New here. I recently bought a 6x6 truck with a 350 Cummins. The engine is seized, there was no air cleaner on it and the turbo was sticking up out of the hood so its been exposed to the elements. Sat for about 10 years. Obviously I want to free it up. I tried towing it in gear with a loader and it is seized solid. I dropped the oil, no water in it and it was pretty clean. I took the valve covers off and the oil filler must have let some moisture in, the rockers have some surface rust. Im thinking about pulling the heads, but i was wondering if anyone had some advice? Maybe i could take the injectors out and get some penetrating oil in there and a boroscope? Im thinking I might just be better to pull the heads and clean the cylinders up since it has been sitting.
That rig has unit injectors, so it won't be easy to pull them. We used to pour some diesel fuel or light oil in the intake and exhaust. Then hang a heavy weight from a long bar bolted to the front pulley. Let the oil work and eventually the weight will fall. But, don't be surprised if you don't have much when you do get it freed up. Rings will likely be sized in the grooves and will have huge blow by. The valves will also likely be stuck or no seal properly. I guess what I am saying is even if you get it turning, you're probably headed for a rebuild if you really want to have something that works right.
I wondered that. So I guess pulling the heads isn’t a bad plan. I have to change the oil pan due to clearance issues with the front diff so I may as well knock the pistons out while I’m at it.
If it has water corrosion seized you will be doing a full in frame or regretting every failure after getting it loosened up.
Like DMiller says if it's locked that tight you are looking at major problems even if you do manage to get it to turn. Now if it was just sitting a few months then you might, and that is a big MIGHT, get lucky but 10 years? Even if the pistons freed up by some miracle are the valves going to move before the piston smacks them? I see you are in Ontario, believe it might have got below freezing at some point in the last 10 years up there . So if water got down inot even one cylinder and froze that could have cracked the liner, no water in oil says maybe not but........I'm not that big of a gambler even with your money!! You might get lucky and only have one or two cylinders with rust in them but I think the minimum thing to do would be remove all heads as a start. Let us know what you find and post some picture, we like pictures!
Alright so definitely pulling the heads now. Have to wait a couple weeks before I can get back at it. I’ve worked on a lot of seized gassers and only had one that froze and cracked the block. But it does happen. Would have been nice if the intake was covered. As far as diesels go, we have a pettibone with a Detroit in it. That thing sat for 12 years and started with just a new battery and fresh fuel. I was hoping this truck would be the same way. Guess my luck ran out. According to the last owner, this Cummins diesel sat after a fresh rebuild, so maybe the lack of soot and grime buildup did it in. I can see the block was welded, it threw a rod out of the side. It was in a gen set so that’s why the turbo it top mounted. It was owned by a large sand and gravel business in northern Ontario so they weren’t afraid of spending money on equipment. Can I just pull the head bolts to take entire head off together? Doesn’t look like there’s anything stopping me. To reassemble it looks like I can back off the adjustment on the rockers to pushrods so nothing interferes when torquing. I will definitely post pics once I pull them. Thanks guys.
Okay before I make any more replies would need to know more about the engine. When I see someone mention a 350 Cummins the engine I picture is a 350 horse NT855(855 cubic inch) six cylinder engine with three heads either a "small cam" or maybe a "big cam". If you are not sure of exactly what that is a couple side view pictures, right and left side, of the engine will tell much more than needed at this point.
I thought I took more pictures of it on the sides. I have an ID plate here. I’ll make sure and take more soon.
Thought I already uploaded this one.
OK, is a NTC, but without an aftercooler not sure is a 350, in a M series US Military chassis. Can almost read the engine ID plate, not quite.
The rocker boxes have to come off first, the intake and exhaust as well. There are three heads, 18 headbolts per head torqued(hopefully) to around 320 ft lbs. There will be a small set of jumper tubes head to head and the main fuel lines either entering the back or the very front head at the end of the head. In that chassis could be a challenge to get to. Some head bolts will be inaccessible with the rocker boxes on and the pushrods in the way. With as much internal rust as I can see, the cam in that engine will need some serious looking over.
Awesome. Thanks for the info.
Amassing how much better info you can get with a picture! Like the old saying "One picture is worth 1,000 words". The only thing that might get more info would be the S/N or in the case of a Cummins the CPL number. Unfortunately I don't have access to that kind of stuff now that I'm retired but if need I'm sure someone can get it for you. Not sure what your long term plans are for this engine so that info would be helpful to those giving advice. Makes a big difference if you are just looking for something to run a handful of hours a year playing in the mud out in the back forty or will be using it several hundred hours a year doing heavy work trying to make a living. One little tip I would offer. If you are getting to the point of removing camshaft you will need to pull the cam followers of the right side of the block, three of them with six bolts in each. At least if it is a small cam, hate to say it but never worked on a Big Cam! And when you pull them off make note of which goes where and save as much of the gaskets for each as you can. Those gaskets are shims to adjust the timing of the engine.Knowing what was in there can save time latter on.
Big cam same same six bolts just wider pattern! Worked all the Cummins series H NH NTC, the little Monsters J, L, V engines and 90nuthins. The NTC series best longevity, BC1 and 2 series were good engines but still had cam flaking issues, major changes in follower roller designs, rocker shaft designs for the rollers even cup changes for push rods were not much better overall. N14 is when I stepped out of the market. To get the BC followers out the air compressor/accessory drive should be off, there is a timing fixture(I no longer have access to) and specs on cam gear offset keys as well timing point after TDC. You get that far in have someone do it for you. Upper counterbores are ALWAYS problematic, crack, distort, most are shimmed to get proper protrusion of liners for head seating and sealing. J and L series I never liked, the older Twin Disc injection pumps in iron hood flop fender monsters were enough to give a elephant a hernia. Push rods will oil fill as age, dropping them SLIGHTLY and LIGHTLY to a solid surface they will either bell ring or thud, thud is BAD and no way to fix but replace. Oil filled will distort on engine RPM rise and engine will miss, floating miss. Head bolts, ANY shank cracks or 'indications' above the thread line or below the head, DISPOSE. more than half bad buy a full set. Use CRISCO shortening on the lower liner seal, biodegradable and will not cause swelling, set the liner in easy then twist slightly then 'Set' the sleeve within the seals, best method I can quote. Lots of other upgraded issues as upper counterbores, interference fit upper bore sleeves, many many many improvements on these engines.
If it is a M939 series truck it will be a Cummins NHC-250. If it's something Canadian built, I got nothing.
Turbo changes all possibles as the NH was Naturally aspirated, was noted a donor from a genset.
Glad DMiller wrote all that saved me lots of typing! Only had one L engine and oher than a tune up never touched it, Most of the Cummins we had were in front end loaders, gen sets or haul trucks. NT335 was about the first up to the NTS420 in one haul truck, first V was one of the predecessors of V-1710 did do a few 1710's, then on to the KT1150 which got renamed the K19 when Cummins decided to talk metric. Agree on having someone run the cam timing if not going to be doing it a few times a year at the least. The most fun with that was the K1150/19 and V1710, no shims just had to pull cam and press off gear and figure out which new offset key to use and hope you did not put it in backwards and hope you did your math right. Oh and the 1710's had two cams to make it even more fun! Only had the pleasure of working on one V903. Had to argue with Cummins on their reman heads that did not meet spec's causing a miss when cold due to valves recessed into the head way beyond spec's in book!
Reading comprehension is hard sometimes. I can't even really blame that, since there are pictures.
I think that engine is going to be a huge money pit. In '98 you could buy the proper Cummins NH 250 military surplus Fan to flywheel engine for $3200 ready to install. Had all the accessories installed an came in a sealed container. I'm betting there are still some floating around, price might be higher.
Ya I was told it was a 350 big cam Cummins out of a gen set. And then the old fella told me a story about the piston rod going through the side of the block and replacing it with a 400 cummins, then putting this 350 into the truck. I was also told that it would ‘probably’ still run. So I’m going to fact check before I go with any assumption haha. Looks like the block that’s in it has has a piece welded in so it’s the one that blew up. So I’ll take some pics of the sides so I can tell if it’s a big cam or not. Here’s some pics of the truck. It’s an M813a. It originally had a 250 in it, I just had it delivered last weekend.
Trying to break free
Truck model
If it is seized to the point of a rebuild you may be as well off to reinstall a old NH250. Damn things would run seemingly forever and financially could be the better alternative.
Yes, if you don't "need" the 350 horses and can find a good running 250 that would be a good idea. Nothing against "MORE POWER!" but horses cost more money. A nice running non-turbo NH 250 with minimal care could out live most of us old timers on this forum!
Once I pull the heads and see what I’m dealing with I may look for a good used engine. The spare 250 I have isn’t complete so it’s a dead end.
I too think good money chasing bad. It would be cheaper to buy a used or rebuilt engine from a dismantler than to open this can of worms.
Just doing a quick Google search came up with this place that specializes in military truck and appears to have several NH250's in various conditions $4,650 for a complete running take out. Sure would be something to at least think about before putting a pile of money in to the 350! Just looking online for rebuild kits for the 350 the best prices are in the 900 to 1,000 range and I have no idea of the quality of the parts in them. then if your turbo has a problem did not check price on that. Then add in maybe some basic head work and injectors, as if the water even touched them that would be a no go to reuse them. As much as I like fixing things unless you have something you are trying to keep 100% original, which is not the case here, some times you will be better off just tossing the bad engine and slip in a good used engine. Instead of spending weeks of your spare time rebuilding an questionable core engine you and a couple buddies could take a long weekend and have a running machine. Might even have some time to go play in the dirt that weekend!
Welded block, uncertain the internals, uncertain if EVER was or will be functional, buy the runner and swap!!
One thing to consider too, these 5 tons had enough transfer case troubles with the 250 and overloads. Originally that series truck was designed with a Continental 6602 gas burner. Worked on a few being used to pull semi trailers loading potatoes, the farmers went back to using a 4 wheel dolly pulled with a big tractor.
RZucker has it nailed. The driveline in those 5 tons will never handle a 350 or 400 cummins. But I don't think what you have is a 350 with no aftercooler. If this was never a completed truck, you may have other problems - a gen set motor will typically have a different governor set up than a truck engine. The newer 5 tons- some have 250 natural aspirated big cams. Some have 8.3 cummins. Either ones are good engines. I don't know what you gave for the truck, but used military 5 tons in running and driving condition don't bring much on the military surplus sales. I bought two a couple years ago, they were both under 30,000 miles, drove on my trailer for under $4,000 each. not a thing wrong with either one. Sell/ part yours out for a rock crawler (for the axles) and find a runner. You'll have way too much into this one.
Would be interesting to know the design criteria for some military equipment like those trucks. I doubt they are designed and built to be running hauling loads a couple hundred thousand miles a year like say a Peterbilt or KW! Probably more effort is placed on profit for the contractor building them than anything else.
Yes, if experience with generators is any indication, they build them to a set of specs drawn up by a bureaucrat with no consideration for how it actually works, if at all. Then somebody gets the contract at an extreme low bid, builds a bunch of them, and goes out of business. Then maybe a different builder picks it up, builds some more, and goes out of business.
As well documented, they are designed to be 'Expendable' and short lived but durable enough to get a job done.
The average mileage I saw on M-123 10 ton trucks was around 2500 miles when they were surplussed.
Don't anyone get me wrong on the comment I made regarding design life of some of the military equipment. I fully understand that it is a sad fact that many of them have to be considered disposable so to speak. Back before my dad was shipped overseas during WWII he was working as motorcycle escort duty in the Southern states. I forget the miles he mentioned but there was a set mileage that they would use the Harleys then a new engine would be installed. Faster and easier to keep a bike ready to go that way than to have trained mechanics fixing problems that might come up. The time needed to replace an engine was way less than doing even a simple bit of trouble shooting and repair.
It seems to me that military equipment get built from a boiler plate spec so that they are all exactly the same. Problems and all. They don't get the running product improvements like civilian trucks and the like, when the manufacturer sees that something is junk they fix it so there are not warranty and angry customer issues. I wonder what kind of warranty the military gets?
Military equipment is pretty well sold As Is under Customer Contractual Design Criteria. It fails due to a catastrophic component failure they will replace the major part but the small crap is on US.
What's aggravating is that the military does things their own way for no explicable reason. I was looking at specs for some road tractors. Just plain Jane trucks for pulling trailers on paved roads. I think they were A M General, but I can't remember. Looked like regular trucks from the outside. Cummins engine and Allison automatic, nothing wrong there. All 24V electronics. All governed at about 50 mph. Probably livable. But, the stupid 5th wheel plate is about 8" taller than any other truck in the world. They can't tow a non military spec trailer and a military spec trailer can't be towed by a regular truck. Only the government could come up with that. I see military trailers being hauled all over the country on the back of a flatbed trailer. Nobody can just hook up to them and go. I'm sure there is no surplus market for trailers no one can tow. What a waste.
The fifth wheel height is to match up with the 6x6 tractors they use in off road situations, otherwise they cant get all the product out of fuel tankers. Also some of the real heavy tank mover trailers used a 3" kingpin.
With a cummins and allison it'd have to be a M931/M932. They aren't governed at 55 that's all it's got with 11R20's. The A1's with 14R20's will top out in the mid 60's. I know a farmer that has two 931's that pull hopper bottoms out of the field. It's doable, but they don't ride level.