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350 Cummins Seized

Discussion in 'Trucks' started by TheDud, Jun 12, 2018.

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  1. TheDud

    TheDud Member

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    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.
     
  2. Wes J

    Wes J Senior Member

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    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.
     
  3. TheDud

    TheDud Member

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    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.
     
  4. DMiller

    DMiller Senior Member

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    If it has water corrosion seized you will be doing a full in frame or regretting every failure after getting it loosened up.
     
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  5. kshansen

    kshansen Senior Member

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    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:D. 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!
     
  6. TheDud

    TheDud Member

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    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.
     
  7. kshansen

    kshansen Senior Member

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    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.
     
  8. TheDud

    TheDud Member

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    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.
     

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  9. TheDud

    TheDud Member

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    Thought I already uploaded this one.
     

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  10. DMiller

    DMiller Senior Member

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    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.
     
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  11. DMiller

    DMiller Senior Member

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    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.
     
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  12. TheDud

    TheDud Member

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    Awesome. Thanks for the info.
     
  13. kshansen

    kshansen Senior Member

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    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.
     
  14. DMiller

    DMiller Senior Member

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    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.
     
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  15. hvy 1ton

    hvy 1ton Senior Member

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    If it is a M939 series truck it will be a Cummins NHC-250. If it's something Canadian built, I got nothing.
     
  16. DMiller

    DMiller Senior Member

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    Turbo changes all possibles as the NH was Naturally aspirated, was noted a donor from a genset.
     
  17. kshansen

    kshansen Senior Member

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    Glad DMiller wrote all that saved me lots of typing!:D

    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!:mad:
     
  18. hvy 1ton

    hvy 1ton Senior Member

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    Reading comprehension is hard sometimes. I can't even really blame that, since there are pictures.
     
  19. RZucker

    RZucker Senior Member

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    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.
     
  20. TheDud

    TheDud Member

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    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.
     

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