NHC 250 BLOCK with PISTON COOLERS??

[hardtime]

Greetings,
I am interested in the turbo conversion for my m814. I came across a cummins info site and it was described that the late 250 blocks had piston coolers. My wife called Cummins with the block #'s and they said it was an 1981 block. Can anybody offer any info. If it is true I was thinking I would able to use a turbo that would make more than 8-10 psi boost. I live in the mountains and would like to produce as much power as possible with out melting pistons.
Thanks for any help.

 

[jatonka]

I am happy to see you are doing some checking before just bolting a turbo on to one of these NHC 250s that are actually a 240. The original nat. Aspirated 250 was not built for a turbo. The piston oilers were not there. Very short life expectancy if you add a turbo.

As you investigate the later blocks, you would help us very much if you would share your gained knowledge with us on the 250s that will function well with a turbo. Thanks much for your common sense, John T

 

[M813A1]

I would also like to add the oil cooled pistons to my truck , so I could do a little tweaking to get a little extra power out of my NHC 250 without burning it up !!

 

[m16ty]

I would also like to add the oil cooled pistons to my truck , so I could do a little tweaking to get a little extra power out of my NHC 250 without burning it up !!

It's not as simple as changing the pistons. The piston oil coolers come out of the block and squirt oil onto the bottom of the piston to help keep it cool.

I've got an old Super 250 in the barn. It's basically a NHC 250 with a turbo added. I haven't looked at it to see if it has the piston oilers but I will and report back.

There are also hood clearance issues to deal with when installing a turbo in a 5-ton.

 

[WillWagner]

Super 250 is very different than the NHC. It would be easier to go to the bone yard and find a good running NTC and swap the two. The original Super 250 was the old NH engine with a "smoke kit" installed. It was a 5 1/8 bore engine.

 

[area52]

Looks like jwaller did it:

http://www.steelsoldiers.com/5-ton-up/28133-818-now-turbo-pics.html

 

[Sephirothq]

How can you tell by looking at the outside of the block if piston coolers are present? I am also looking to add a turbo to my 250. I have access to one from a NTC 400. I was also wondering if i could add the jake brakes, and what that would require?

 

[jwaller]

How can you tell by looking at the outside of the block if piston coolers are present? I am also looking to add a turbo to my 250. I have access to one from a NTC 400. I was also wondering if i could add the jake brakes, and what that would require?

yes you can add all that stuff but you will need to mod the hood bc it's too tall to fit. if you look at your front valve cover now it's almost touching the hood as is.

 

[martinsaunders06]

How can you tell by looking at the outside of the block if piston coolers are present? I am also looking to add a turbo to my 250. I have access to one from a NTC 400. I was also wondering if i could add the jake brakes, and what that would require?

When i fitted a turbo on mine a year ago i spoke to cummins uk and they also said the later block 250,s had piston cooler nozzles but my block is 1984 and as far as i can see mine doesnt?but that is based on the fact that if it does then the block should be cast with 6 raised horseshoe shaped casts adjacent to each cyl liner with threaded inserts(the cooler nozzles) which run along the lower block and are below the exh manifold ?. whether they do or dont my 250 with turbo has been lugging my 816 wrecker/38500lbs sometimes with the m35 on suspened tow and touch wood has been faultless. the engine has less diesel knock, runs cooler under load and sounds wonderful. (my block has the castings but no threaded inserts drilled into them),martin

 

[martinsaunders06]

yes you can add all that stuff but you will need to mod the hood bc it's too tall to fit. if you look at your front valve cover now it's almost touching the hood as is.

There are many ways of piping it up but for me i found running the intake to the rear bulkhead meant the hood was fine without altering it . that was with 3 1/2 inch piping and worked great
JWALLER yours has probably done the most miles since fitment and be interesting to know how yours is going please?

 

[powersmoke18]

actually cumins did turbo engines without piston coolers. you just have to get the fuel and air just right. egt gauges are your best bet for not melting down your engine. keep it around 1150 degrees and it should be fine. im currently in the proccess of adding one to my truck. but i'm gonna change out the injectors to soo who knows whats gonna happen.

 

[jwaller]

There are many ways of piping it up but for me i found running the intake to the rear bulkhead meant the hood was fine without altering it . that was with 3 1/2 inch piping and worked great
JWALLER yours has probably done the most miles since fitment and be interesting to know how yours is going please?

it's going very well. I prob have about 7k miles on it now since conversion.

sorry I missed your post when you originally made it.

I am thinking about putting jakes on the middle and rear cylinders so I might be redoing my pipes soon. If and when I do I'll post some pics of it all.

As was said in the previous post. You must get the afr close when running the turbo on our motors. you don't want to run high EGT's without piston coolers. But if you leave the fuel alone and just install the turbo, you will lower your egt's and you should be ok.

 

[powersmoke18]

totally understand jwaller well the turbo part no. that you want to use is AR12600. thats good all the way up to the 290. they used to use that turbo to increase the power of a 250 cummins with no piston coolers to around 270. thats the cummins recommended hp increase. so i'm gonna put 270 injectors in it. cause simply increasing the fuel pressure is not a great idea on these motors. doing so is a great way to bend pushrods.

 

[Sephirothq]

Can I use the turbo from a 400 or will it produce too much boost? I still didn't get a chance to get the parts from the engine. I am thinking it might be an m915 engine. I was going to get the jakes and the turbo setup for my 250. I understand the hood clearence issue, I am also concerned if there will be a turbo compatibility issue.

 

[powersmoke18]

any cummins big cam turbo will work. but there are a few diffrent turbos for the big and small cams all of which are designed to work diffrently. to much air can reduce power.

 

[powersmoke18]

hey guys!! found this info incase anyone wants to up the hp a lil bit. egt gauge highly reccomended!!!!!!!!! the buttons with the N's prior to the numbers fit our fuel pumps!!