818 now with turbo and pics.

[bubba_got_you]

I agree with Jwaller. The small oil line is a concern. Discharge oil tends to be whipped full of air, like top of a black cappuccino. The nat aspirated heads are the ones with the open ports though I'm not sure if that means all of them. They do get swapped sometimes. Pretty easy to tell if you have them. Plugging them adds 1 psi at WOT redline. Power increase from the change will be insignificant if you are under fueled because all you'll get is an added push on the piston during the intake stroke. Same can be said for adding a turbo. Adding fuel raises boost. Pretty quickly too.

I tried to update post #72 a while back but could not due to some new policy. Basically, another year w/no problems of any kind, always cool egts, ~700-750*F, 800*F max (post-t probe), enjoy the whistle off idle and being quiet at speed, maybe 280-290hp the way it is currently fueled, more than made up for what going to super singles lost.... Still a dog by big rig standards (about as kindly as can be said with the current SS rules of conduct policy). Compared to a my ex wheezing de-rated old EM7-315 Mack- the NHC-T uses twice the fuel and makes half the power. To be fair gearing is also a factor in that comparison.

yes i would up the size of the line. 1/2" is not even good enough for my 6.2 turbo, i found that out when i had a blow out through my exhaust

 

[Boss Doug]

opcorn:opcorn:opcorn:

 

[martinsaunders06]

PMS? i think it might be a good time to get used to people wanting a 2nd opinion. i work on trucks everyday and still have people want an other opinion. if we all just went off of what one person said we would still be using steam to get around because the scientific minds thought there was nothing more to invent.
OR maby he just didn't see it and when you replied like a jerk he didn't like it.
you may begin to see the snowball effect now.

?huh,? Why a jerk!. the idea of asking questions and sharing info on here is all about getting as many opinions as possible that's why I stated at end of my reply --" that's certainly the case with my cummins" and didn't say " it was all cummins .. Just a simple acknowledgement of someone taking time to reply and share their findings I thought would of been the normal thing to of done . If I ask for people's experiences on here then I read every reply and acknowledge it whether I like the info or not and whether right or wrong . Thanks for your reply tho.

 

[jollyroger]

I've got 3 5 tons now that I want to do the turbo upgrade to. One of them a wrecker waiting in barstow for some parts to be added before we haul A$$ for home. I realy like all the good info in the thread. Thank you all for the constructive information provided and all the tips and tricks.

It has been a long time since I have cruised the SS site or posted much of anything. And the reason why is what just happened in this thread. I'm just sayin.

 

[dmolson92]

Any updates on the NHC250s with a turbo?

 

[FireFighterHill]

Ive been looking but im having a hard time finding the exhaust manifold. I can find turbos galore but not manifold to use to mount it to the engine.

 

[dmolson92]

Does anyone know where to buy the exhaust manifold? Or have the part number for it?

 

[Vintage iron]

I have access to a bunch of 855 parts. Let me see what I have.

 

[mlwats1@hotmail.com]

I want a turbo but I have a 290 sitting in a wrecked cab over waiting to move into my m816 the 290 had a few tweeks to make the truck a little faster on the road which should make the 34000 lbs m816 a little faster on the road. I hope.

 

[jimk]

Be 6 years soon. Never had any problems.

 

[bcowanwheels]

YOU DO KNOW that adding a turbo to a non turbo engine its going to throw off your air/fuel ratio right. things that are substantually different.
pistons, timming,injectors,cam just for a start. i,ve run big and small cam cummins engines for almost 30 yrs and know them very well. you,d have been alot better off just installing a 290/300 hp turbo preferably a holset. also dont over power the small diffs and trans as all you,ll do is break it. a 290 hp engine needs a 900 ft lbs of torque trans. i run rto 9515 trans behind 290,s on road. also that 250 has a small clutch setup.

 

[jimk]

Lol

 

[bcowanwheels]

LOL GUY run the cpl,s at cummins. running a turbo on naturally asperated hi compression pistons lol on that. turbo pistons are alot lower compression because the turbo compinsates for it. if your just gonna drive the truck around it will work but if you work it thats when it will show up big time

 

[bcowanwheels]

also 99% of the "pulse exh. manifolds are junk and they will leak. get a aftermarket pulse manifold there not expensive and come in a 3 piece set.

 

[Tornadogt]

YOU DO KNOW that adding a turbo to a non turbo engine its going to throw off your air/fuel ratio right. things that are substantually different.
pistons, timming,injectors,cam just for a start. i,ve run big and small cam cummins engines for almost 30 yrs and know them very well. you,d have been alot better off just installing a 290/300 hp turbo preferably a holset. also dont over power the small diffs and trans as all you,ll do is break it. a 290 hp engine needs a 900 ft lbs of torque trans. i run rto 9515 trans behind 290,s on road. also that 250 has a small clutch setup.

bcowanwheels YOU DO KNOW that jimk has been a major contributor to this thread, and is well versed on his combination as well as the combinations of others who have posted on this thread. I maybe a little out of line and may have taking your post wrong, but you should take the time to read all 28 pages of this thread and give him some respect....

over and out..

 

[jimk]

No, I was being mean.

Pretty obvious if you want to improve performance you need to change things, A/F ratio included. If you had extra fuel before then add a turbo you might have to cut fuel back (like my deuce) to keep power and EGT under control. If you don't have extra fuel, like my 5T, adding a turbo by itself does very little. You do get a feeble extra 15psi push on the piston on the intake stroke. That extra air is great for cooling the EGT, pistons and ex valves... Cleans up smoke too. All good for the engine.

The NHC250 compression ratio is 15.8. The Pittsburgh Power site listed c/r for the various outputs. The NHC250 being highest, the lowest about 1 point below (450 HP?) Engines in between about 1/4 point increments. That's from memory and it was a long time ago. C/R is not much of a problem when dealing with adding 15psi at 2100. At 36 or 40 psi, well sure.

We are talking 10-20% more power here. On 240hp (the NHC250 rating) that 50 hp at best. Probably less. I don't think that's gonna make the 5 ton Rockwells cry (they weighing 1200- 1500 lb each). Same for tranny and clutch, in my opinion. There are big safety factors built into these old army trucks, and I don't mind talking a tiny slice out of them in exchange for a few more pony's.

Concerns like the lack of piston squirters are, so far, unfounded, which is why I offered the progress report. I never expected piston problems with max EGT in the 6-700*F range. It's lower tan before. That'll make a few parts happy. Cam flex, slightly higher intake temp (due to no intercooler, 15psi might be 230*F on a hot summer day) , lack of steel top pistons, head gaskets...are not causing problems.

Oh, and the turbo I used is a Holset, as stated earlier.

The only thing I might change at this point is going to a 17 button, instead of the current 20 (27 was stock).

 

[Jared]

Hello,

Nice job on the turbo install. Can you tell me about the exhaust manifold. Either part number or what engines to look for that use a similar manifold?

Regards,
Jared

 

[wcuhillbilly]

Hello,

Nice job on the turbo install. Can you tell me about the exhaust manifold. Either part number or what engines to look for that use a similar manifold?

Regards,
Jared

jared, THis is kind of an old ongoing thread, as for the manifold, Most of us grab a manifold off an 855 cu inch Cummins, this is the civy moniker for the 250,290,300,350,375,400,425 cummins that was run during the 60-early-mid 80s Cummins. the early ones were called small cam and the later were called big cam I II III(late 70-mid 80s. if you find one of these in a junkyard or on ebay they are very similar to the early N14 Cummins. basically you want the intak and the exhaust manifolds... some of the intakes have the water aftercooler. This is a plus if you can stuff it down in there. the stock military manifold will restrict the air flow, especially where these pics show the inlet tube mading some crazy bends to circle around and come into the intake from the driver side. the 855 intake manifold will inlet at the top middle with the crossover pipe (most flatten it out with tubing)and dumps in via a large rectangle. shorter crossover pipe =less turbo lag. Turbo, can be the old dinosaur AR12600(VT50) the HT3B or the 4LHR(schwitzer) I would stick with the later 2 as the VT can be found cheap, but the bearing sleeve(aluminum bushing) is prone to failure if it sits around alot. the later are easier to find parts for as well.
Best thing to do is find a donor engine to rob parts from.. you may luck out and get jake brakes at the same time like I did. That way you have all the parts in one place and a guide to go from.. my donor engine cost me $200 and is basically scrap, but I cant buy the core manifolds, jakes, turbo, and fittings for $200. ( jake25a,25b,425 head cores are going for ^$450 on ebay) Rebuilding the jakes has cost me $300 from Cummins, for the kit,(My solenoids are shot) and some sand blasting tanking etc.. I aslo scored the jake compliant rocker boxes and crossheads(extra wide valve head the jake pushes on) off the donor engine, otherwise you will have to grind the rocker arms like the original poster did to his 818. Turbo,, Call blaylock turbo in Kansas PH620-856-5227 Jim is the owner and is VERY helpful, he really knows his stuff with over 40 yrs of turbos. I got a rebuilt with no core charge 4LHR to my door for alittle over $500. (Side note, Jim has devised a way to mechanically take a Cat up over 500hp while making 6.5mpg all mechanical, with no chips.) By getting the donor engine you may be able to score spin on filter adapters and the parts out of the injection pump to match your new air to fuel ratio by adding the turbo..... im still in theproces of putting all these goodies on my 816 wrecker, but cant wait to feel the added giddyup under my seat with the whoa power from the jakes... Good luck,,

 

[Squirt-Truck]

A/F ratio on a diesel???
Can someone help me out and explain that comment?

 

[Jared]

Thanks Wcuhillbilly,

I believe I've found the exhaust manifolds from the NHCT-270 conversion. Found the parts catalog on ebay and started searching the internet. I think they called this conversion for a NHC-250 a "smoke kit".

Regards,
Jared