The Stovebolt Site Forums The Parking Lot Big Bolts The 48 2 ton is baaaack

The owner is using it as almost a daily driver. Loves to take it to his company's work sites and move equipment from place to place. Saw it with a 4000 lb lawnmower on the bed and the receiver hitch has a pintle hitch in it.
Got a call late Saturday that it had a problem. Running rough, no power, lots of noise, wouldn't idle.
bottom line, it had dropped #4 intake valve.
Trailered it down today and confirmed o compression in 4, removed valve cover and found the spring, retainer, etc laying on the head and the valve banging up and down on top of the piston.
Have no idea what caused it. All of the parts are a bit banged up and the pushrod has fallen down in the side cover. The valve guide is wiped out.
The odd part (more odd than that) is that the timing (at least ignition but possibly cam) is retarded.
I tied a wire around the valve stem (not bent) and tied it into the closed position, took the spark wire off and ran the engine. Instead of running like an engine with a miss, it ran badly and sounded very retarded.
More tomorrow.

Well that's a shame. I wonder what made it come apart?

Got the head off. Had to take care of another project to make room to bring the 2 ton in.
Never seen one like this before.
The valve face is broken basically in half.
The groove for the keepers looks like the valve was pulled through the keepers.
The piston top has a polished circle from the valve bouncing off of it. The broken part of the valve was just bouncing around in the cylinder.
No damage to the piston, cylinder or combustion chamber, or pushrod.

Curiouser and coriouser!!

Will take the head to the shop tomorrow. Have the guide replaced, seat dresses and new valve installed.
Will check out the timing while it's gone.

Got the head back from the engine shop.
Replaced everything for the #4 intake and pulled all the valves, inspected everything and found nothing else wrong.

Still no idea why it failed.

Got it back so soon I'm stuck because won't have new gaskets until Monday.

Huh, not knowing the cause of a failure tends to leave me lacking those warm fuzzy feelings. Hopefully it doesn't happen again.

The head is back on and it runs really badly!
I'm posting details to the Engine forum, really strange.
Need the best brains in the realm to help on this one.

Still not finding an answer.

Have you tried a leak-down test instead of just a compression test? I do find them to be a bit more informative. I like to check each cylinder at multiple points along its power stroke just to be sure.

In case you weren't following the thread in Engines, it was the ancient NOS manifold gaskets I got with the head gasket that were porous and not sealing.
After a lot of waisted time, purring along.

By the way, another red herring was the temp gauge. New when I rebuilt the gauge cluster.
It appeared that the engine was suddenly running hotter as well.
Turns out the gauge has gon out of calibration.
Engine used to read 170 in normal running, suddenly it was 185.
Turns out it doesn't return to 0. Today the shop was 75 in the morning and the cold engine was reading about 120.
More reproduction part junk? Don't think I've ever seen a waxstat do that before.

The 2 ton is ready to leave again.
A little work on balancing the carbs after being on and off a few times and a couple adjustments to the timing. Took it up on the interstate a couple of times and the tuning is in the sweet spot.
So nice when she is cruising 65-70 and holding it on average hills.