Stuck Valve, Ford Lehman 120 - a bit dire.

[Wotname]

That is sort of good news! You are halfway to getting it fixed

[wilsod3]

Originally Posted by Boatguy30

Is the push rod bent? I've used a large drift to "loosen" and replaced the bent push rods on those motors before..

Yes - the push rod is very bent.

[Cheechako]

Originally Posted by wilsod3

Good point. Just removed the rocker. Push rod totally bent!

Easy fix and you are lucky! Great to hear. I had a push rod simply come off one rocker on my Perkins 4-236. The rod was NOT bent! I have no idea how that happens, but CAUTION:
it's highly possible your push rod bent because you got water in one cylinder! So check that out!

[Compass790]

Pleased you didnt try dead heading your injection pump.
I bent a pushrod squirting too much oil in air -intake so check what post 33 said.
The bend was not bad so hammered it straight in vee blocks but wouldnt recommend that for big bend.

[CassidyNZ]

I’m sure by now you have checked the valve associated with the bent pushrod? That it’s at the same height as the rest?

If it were me, I would not be happy until I’ve identified the cause of the bent pushrod. I’m not sure if Lehman engines are forgiving when valves stick down but I’d be surprised if they were. You may have got real lucky when valve meets piston but it may not happen that way twice.

Do some research, find out why.

[sealife2]

hi there
I've run a couple of those engines in commercial service they are great and inexpensive parts mostly
i would for sure take the head off to determine the cause of the problem if carbon sticking the valves all valves guides and seats should be checked over reground replaced as required .
if its water intrusion again the valves should all be checked as well as the con rod in the cylinder with the bent push rod those engines get bent con rods fairly easily with a small amount of water. im going to assume you will look for the cause if its a water problem
be very very careful when working with the water cooled exhaust manifold they are very expensive and they corrode around the bolts/studs holding on the end caps and strip on reassembly there is not much meat to helcoil into if you do strip one of the studs or bolt. and a good used engine can be less expensive than those manifolds .
best of luck
jake

[topmast]

Some engine rocker assembly get their lube from an external connecting pipe from the main oil supply. Others ( like the smaller ford,) use an internal under the rocker cover connection. using a little Oring to prevent oil from just dribbling back into the gallery instead of running the full length,, so little lube reaches the valve stems .The valve stem doesn't like this ,the push rod feels its pain and ,,,sprung...

[CaptJPMcGuire]

You might determine which cylinder is doing the misfiring or not fully function --therefor has a bad valve. Try running engine --loosen each injector a little bit --one at a time and take note of engine rpm and sound. The bad cylinder will not have as much affect as the good ones when taken off line.
I think--but I'm a hack mechanic and this is a cheap way to check

[lituya1617]

WILSOD3: I have been a professional mechanic (licensed aircraft, marine, diesel) and a boat owner since 1965. I had a vessel with a 120 Ford L. in it and I completely rebuilt it - new sleeves, bearings, gaskets, pistons, rings, etc. It ran for over 15,000 hours thereafter. Before you start, make sure the valve really is stuck. A stuck valve in this overbuilt engine is a rare problem. The valves usually stick because of carbon on the stem but that indicates that the injector is putting out too much fuel or the compression is bad in that cylinder. After you verify that the valve cannot easily be freed up with some penetrating oil and a bit of jumping up and down, you had best pull the head. It is not hard nor a prolonged project. It is really no problem to get the head off the engine (but be careful not to damage the injectors unless you remove them first). I leave the injectors in place if I can. You will need the overhaul manual to make sure you do it right. The head weighs about 200 pounds so plan accordingly. Two guys can lift it easily and carefully. Unless your diesel has 10,000 hours or more on it, you probably will not have to do anything to parts other than the head. These diesels are darn near bullet proof and will run forever if you keep them cooled and put oil in them when the time comes. While you have the head off you can either fix the valve problem yourself or have it done by a pro that does heads. Turn the head upside down and leak check the valves before doing anything else. It may be that all the valves seal fine except for the one that is stuck. If so, you will only need to fix one valve. No need for a professional mechanic for that job. Take off the rockers, remove the keeper and spring (do not lose the keeper - it will fly if you are not careful) and push the valve out. If it is bent or badly burned (assume it is the exhaust valve usually) you have to replace it. If it is stuck because of carbon (you will have to check the corresponding injector) but is otherwise unharmed, clean it, lap it in, replace the valve guide and seal, grease it well and put it back in. If you can determine why this one valve stuck, do it. It usually means a bad injector or low compression so check the rings for leak down with some diesel, check the liner for scores, and check the other valve in the same cylinder for proper seal. If it is only a warped valve, replace it and lap it in. You can do this yourself and save a bundle. Be careful to reassemble according to specs and do three stage torque on the head bolts. If you have to do one injector, get them all done and balanced even though it is expensive. You should make sure fuel filters are OK because injectors usually fail because dirt or water got to them. Just follow the overhaul manual. There is nothing tricky about this engine. Good luck.

[like-a-child]

Last year I had my '76 Lehman 80 rebuilt for around $7k parts and labor here in Tampa area. Included 2 new pistons, head re-condition, new rings and rods, rebuild 4 fuel injectors. Mechanic said it was likely first ever rebuild on it so they are great engines.

2 great parts sources here in US but I prefer Brian Smith at American Diesel 804-435-3107 where I also got new original owners guide and service manuals for about $35 each. Brian's dad helped design the Lehmans and ran the factory for years. He knows everything about them.