start completely over after inspecting everything that's torn down. Forget the valve train and focus on why it was misfiring. Burned valve, glow plug stuck in valve, hole in piston, bad glow plug, bad injector, blown head gasket, busted rod, air in fuel... A compression test would give a direction to go.

If he insists on checking the cam measure the movement of each rocker as the engine is spun over.
 
Before reassembling like WW mentioned, what do the rocker arms look like?

Is the .180 across the board or just 1 valve?

No manual I have read anywhere has you pulling apart so much if the engine before a compression test, did he just not know this or do we not have numbers to work on.

Injector misfire is more likely than a valve that has .180 lash. Did he ID which cylinder is the culprit and swap that injector with an adjacent injector to verify it is the cylinder instead of the injector?

Have him come on here where we can ask/ answer questions maybe?
 
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