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Cummins 335 circa 1967

37K views 23 replies 7 participants last post by  whskyfan 
#1 ·
What can you do to an older cummins 335? I understand this would be a fairly early 855 small cam. What are the limitations and how do you spot updated or upgraded motors? I am shopping an old truck and am looking for pointers and if I buy what I might look into doing to it.
Kevin
 
#2 ·
The NTC-335 had a T-590 turbo on it. Also no intercooler in place of the intake manifold.

Some of the earlier and high altitude 855’s ran a T-50 turbo but that’s rare on 335’s. The NHCT-270-HT earlier 855 is sometimes mistaken for the 335 but it had the T-50 turbo.

The NHC-250 was also an 855 but non turbo. Some people upgraded these with turbos.

I have a 1971 359 wide nose Peterbilt NTC-335 that I upgraded to a NTA-420 with a Schwitzer 4LH turbo and side mounted coolant to air aftercooler. Injectors, pistons and cam timing also were changed. I ran the cam timing at 43 on that motor, smokes on cold start but cleans right up when warm.
 
#4 ·
The truck I am looking at is a 67' Peterbilt 351, twin sticks, hendrickson. I like the 358 and 359's as well. So is aftercooling these very hard? Bolt on the cooler parts and some plumbing I would assume.
 
#5 ·
chris142 said:
Whats this I hear about the tapered crank? I hear they need to go away? Can you easaily identify one in the truck?
All of the old 855 crankshafts have a taper the front hub mounts on. The hub is small and the harmonic balancer or viscous vibration damper bolts to it.

It’s famous for not being easy to pull, especially when rusted.:damnit

Cummins has a hydraulic puller for that hub. I made one out of 1” AR plate with SAE bolts going on the hub like the dampener. Than a huge 1 1/4” SAE bolt in the middle to center on the crank. 1” impact on that usually does the trick.. Than NeverSeize it going on so the next time it’s easy..
 
#6 ·
kblackav8or said:
The truck I am looking at is a 67' Peterbilt 351, twin sticks, hendrickson. I like the 358 and 359's as well. So is aftercooling these very hard? Bolt on the cooler parts and some plumbing I would assume.
Here’s some picts from the service manual. Not hard, just goes in place of the intake manifold and one hose comes off the back of the block, the other up near the top front.

It was available in a kit but now I don’t know..:shrug:
 

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#7 ·
Lowboy said:
All of the old 855 crankshafts have a taper the front hub mounts on. The hub is small and the harmonic balancer or viscous vibration damper bolts to it.

It’s famous for not being easy to pull, especially when rusted.:damnit

Cummins has a hydraulic puller for that hub. I made one out of 1” AR plate with SAE bolts going on the hub like the dampener. Than a huge 1 1/4” SAE bolt in the middle to center on the crank. 1” impact on that usually does the trick.. Than NeverSeize it going on so the next time it’s easy..
Oh ok. So it's not a strength problem just a maintenance problem. I'll cross that bridge when that time comes.
 
#8 ·
chris142 said:
Oh ok. So it's not a strength problem just a maintenance problem. I'll cross that bridge when that time comes.
The maintaince, front main seal and strength problem is with the front aluminum motor cover. That cover is also the total front engine mount behind the crankshaft hub. They will break after a million miles or so..

You can build a new saddle to go on the cover but a new front cover for the small cam is a couple thousand from Cummins England.. :bling: :sofa
 
#10 ·
There have been cases where the taper crank snouts will break off. This is usually only the case when the damper is bad and the operator/mechanic didn't know or didn't replace it. The snouts can also be an issue with a lot of belt driven accessories or when the governor has been turned up and you are running more than 2100.

Ya, the aftercooler is just a bolt on. Couple hoses, some new intake gaskets and you're done. I don't think the kit is available anymore, however all you really need it the aftercooler. The crossover pipe and other plumbing can be built easy enough.

We've got a NTCC-335 in an W900 end dump that's still kicking. It still gets run a fair bit, the driver still seems to like it so we keep it around. Bumped the timing a bit and tuned up the AFC and changed down one button. Runs pretty good, not the most power in the fleet but it does what it needs to without an issue.
 
#11 ·
the335s were notorious for cracking crankshafts if the damper went bad. i remember several needle nose petes with them and they had no heating or should i say cooling problems. istill has aftercoolers for a ebgine that old. kind of doubt if cummins still has aftercoolers laying around for a 335.
 
#12 ·
I thought the 335 Cummins was the smaller 743cid displacement ?
 
#14 ·
Can't find the small bore 335 in the Cummins manual but they could have done a mod fuel rate for a limited number of engines.

They had a big bore (5 1/2x6") production motors at 250 & 230 HP, NH230/NH250..
 
#16 ·
I just tried this with wide angle lens. My big greasy mitts from a long time ago show up also. :damnit My father did the underline when we were deciding how far to go on the re-rate in the shop one day.

Cummins had so many hp and displacements that were called "custom motors" it's hard for me to remember.

If this works I'll post the other pages.
 

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#18 ·
whskyfan said:
Let me see what I can find out. Could be a NTO, a higher horsepower version of the NTO 262. As you said, Cummins made a lot of different engines. The man I work with was with Watson and Meehan for 30+ years, let me talk to him and see what he remembers.
Good to hear, I didn't know any of the Watson Meehan guys were still around.

I have a rack of their update manuals here. IMO, when it went to Cummins West it was downhill from there.

Here's one on the crankshaft revision of the old long shaft air compressor, we had a thread on it not long ago.
 

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#19 ·
Here's the engine data I have from my 70's vintage manual;
 

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#20 ·
the alum front motor mount was a weak point. any good machine shop could lnock off a steelmount if they had a alum one for a pattern. the 335s were touchy with good vibration dampers. a neede nose had enough radiater for a 335 but no one wanted a needle nose in the late 80s.
 
#21 ·
fred43 said:
the alum front motor mount was a weak point. any good machine shop could lnock off a steelmount if they had a alum one for a pattern. the 335s were touchy with good vibration dampers. a neede nose had enough radiater for a 335 but no one wanted a needle nose in the late 80s.
The front cover aluminum casting included the mount stub that rode in the saddle. The casting had oil passages for the oil pump bypass and piston cooling right side oil galley. Also had the accessory drive front stub bearing and is about 18" across with mount holes, dowel holes and accessory drive seal.

If it was practical to machine it Cummins would have done it from the beginning. We could buy one much cheaper than we could machine one in our own shop.

The Cummins 335 was no more likely to break crankshafts than any other inline 6 cylinder diesel. They first used a jell filled dampener which after 4 or 5 years of age the jell would turn solid and vibrate the motor and mounts to destruction. Later they improved the jell so it would stay soft much longer.

Anybody that changed the dampener when required had no problems. I have over a couple million short trip miles on my 335. Has the original block and standard crank from 1971 and only one front cover. 4 or 5 dampener's tho.
 
#23 ·
Cummins had more motors on the road in that era than anyone so out-dated stories and rumors abound. Mostly CB driver to driver BS tho...:rolleyes:
 
#24 ·
Lowboy said:
Here's the engine data I have from my 70's vintage manual;
Looks like there was 2 small bore 335's. The NHHRTO-6 and the NRTO-6. From what I found out the small bore 335, as well as other small bore engines, were only out for a short time because of the duplication of ratings with the big bores. That and the fact that the big bores all had oil sprayed pistons. The only small bore I am aware of with oil spray was the 320.

Yeah, I think Ralph is just about the only one left from Watson & Meehan, he's 83 and still builds motors 3-4 hours a day.

Great manuals you have there, take good care of them. And if you ever decide you want to part with them let me know...
Jim
 
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