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Junior Member
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15 Posts
Discussion Starter #1
About a month ago now I bought a 1973 Kenworth W923 with a Cummins NTC-350 small cam 855. I wasn't really looking for a truck but my father and I went to just look at it and I had to have it. The truck is 100% complete and as should be from 1973. There was also original paint on the frame from 1973. The paint on the hood and can is also in very good shape, a few chips here and there but I am pretty impressed being 40 years old. The interior is all complete, not missing any gauges or switches. It does need se attention but it isn't terrible.

Now for the motor. Neither my dad nor I have had experience with big Cummins motors. My dad has been a CAT guy forever and this is the first time we have been into a big Cummins.

When I brought the truck home it smoke really bad, white smoke. So we assumed it was the injectors. We tore the whole overhead apart, sent the injectors and fuel pump out to be tested and rebuilt. The injectors tested out fine and got cleaned up. The fuel pump needed to be rebuilt, so that was rebuilt. Put it all back together after searching and talking to a lot of people about the correct way to set the over head. There was no change in the amount of white smoke, so we ran the overhead a 2nd way. Still no change.

The first two times we set the over head we followed the firing order and the timing marks on the accessory drive, and setting each injector/ valve combo by the firing order. We had talked to a couple shops and old timers and was told the cam may be worn causing the bad white smoke. The 3rd time we set the overhead, we used a dial indicator to find where the cam follower was resting on the cam and tracked it all the way to the top of the lobe on the cam. Then we set the injector at the top of lobe to 70 in-lb. this seemed to be the best method yet. We have one more idea of a method to set the injectors we are going to try today.

This truck is pretty much a dream truck for my dad and me. My dad has wanted an A model Kenworth and since my dad bought his first truck I have wanted a big truck. It is going to be a continuing project with hopefully a show truck/ pulling truck. Right now it is going to be a puller, when I had the fuel pump rebuilt, the rebuilder increased the rail pressure to 200 psi from 160 psi.

I am really looking for help and info on this old Cummins. I am really hoping the cam isn't bad but all signs are pointing that way. Any help will be greatly appreciated.

Thanks guys and enjoy!
 

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Aimless Wanderer
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929 Posts

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Junior Member
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15 Posts
Discussion Starter #5
Yeah and service brakes on the rear drive. the only parking brake is on the front drive. This truck will never work again. Unless some day I can afford a 2.6 puller, it will only work to haul that around
 

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Junior Member
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15 Posts
Discussion Starter #6
Man I look like a newby to forums with all the post I have in my own thread...

I am not putting a Cat in it right now mostly because my wallet won't allow. But my dad has a 3ZJ, 3406C in his work truck at the moment. He is going to buy a 4MG, 3406B and rebuild to make 600 horse for his work truck this coming winter. Then the 3ZJ is going into my Kenworth.

I also would like to keep the Cummins because it is original. And this truck is about 100% complete!
 

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Junior Member
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15 Posts
Discussion Starter #7
Well was able to get the truck out and drive it around a little bit. Ran it for maybe half an hour or so all together. The water temperature got up to about 170 to 175 and the white smoke at an idle was all cleaned up. There wasn't even a wif if white smoke in it, accelerating no white smoke. I am very happy with the result. I was hoping heat would help solve the problem, but wasn't going to get my hopes up.

Here's a little video:
http://s1166.photobucket.com/user/RockinRam96/media/1973 Kenworth W923/IMG_1867_zps9351a343.mp4.html
 

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Senior Member
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2,555 Posts
That looks like a good solid old truck. white smoke is pretty common in the old NTC s, a valve set might help to clear it up some, but it is pretty much the nature of the beast.
 

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Junior Member
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15 Posts
Discussion Starter #9
Finally got it out and drove the truck around a little bit last week. Water toe rapture got to about 160 degrees and the smoke was about all cleaned up. I think it runs very well especially when it gets some heat built up in it.

Did a bunch of polishing on the paint this weekend. Started off with a buffer and rubbing compound, them moved to using polishing compound by hand. Next will be to wax the whole truck. I think the paint looks good. Especially for being 40 years old. There are a bunch of dull spots I the paint, but that's to be expected. Over all I am happy in how it is pushing out.
 
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