Cummins NTC-350

Messed with the truck some again today. Still dont have the tach fixed. It does no want to idle right. Even sitting there it will speed up and slow down. It won't take off on its on but probably fluctuate a couple hundred rpms. When the clutch is pushed in it instantly speeds up, the. When driving it around it will take about 30 seconds for the rpms to slow down to almost an idle.

My dad and I are thinking the problem lies in the pump. I talked to the previous owner again today and he said that right before he got the truck, the pump was not changed, just the cluster gear that drives the pump.

We also figured out that it has been at least 12 years before it the truck has really been used. It hasn't been registered since 2001 and the previous owned said he was lucky to put 500 miles on it a year for the 7 years he owned the truck. (He has an excavator and a lowboy and would use the truck to do side jobs). We are thinking it maybe necessary to get the pump looked up and cleaned up, as well as the injectors.
 
Small cam

Slow returning to idle could be restricted fuel return line.
This is a pressure /time fuel system. If return is retricted
Pressure stay up until fuel is used up. I would also try setting
overhead and see if smoke clears up more.
 
That makes sense, never thought of restricted return causing a slow return to idle.

Like stated before, we've never had a big Cummins before, only mechanical Cats. So we're going to have to learn how to adjust injector lash.
 
Well I've decided to get the pump and injectors looked at to be 100% certain they are all working properly. It was very interesting and a new learning experience tearing the rocker boxes, jake boxes and injectors out.

Buffed a small corners of the cab out and the paint came back better than expected. I could see my reflection in it! This thing is going to be so sweet whit the motor running properly and the paint shinny.
 
I be completely honest with you I don't really know for sure. I was told by an old timer that worked them and said they could make north of 600 horse.

As far as I know there isn't much different between a big cam and a small cam. Besides obviously the physical size of the cam shaft.

Either way it should be a pretty fun little truck!
 
Did you run the overhead? There shouldnt be any injector lash, theyre top-stop injectors IIRC.
 
No I did not run the overhead before pulling the injectors. I was going to but the truck needs to be ready the first weekend of June, and I have a ton if work to do to it. So the injectors and pump are going to a diesel shop in PA, Antrim Diesel, Tuesday.

My dad and I figured that the truck hasn't done much in at least 12 years so might as well get them all checked out. Plus we don't really know how to set the injectors, yet!
 
Someone that has a manual or quickserve will be better help, but again IIRC to set lash / injectors: start on lets say "A" (could be marked vs1-6), set valves on cyl #1 if its on TDCC and you set the injector to zero lash (5in-lbs) on the cylinder next on the firing order. That engine should be set on the inner base method. Its been over 5yrs since Ive touched an 855 so take it all with a grain of salt if you will!
 
A small cam will not have top stop injectors in it, there is a different process for setting them.

You will not be able to get the HP out of a small cam that you can a big cam, the timing is the biggest difference, the small cam will burn up before you get anywhere close to the power of a big cam.
 
Yea I know its a different process, OBC. But I didnt have a book in front of me to match up his cpl# to the injector/pump setup. Top stops are the easy ones to set.
 
You can go in the same order, for example if you are at the first "A" you would set the valves on #5 and also the injector, bottom the injector completely out, back it off a couple of turns and set at 48in/lbs.

Its not much harder, just have to have a good torque wrench.
 
My dad has got a friend that knows a bit about this motors that will be able to we the injectors when we get them back.

Power isn't a huge concern at the moment, getting it running correctly is. It anymore power is desired beyond what this little 855 is capable of, a yellow motor will take its place!
 
SmokinCAT said:
You can go in the same order, for example if you are at the first "A" you would set the valves on #5 and also the injector, bottom the injector completely out, back it off a couple of turns and set at 48in/lbs.

Its not much harder, just have to have a good torque wrench.
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Good to know, its the finer details that fade away after a few years :lolly:

I wouldnt drop a Cat in it just yet, lots of little tricks to wake it up and if youre looking for big power you will have problems with everything else in the driveline.

Did you happen to check fuel pressure to see if the pump was doing any good before? Depending on what injectors are in there, might have the pump shop set it up for a little extra (180-190psi IMO).
 
RockinRam96 said:
Not a bad looking truck, whats in it for a motor? 359 or 379?

I can never tell with these Peterbilts, my dad had two of them, one 359 and one 379. The only way I know how to tell the difference is the headlights. But I also know you can get 359 headlights for a 379, so that theory is thrown out the window.

Don't get me wrong I like Peterbilts but it seems like everyone wants one or has one that is tricked out. I'll stay with the KWs for now. But to each his own.
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Easiest way to tell is the air cleaner boots go through the hood on a 359 and into the cab on a 379.

Sent from my DROID RAZR HD using Xparent BlueTapatalk 2
 
JWhite said:
Good to know, its the finer details that fade away after a few years :lolly:

I wouldnt drop a Cat in it just yet, lots of little tricks to wake it up and if youre looking for big power you will have problems with everything else in the driveline.

Did you happen to check fuel pressure to see if the pump was doing any good before? Depending on what injectors are in there, might have the pump shop set it up for a little extra (180-190psi IMO).
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Oh no, a CAT wont be going in this truck any time soon, if ever. As of right now the whole driveline, we are going to do the basic driveline work (u-joints, slip joints, and an oil change in the rears).

The pump was completely sealed up still, so it has never been turned up at all. The pump shop will be well aware of the intentions of this motor and truck.

As far as end power goal is concerned, I don't really have one in mind. To be honest, if I can get it running correctly and get it to pull consistently week in and week out in the street semi class with no breakage, I will be happy. Now I know in some places a "street semi" is a lot more than what this little 855 can put out, but around here it is literally guys with road tractors pulling. Aside from my father and he doesn't have much invested.
 
Just heard back from Antrim Diesel. All of the injectors cleaned up and tested just fine. But the pump did need to be rebuilt. The guy that worked on the pump said that it showed signs of normal wear but did need to be rebuilt.

He also set the rail pressure to 200 psi and bumped the RPMs up to 2,200. I can't wait to get this motor back together now and get it running.
 
one thing i would recommend doing is putting a holset turbo on it. from the pictures you posted i seen it still had the vt-50 turbo that cummins made and there known for pushin oil around the seals. a holset turbo would also gain you some power plus better insurance
 
heins said:
one thing i would recommend doing is putting a holset turbo on it. from the pictures you posted i seen it still had the vt-50 turbo that cummins made and there known for pushin oil around the seals. a holset turbo would also gain you some power plus better insurance
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To be honest I have no clue what model charger is on the truck right now. I know it is quite a specimen. I know it is a Cummins charger not a Holset charger. When was Holset established by Cummins?

An HT60 is in the future. Until then a pyro will be installed and I will be watching at it intently.
 
I have not a clue when holset and cummins got together. I do know that some other the later small cams had holset turbos on them so im guessing mid to late 70's
 
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