M939 engine swap to NTC-300?

[jdknech]

so I hear (read) on here all the time, that the best upgrade for power is a engine swap.. so I have been looking for a good option to swap into my M932A1 (kinda hard when you dont know much about "large" diesels) but i stumbled across this NTC300, I have not seen the engine, but as near as I can tell its a big cam? from what i have found online the NTC300 only came in a big cam.. is this true?

also, has anyone actually made the swap? i have searched, and come up with lots of talk, but didnt find anyone who has actually done it.. Is is a direct bolt in as far as the engine? i know i will have to move the coolent tank, and some other odds and ends, but just kinda want to know what I'm getting into before i buy this MASSAVE engine..

Fire away guys...

 

[m16ty]

I'm not familiar with the NTC-300 but any 855 Cummins swap is pretty straight forward. You may have to swap the front cover on the 300 with the one off your 250 and maybe stuff like your fan and such but it's pretty much a bolt on conversion. Only other thing is you're going to have to make room for the turbo.

I've never done a swap in a M939 truck but I've swapped a bunch of Cummins engines in civilian trucks. It's just been awhile and I don't remember the specifics.

 

[diesel dave]

You may be able to increase the power of the 250 (turbo ect) cheaper than a swap.however,I personally inquired about doing this with an 814 that I own. The company I asked had done this to 2 of their own trucks. Easily done and fairly inexpensive,but it seems the rest of the drivetrain didn't like the increase in power. They didn't recommend doing it. Has anyone else have any real experience with increase power?

 

[rangereter]

You will also have to switch flywheel housings due to the passenger side engine offset and SAE#2 allison trans housing (engine/ trans bolt pattern diameters) ...I wouldn't think going from 240 to 300 HP would be too harsh on the drivetrain if operated sensibly. If the 300 is kind of old and tired or out of tune or both, you might not notice much power increase anyway (hope that that does not end up being the case if you end up going this route).
Regards, Bob

 

[jdknech]

You will also have to switch flywheel housings due to the passenger side engine offset and SAE#1 allison trans housing (engine/ trans bolt pattern diameters) ...I wouldn't think going from 240 to 300 HP would be too harsh on the drivetrain if operated sensibly. If the 300 is kind of old and tired or out of tune or both, you might not notice much power increase anyway (hope that that does not end up being the case if you end up going this route).
Regards, Bob

thanks for the info! so could i just use the bellhousing from the 250 thats in there now? and i will be rebuilding the engine before install, so it shouldnt be "tired" i might even crank it up to a 350-375HP while im there..

 

[poorman4x4]

I'm planning a Cummins 400 swap, all 855ci cummins are the same big cams are slightly taller, your factory allison 654 bellhousing will bolt on the new motor, motor mounts are the same, have to move the surge tank, because of turbo. Reconfigure the intake pipe to cross over motor to turbo intake, then make new pipe to hose back across from turbo to intake manifold where original pipe came in from air cleaner.

 

[poorman4x4]

Its hard to do a swap when your 250 still runs, hard decision to switch out a perfectly good engine

 

[jdknech]

I'm planning a Cummins 400 swap, all 855ci cummins are the same big cams are slightly taller, your factory allison 654 bellhousing will bolt on the new motor, motor mounts are the same, have to move the surge tank, because of turbo. Reconfigure the intake pipe to cross over motor to turbo intake, then make new pipe to hose back across from turbo to intake manifold where original pipe came in from air cleaner.

sounds like you have done your homework! this is what i was neededing to know... i will be doing the swap at work, but only have one night to do the major part of the swap (meaning the lifting and bolting the new one in) i work for a airline, and i was told i could use the engine change bay (has a overhead crane) but only for a night.. so i need to know what i am getting into before i jump into it... also, does the front cover from the 250 small cam fit a big cam?

Its hard to do a swap when your 250 still runs, hard decision to switch out a perfectly good engine

well when i feel like my deuce was a sprint car in compairson, it kinda helped me pull the trigger on the swap.. plus my brother can use the 250 in a dump truck that has a rod through the block..

 

[poorman4x4]

It should, do you need it? Is the cummins 300 damaged? The pulleys stay the same, besides the a/c compressor mount, most are mounted where your 250 power steering pump should go. Compressor and fuel pump are inline gear driven and your generator should mount where the alternator was at on the 300, make sure you use all the 250 brackets to switch over to the 300, cummins 250 lack piston coolers the reasoning behind the non-turbo setup, but i mean hey guys add turbos off cummins 290's and a pyrometer and dont have problems, to each is own but a engine swap is not incredibly hard.

 

[poorman4x4]

By the way is the 300 complete? what big cam gen is it? you can tell by year or data plate in front of the compressor where it meets the block. usually googling the serial number will tell you the gen.

 

[jdknech]

It should, do you need it? Is the cummins 300 damaged? The pulleys stay the same, besides the a/c compressor mount, most are mounted where your 250 power steering pump should go. Compressor and fuel pump are inline gear driven and your generator should mount where the alternator was at on the 300, make sure you use all the 250 brackets to switch over to the 300, cummins 250 lack piston coolers the reasoning behind the non-turbo setup, but i mean hey guys add turbos off cummins 290's and a pyrometer and dont have problems, to each is own but a engine swap is not incredibly hard.

i was under the understanding the the front engine mount was attaced to the front cover on the 250, and it was not that way on the 300? i have not got the 300 home yet, so i have not really got to go over it well yet.. but i know my luck, and if i just turboed the 250, it would have a meltdown in about a week or less.. in other words- I push my luck (with my toys)

 

[jdknech]

By the way is the 300 complete? what big cam gen is it? you can tell by year or data plate in front of the compressor where it meets the block. usually googling the serial number will tell you the gen.

i do not have that info yet, but should have it in about a week... i got the engine for the price of a used turbo!! and it is all there from the fan-to-bellhousing

 

[poorman4x4]

i was under the understanding the the front engine mount was attaced to the front cover on the 250, and it was not that way on the 300? i have not got the 300 home yet, so i have not really got to go over it well yet.. but i know my luck, and if i just turboed the 250, it would have a meltdown in about a week or less.. in other words- I push my luck (with my toys)

got ya., a cummins 290 and 300 and 400 do all look alike, im pretty sure (about 90%) that the front engine mounts will fit all of them, considering you can build a 290 to 400 specs there hard to tell apart, the only thing i noticed different was either the single or dual oil filter setup on the passenger side of the engine

 

[jdknech]

got ya., a cummins 290 and 300 and 400 do all look alike, im pretty sure (about 90%) that the front engine mounts will fit all of them,

ok, cool! that was the info i was needing.. so has anyone actually done this swap yet?

 

[topo]

You might check the height of the fan some engines had the fan lower or higher then others .I would take a good look at the oil pan on both engines . Cummins engines have had a lot of diffrent oil pans through the years made all over the world . Good luck with your build .

 

[bearboley]

Telling if the 300 is a big cam is easy it will have big cam cast in the left side of the block. Then its just as easy to tell what generation its because it will say big cam,2 3 or 4 in 2 inch letters. You have to look up the cpl # to see how the motor was internaly set up as to how much hp it will make. Big cam only means the cam is bigger in dia. Allowing for greater flexability in injector and valve timing by means of shims under the cam follower. The extra height come in to play because of the ntc's intercooler and intake, if it has a jake on it the valve covers will be higher also. I would just put the turbo and the pump off the 300 on your 250. It would make the same power with a lot less work.

 

[jdknech]

so is there a reason I would want the big cam over the small cam? whats the "max" horsepower a small cam can put out safely? (talking about a civy engine with piston coolers) there are a few small cam engines close to me for rather cheap as well.. one of them is a 315hp

 

[Stevepala]

I'm in the process of putting a big cam 400 in my 929 currently. My motor is a recent rebuild and I had it running on the ground over the weekend. Like other people stated the motors are nearly identical with a few major differences. Having a jake makes the valve covers 2.5" taller which might interfere with cab clearance at the number 6 piston. You may need to cut and weld clearance into the cab. Also being a big cam the front covers are totally different and will not interchange. The big cam cover has a built in cam support, small cam does not. The motor mounts are not interchangeable, small cam is a trunion style, big cam bolts to front cover. The harmonic balancer on a big cam is larger in diameter, needing more clearance. To make the motor sit correctly on the front mount I'm seeing a torch and welder is required to mod the front cross member, not that hard but time consuming. I'm not transferring anything from my small cam motor to the big cam. The water pump, power steering pump, are all staying on because they are also totally different. A few bolt holes on the bell housing needed to be modded also.

Depending on the series big cam 1,2,3 or 4 will make a difference. The series 4 have a low flow coolant system, stay away from them or convert it back to the older style coolant system.

Big cams also have piston oil squirters to keep them cool from the added heat of a turbo and bigger injectors. If you put a turbo and pump from a 400 onto a 250 I don't think the piston will last very long as heat and pressure increase.

I would be very interested in seeing what type of front motor mount is used on a military truck that are factory fitted with a big cam.

This is not a one night swap, the front motor mount is the issue.

By the way I don't know everything just telling you what I have ran into so far.

Steve

 

[Bolkbich]

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[73m819]

Something to think about with these engine swaps

The 855 had TWO types of front motor moumts, each has a DIFFERENT accessary drive cover (the covers are interchangeable as far as mounting to the front of the motor), one is the TRUNION mount (there ARE two types of these, military and civi), the other is the under the front of pan mount., the trunion mount has the snout that sticks out from the cover, this sits down in a "U" shaped mount with inserts, the civi "U" and inserts ARE different then the military and WILL NOT WORK in the military truck, at least for the 809/900 5ts, not sure what is used on the 915/920s.

I found this info. when I was sourcing parts to repair the damage from the landing (could not read the landing section fast enough in the "FLYING THE m819 TM", did read the takeoff section) when I came up with the idea that the m819 WOULD make a GREAT flying crane.