My '89 9670 build


For you lovers of the Class 8's and bigger.

Golden Jubilee
Golden Jubilee

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Joined: Thu Dec 27, 2012 12:45 pm

Location: Canada's left Coast

Post Thu Oct 19, 2017 2:17 am

Re: My '89 9670 build

Do you like the PT Cummins system?
I would rather have tools I do not need than to need tools I do not have
No good person will ever go unpunished!

Golden Jubilee
Golden Jubilee

Posts: 2906

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Thu Oct 19, 2017 7:55 am

Re: My '89 9670 build

nikkinutshop wrote:Do you like the PT Cummins system?

The only thing simpler is the unit injector Detroit used. The PT is reliable and easy to work on. The Bosch type injection pump that Cat uses has much more control of the timing as engine speed increases.
Each has its advantage and drawback. I think the PT is a good middle ground between Detroit and Bosch/Cat type.
On a Detroit, there are a lot of mechanical adjustment to make the whole engine work as one unit, no cyl working harder or less hard than the rest. On the PT system the injectors are flowed and set on a test stand and should hold that adjustment though out the injectors life. The only adjustment on the engine is the rocker lash.
The Bosch system is very complex but very reliable, the problem comes after a million or two miles it is very expensive to overhaul.
I've found this helpful
https://www.youtube.com/watch?v=KzuwdxEJfQA

Golden Jubilee
Golden Jubilee

Posts: 5802

Joined: Thu Dec 27, 2012 12:45 pm

Location: Canada's left Coast

Post Fri Oct 20, 2017 6:00 pm

Re: My '89 9670 build

I have had experience with Detroit Unit injectors and even some time rebuilding the older DD mechanical governor systems. I was present for one rebuild on a Cummins PT and I was the guy handing the tools to the real mechanic who did the work. One of the sound good engines was the Cummins 903 V8. the company had about a dozen of these monsters. I remember the 903 having problems but I don't remember very much about that, either. I have been retired for nearly 14 years.
I would rather have tools I do not need than to need tools I do not have
No good person will ever go unpunished!

Golden Jubilee
Golden Jubilee

Posts: 2906

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Fri Oct 20, 2017 6:11 pm

Re: My '89 9670 build

The Nine o nothing had a much better rep down under and marine than it did in N/A trucks. I am in inline guy and never liked V engines of any kind.
The Detroit injectors are very simple and goes a long way to explain why the 2 strokes had such a good reputation. As long as you have rail-pressure at least some of the cyl will fire, regardless of the rest. The engine may not run on all 6,8, 12 etc, but will get you home.
The PT system is a little more complex, and inter-dependent, but still is simple enough for someone like me to work on in my yard.

Golden Jubilee
Golden Jubilee

Posts: 5802

Joined: Thu Dec 27, 2012 12:45 pm

Location: Canada's left Coast

Post Fri Oct 20, 2017 7:21 pm

Re: My '89 9670 build

The introduction of DDEC to GM Diesels made a big difference in performance and improved economy. Diagnostics was better, but, that sneaky DDEC like to cover for a failing cylinder and sometime it was difficult to tell there was a problem with the old hands-on diagnostics. That is, unless a person noticed that the header was cooler on one cylinder. I bought a RAYTECH laser temperature gun. A quick exhaust manifold scan, at the ports, could often direct any more diagnostics. I like the RAYTECH for air conditioning diagnostics. Now, my wife uses the Raytech to check the roasted turkey and the temperature of the jam she is making.
I just checked my self to see if there is any life left and I am at 97F or 36.5C. I AM ALIVE! I AM ALIVE!
I would rather have tools I do not need than to need tools I do not have
No good person will ever go unpunished!
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