Stuck Valve?

[seventynine]

A little background: I have a ‘77 Cherokee Chief, 360 4 barrel, TH-400 with Quadratrack…all factory unmolested stock. It has 40k original miles. It ran perfectly in every way. I had rebuilt the AC system which ran great after. But…the rebuilt York AC compressor I put in crapped out a few months later. So I pulled the compressor sent it back and got a new one. My plan was to have it back together in a week. Well…life got in the way and the week turned in to 12 years ;~>

Recently I finally got around to putting it back together and back on the road. The fuel tank had begun leaking so I replaced it with a Poly tank. Also replaced all the fuel lines, fuel pump, filter etc. I rebuilt the carb as well.

I finished all of that up and was able to get it started but it ran terribly. Wouldn’t idle and was horribly rough. Today I swapped out the carb for a new one which didn’t improve the performance. I had it running roughly and suddenly heard a fluttering metallic clanking for a second or two. Then it stopped and like a switch it ran smoothly for a few seconds. Then it started clanking again and I think starting running roughly again. I shut it off at that point.

So…this motor has been sitting for a long time and maybe I’ve got a stuck or sticky valve or two? I know my next move is to pull the valve covers and take a look.

Any suggestions on how to diagnose this? Or other thoughts?

Thanks

[will e]

Compression test is a good next step.

Although your valve cover gaskets are probably shot anyways so my as well pull them.

[devildog80]

My '84 GW sat for 18 years, never pulled the valve covers or pan, and no leaks. Started up and would let run a little at a time, then rest a few days, then run it again until I was able to have it driveable. Now short store trips, and only about 10-15 miles in town still limbering it back into shape. Finding other little things popping up that need tended to, but engine feeling better every week, with each little run around town. Have had it out on interstate, but again, only about 15 mile turn around trips on test drive after repairs/adjustments, just to let everything get settled back into its place.
I would suggest you use some Berrymanns B12, Sea Foam, or Marvels Mystery Oil treatment in the engine oil, and do the short run times to get it mixed through the engine good, then shutdown and let it sit for a few days. Also start with a new filter. This will let the chemical treatment do its job, breaking down the sludge in the lifters and oil passages slowly, and not chunking off to plug anything more than it might be now. Plan for a few weeks, while you get other things done, and should free up the insides nicely without such invasive actions like opening up the valve covers just yet.
My engine was still in good shape, and did not require this treatment, but the 727 auto trans I did use the Berrymanns B12 treatment, and got it freed up nicely. Put the full 16 oz can treatment in and drove it for 2-300 miles over many small trips, then drained & replaced filter and pan gasket. Drives and shifts perfectly now, as it was a bit sluggish when first driving after sitting so long.

[letank]

clank and metallic sounds are hard to diagnose, but as wille said, you need a step by step approach. The valve cover removal would allow for a more complete observation of the valve train when you do the next step below.

using a wrench at the harmonic balancer to slowly rotate the crankshaft, it is easier if the spark plugs are removed, check the look of the spark plugs for damaged /bend electrodes, hopefully none!

can you freely rotate the crankshaft without feeling any resistance, spark plugs being out, rotate a few degrees back and forth and report, do not force the rotation.

If there is some resistance, the clank could be a dropped valve , if the engine stopped as you described above.

A fubar hydraulic lifter is usually noisy, a chewed up camshaft may only affect one or few valves!

A 1977 with 40K miles... it could be 140K miles... or more. My 74 display 49K miles... but it is 349K miles

[Harry Dawg]

You could hook a vacuum gauge up to it and see if it reads late valve timing.

As mentioned, pulling the valve covers and inspecting.

Check for bent pushrods. This may indicate a bad lifter, or resistance from the valves.

Not sure on the 360, but you may be able to pull the intake and look down the intake / exhaust runner and visually inspect the valve.

Sent from my Pixel 4a (5G) using Tapatalk

[seventynine]

Thanks for the suggestions guys.

I’m absolutely sure of the mileage being 40k. I bought it from a friend on IFSJA whom had bought it it new in ‘77. It had around 28k miles on it when I bought it 15 years or so ago.

I know the miles are not necessarily the key here…it’s the time sitting idle without having been properly fogged for a long sleep;~> it’s no good for any motor to sit a long time without running regardless. I can’t believe 12 years has gone by;-P

I had it running several times in this process up to operating temp. But…it ran real rough. It’s just interesting on the last run that it clanked for a second or two and then ran really smooth. It started clanking again a couple of seconds later and I just turned it off. I’ll add som Marvel Mystery Oil to the crankcase. I did add some Lucas fuel treatment to the fuel already. I’m pulling the valve covers tomorrow to take a look. I’ll keep you posted.

[seventynine]

Bad news…

I think I have a connecting rod problem. Number 5 piston is hitting the spark plug. See attached pic of the spark plug I just put in recently. I put a camera into the cylinder and the top of the piston is all gnarled.

The motor is locked up. I pulled all the plugs and can only turn it just less than a full turn either way. And it doesn’t move that easily even without the compression.

So I think the motor is toast without a rebuild.

Perfect.

[Srdayflyer]

take and old spark plug, break out the ceramic and weld or braze on an air chuck nipple bring each cylinder 1 by 1 to tdc install the modified plug apply 4-5 psi and check quite a few things. 1. ring bypass provided valves are tight air thru oil fill 2. intake valve bypass air coming out of carb 3. exhaust air out of tailpipe. 4 bubbles in radiator bad head gasket, you can get a differential compression tester (2 pressure guages attached with a manifold) you apply 80 psi and read the 2nd guage pressure
it will show how how tight your engine is 80 over 80 is perfect but never seen this method is used in checking aircraft piston engines faa acceptable is 65/80 mise showed 76-78/80 and no other leaks, but this method will show devoloping problems leaking valves,bad rings which cyl., blown head gaskets . thats my method , more time consuming but highly accurate in trouble shooting,

[tgreese]

You can buy a borescope (endoscope) for your phone for under $30. Take a look down the spark plug hole and see what's going on with the piston. The most common failure involves the rod bearing, but that's not enough slop to crush the spark plug. Usually you get a crushed plug like that when there is a foreign object in the combustion chamber. A piece of the piston? A piece of a valve? We could make a lot of guesses, but I think an inspection camera would help. If there's a chunk of something on top of the piston, that would keep the engine from turning over. Or take the head off.

You mentioned a camera, but no object in the cylinder. I would take the valve cover off and look at the tops of the valves. Maybe you dropped a valve into the cylinder.

[seventynine]

I have a endoscope. I checked all the cylinders. That # 5 cylinder piston top was all pocked up. I didn’t see any debris but it was hard to get a full view of it as I couldn’t seem to get the piston all of the way down. I’ll post a pic. Waiting on my friend to send me one (they are on his phone). I pulled the valve cover and in the amount that could turn the engine the valve closest to the firewall was moving . I’m not sure off hand which valve that is. This is on the 3rd cylinder back from the front on the drivers side. The other did not move but I may have not been able to turn it enough to get that moving.

[seventynine]

This isn’t much help but here is a pic inside the valve cover.

[tgreese]

If the top of the piston is damaged, something is or was in there. Diagnosis time has passed; I'd pull the head now. The pros would leave the carb on the intake manifold and pull the assembly. Same for the exhaust manifold - leave it on the head and disconnect at the pipe. You can readily do it yourself with a ladder, 2x4, and a strap or chain to make a hoist. BTDT, with much heavier manifolds and heads. Keep the pushrods, bridges and rockers in order so they can go back where they were.

[seventynine]

Right. Ok so assuming there is something in the cylinder…maybe part of a valve. I pull the head and see what’s going on.

If I fix the head…would the damage to the top of the piston require I replace it? Obviously barring it being cracked or the walls scored etc.?

I have lifts and hoists to easily pull it.

I know there are a lot of “if’s” in this question. I’m just trying to decide if I just pull the motor and swap another one in and cut my losses or dig a little deeper first. If I Iikely have to rebuild the bottom end either way there is no point going further while it’s in the Jeep.

[tgreese]

I would take a look regardless. It's my curious nature. Pulling the head is not that hard.

Yes, if the top is dented, I'd say the piston is toast. I'd want to have a look though. The pistons are fitted to the bores... patch up jobs, like a single new or used piston, are possible, but risky. You must rely on your judgement, and that may not be wise for an amateur. I don't want to steer you wrong - it's been a long time since I have done any engine rebuilding.

[seventynine]

Thanks Tim.

[seventynine]

Here are a few images of the piston. I included one from another cylinder that was not damaged.

There appears to something on the right side of one of them but it’s blurry. Could be part of a valve? Could be part of the plug hole though.

[letank]

Bummer, yes something hammered that piston... I am not an expert, only did camshaft swap a few years ago, and the usual hydraulic lifters before and a crank many decades ago... if it was my job, I'd pull the head(s) to see and then the whole engine to check the crank and rods. Engine stands can be tricky, I had a hell of a time to keep that engine where I wanted it.

Then you have to deal with putting the engine back on the AT and making sure that you did not loose the alignment marks, use a scrib not a marker! You seem to have all the right tools, so my comments are probably not needed.

Engine looks clean.

[tgreese]

Not much to add. Cool Cherokee - I like the color.

[seventynine]

Factory “Autumn Red” paint which shines up nice. It hasn’t been washed in 12 years in these pics. It’s completely original top to bottom and everything works as it did off the line…well except the motor now . Interior is near perfect minus a seam rip in the drivers seat. It has a little crust underneath but it’s real solid. 40k original miles.

I’ll keep you all posted on where this goes.

Thanks for the input.

[devildog80]

Only 40k miles on that engine, well worth pulling heads with anticipation replacing the one cylinder and running it.....providing that is the only major issue. With those miles the engine is just broke in, now ready to run another 100k+, and think you would be better off to get this one right, than get a different one you need to start from scratch.