The Stovebolt Site Forums The Parking Lot Big Bolts cummins 350 help

this isn't GM but i thought this was the best place to put it. i bought a '72 peterbuilt cabover semi that has a cummins 350 in it and it had a bad knocking sound so i pulled the back head(1 of 3) and didn't see anything wrong and it looks like it was recently rebuilt so then i pulled the oil pan and found some broken pieces of what i think is a sleeve, i think they came from #3 cylinder because that piston is loose. so my question is do the cummins engines have a sleeve like a Detroit? if they do can the old one be pulled out and a new one be pressed in along with a new piston and rings on just that one cylinder or do i have to rebuild the whole thing? the truck probably wont get used allot but when it does it is usually pretty abusive.

Hy 47chevy6400, yes Cummins engines are sleeved, and can be rebuilt one cylinder at a time. Satisfy yourself that the same thing won't happen again, before sticking it back together, in other words, figure out what caused the damage in the first place.

Cummins uses a wet sleeve compared to Detroit's dry sleeve. The 72 was a pre FFC small cam engine. which means it did not have piston cooling. They were very prone to piston galling. That is when combustion temperatures got past the melting point of the piston and the piston actually sticks to the sleeve. The good news is that cummins parts are very cheap compared to Detroit and cylinder kits are sold individually..That is a cylinder, piston and rings. Whoever, the knocking you are hearing is probably a liner that is loose. When liners are installed, the liner protrusion at the top must be shimmed correctly and the counter bore must be correct which takes special tools, but it can usually be done with out pulling the engine. If you have never worked on a cummins, it is really not something you can do your self. Find an old mechanic who has experience with these old engines to help you. By 79 cummins had improved their engines greatly. They had FFC piston cooling, the big cam and improved turbos. And they were a lot easier to drive. Drivers had to constantly keep their eyes glued to the pyrometer to watch combustion temperatures to prevent this from happening. By the late 70's a pyrometer was no longer necessary and the engines had a much wider operating range. My first cummins was a 1964 model and I have used nothing but cummins and I have watched them evolve. You might want to replace the small cam with a big cam emgine. i am not sure what you mean by abusive use, but the old cummins could not stand abuse. I would be glad to discuss the matter over the phone with you to keep the posts from getting too long.

this one looks like the piston seized to the cylinder and pulled the whole thing down then the crank broke it in pieces. could it have anything to do with my dad driving it at 4000RPM. how do i know which engine it really is? I think the engine and trans might have been swapped a some point because lots of the gauges don't even have their sensors.

How in the world did he get it up to 4K????????? That one's supposed to be governed at about 2150! With the weight of the rods and pistons, I'm surprised there's anything left of the crankshaft! The fit of the sleeve in the block is critical, as any wobble allows coolant leakage into the crankcase, and promotes sleeve breakage about the middle, resulting in exactly the symptoms you're describing. If it's a fresh rebuild, the sleeve projection above the block might have been set wrong on assembly, or the lower ring in the block where the coolant seal ring fits might be oversized, letting the sleeve wobble in the block. The fix there is to bore out the lower sealing ring, and install a short piece of cylinder sleeve in it. That's an out-of-the-frame overhaul procedure, which can get VERY expensive!
Jerry

i don't think the governor works. I'll just say down hill, load, first time driving it. he said it didn't sound like the rpm was that high. i was riding with him watching the tach the whole time.

Not relevant to this discussion...
But Detroits use wet sleeves, the coolant contacts the top portions of them. The bottom portions of them are in the air box, and are dry. With the exception being a few of the aluminum models used completely dry sleeves, but these are rare.

Grigg

I have worked on Detroits because I had to. We have had several in yard mules, fork lifts and compressors and still have one left. We call them dry because they do not have the require a seal at the bottom like a Cummins and they don't get pinholes in liners like cummins did in those days. I really doubt that the engine was run up to 4000 and I doubt that the tach even shows over 3000. We used to run our non FFC 350's up to 2600 on upshifts on upgrades. I would rather think that the engine was lugged. It was very important to have a pyrometer on those engines. The piston gets hot enough to expand and it sort of welds itself to the liner. Galling a piston or pulling a liner was quite common. I have seen exactly what you describe many times on engines without piston cooling. If it were my engine, I would scrap it and buy a big camIII engine of about 83 to 86 vintage. They have the piston cooling, the long head bolts, and if they have been overhauled, they probably have been machined for lower press fit liners. They are the toughest mechanical injected cummins we ever used and they fit without modifications.

not trying to argue but the tach does go to 4000 and the needle was jumping between 3500 and 4000

well then, while we're not arguing, a two cycle Detroit Diesel does have a seal between the wet liner and the block. I have both a parts and service manual here in front of me.

I think it is just a difference in terminology, We called cummins wet liners because the entire liner was surrounded by the water jacket and the Detroit didn't. As far as the seal, yes there is a seal, but it is not a problem area as it was with the old cummins. However, I still question if the engine was running 4,000. Especially after the damage he describes sounds exactly what happened to the old engines when they were lugged. I have known engines to run away and self destruct from either a Detroit blower or a turbo passing too much oil, but this was in a no load situation, either between gears or in a shop. Except for 1 60 series which dropped a valve while still in warrranty, I have run nothing but cummins in my over the road trucks for the past 40 years. It's been over 30 years since we had one to pull a liner so I guess there's no need in worrying about it now any more.

so after the head and piston are out does the sleeve have to be pulled out with a special puller or could i just pull with a slide hammer or something. also could it be possible that if this isn't the original engine the tach doesn't read right? or are all of the tachometers the same? i was out working on getting the head off today and the block has a rebuild tag on it that says
STD. STD.
NTC 350

is there some kind of casting difference between the small and big cam 350?

We have a special puller because we used to do a lot of inframes. However, I have seen pullers improvised using a porta power or modifying a puller to work, However, if the piston pulled the liner, it will come out easily. However, once you have the liner out, you need to check the counterbore and the sealing surface where the seal and rubber o rings seal. It needs to be very clean and free of rust. If there are pitted spots in it, we used to fill them in with bondo and prepare the surface like one would to paint it. Here is a website that explains checking the counterbore, and the liner protrusion after you install the liner. Liner protrusion is adjusted by brass o ring shims. http://www.tpub.com/content/automotiveenginemechanics/TM-9-2815-226-34-1/TM-9-2815-226-34-10100.htm

so how about the difference between small and big cam and how to tell the difference?

Big cam will say big cam on the side of the block. They made a I,II,III,and IV. The I used short head bolts that cracked the deck of the block II and III were both good IV used a special radiator for the aftercooler. They started making the BCI in 77, the II in about 80 and the III in 83 and the IV in 87 and then of course came the N14 which was available for a few years in Mechanical or electronic injection and then electronic only from about 93. As for the tach question, I think mechanical tachs are pretty much standard. They drive off the fuel pump with a cable like a speedo. If a cable is really dry or the head is rusty it will show grossly false readings. I don't think your problem was from over speeding. These engines were meant to operate between 18 and 21. Allowing an engine to lug at 1600 would easily do the damage you describe.

The later good ones (mid 80's) have BIG CAM casting letters on the camshaft side of the block, which is the same side as the injection pump/air compressor. I also believe the cam follower boxes where larger on a Big Cam--maybe crenwelge can confirm this. The small cams were a little before my time--either wrenching or driving.

My favorite Cummins is a Big Cam III. They were a good dependable engine. I didn't like the cooling system on a Big Cam IV. Heat is the arch-enemy of these old Cummins engines--they don't tolerate temperatures much over 180 for very long

started out on a small cam 290 cummins. moved next to a big cam1 290 thought I'd come up in the world very dependable.

Hey racecarl, I see you call McCook home. I was a witness in Cornhusker's litigation against Hobbs in 71 and have used Cornhuskers all through the years. I have 9 of them at the moment. Its been quite often we loaded corn at McCook when we picked up new trailers. And it gets you around the scales at Hebron and Bellville. By the way, the cam followers are srikingly larger on a BC than a small cam.

Thanks, crenwelge, for the info. In the past a LOT of our local corn went to the Scott City, Kansas area for all the feedyards there. We now have ethanol plants in Trenton (25 miles west) and Cambridge (27 miles east) so not alot of corn leaves here unless it has already been ran though the ethanol plant. This has really been a good deal especially since fuel is so high-priced now.

The most popular trailer around here is the live bottom trailer used to haul distillers grain from the ethanol plants to farms and feedlots. These trailers have a double chain with large rubber flabs attached that 'poops' out the wet distillers grain wherever the customer would like it. Often times the driver will load up on grain corn at the same farm and haul it back to the ethanol plant.