Champion 720R, black smoke when accelerating suddenly

[Southbus]

Cummins 6ct 8.3 12 valve , 173hp
The Story of this old Six cee tee
This engine ran erratically, cylinder 6 was dead and always smoked heavily when accelerating.


Observations:
When disassembling, note that the liners had cavitation problems, especially that of cylinder 6.

Work
I put new liners, new piston rings, new metal connecting rod and bench (STD), these had very little wear but taking advantage of the instance I decided to change them. The injectors were restored at a diesel injection company and the cylinder head was also overhauled and they put new guides and seals along with grinding the valve seats.
The long-awaited day.
Yesterday I started the engine and it has a more even sound and all the cylinders work although, after an hour of operation I can observe two situations.

1- When accelerating quickly, black smoke is produced, In practice this black smoke is seen every time I change gears.

2- The idle is at 730 Rpm and I feel that there is some kind of oscillation perhaps caused because at this level of revolutions all the cylinders do not work evenly.

Obviously I cleaned all the fuel lines, and I put in new filters.

The only thing that did not receive service was the injection pump (Bosch)

I don't know how to check if the timming is at 11 ° as the manual says.

What do you think about these anomalies in this newly tuned engine?

I take this opportunity to thank everyone who advised me on this my first engine adjustment and it has really been gratifying to revive this little monster.

Cheers!
Cesar

 

[DB2]

Glad she’s running again. I can’t help with the timing but did you do anything with the turbo? I’m assuming new air filters? Black smoke equals unburned fuel. What altitude are you operating at ?

 

[Delmer]

Did you remove the timing gears when you did the work you mentioned?

Can you get a video of how it sounds and looks when accelerating and blowing black smoke?

Could be perfectly normal, the dead cylinder was dragging down the turbo boost and holding back the fuel possibly. Search "spill timing bosch injection pump" for the procedure.

 

[Fatgraderman]

Boost leak maybe? If you’re comparing it to newer stuff, it’ll smoke a bit compared to them. Is the turbo compressor wheel spinning freely? If it had a bit of antifreeze going through it, it could have some chunks in it. Any exhaust manifold leak will compound issues. We always had quite a time getting the old exhaust manifold to seal up again.

 

[thepumpguysc]

To check the timing its easy..
U see the plunger under the pump.?? It has a bump out on the end that will slide into a hole in the cam gear..
once the bump out falls in the hole(TDC) the pointer in the gov will/should b dead center in its hole.. There is a tool u screw into the gov. where the pointer is and it’s called an A-B lite..& runs off a 9v battery..
When the pointer comes around it hits 1 side of the tool and lites up either the A or B lite.. keep turning and BOTH LITES LITE UP.. and that’s your degree mark.. 11*
The pointer is set inside the governor by your local fuel shop
U can check/set timing 1st and then move on to turbo..
Good luck..

 

[thepumpguysc]

The top screw on the back of the gov is the low idle screw..
The 2nd screw is the low idle surge screw.
Hope this helps..

 

[Coaldust]

DB2 mentioned the turbo. It’s a best practice to at least change the center cartridge. You could check boost. A reman turbo would be a good idea.

I wouldn’t worry to much about it, yet. Put it to work and get those piston rings broke in.

 

[Southbus]

I want to sincerely thank all your advice and explanations, the truth is that it is the first time that I uncover an engine of this size but I think it is simpler than I thought. I put the cylinder 1 in TDC with the help of the timing pin, then uncover the big nut of the Governor of the pump and take out the small tool that lives there, I turned it over and inserted it in the same hole and it fits perfectly on the tooth of the shaft there is inside the pump.
Is that enough to check that the pump is exactly synchronized and injecting the fuel at the right time?
For my taste the engine sounds very good and some people have told me that the smoke is little and maybe normal for a year 88 engine with mechanical injectors (not electric).
Then I will record a short video with audio where you can have your own conclusions.
I did a temperature test, with the help of a laser thermometer, in the exhaust outlet of each cylinder, where the exhaust manifold is born and I have:
257 ° F on cylinders 2-3-4 and 5
160 ° F at cylinder 1
196 ° F at cylinder 6
This measurement was taken with the engine idling at 734 Rpm after 15 minutes of running.
This may explain that little that slightly uneven gear is idle.
In constant work and more revolutions the march is more even.
Cheers
Cesar

 

[Southbus]

Dear friends, I want to thank everyone who took the time to give me advice and knowledge to be able to repair the engine of my old school motor grader.
The grader just finished a 4 day job and the engine has worked perfect, just a little smoke and maybe I'm exaggerating a bit, I send you a video so you can have your own impression.

You should know that this forum has been fundamental to be able to repair this old machine, this network of mechanics and machine owners is incredible, there is a good mood and desire to share knowledge and I am also now in love with American machines.
I have some desire to import a used motor grader from the United States although I know that it is a matter for another forum, for the moment I will continue with an oil change in the transmission and I have created another post and I am already eager to read your words to proceed.
I send you a hug and I thank you very much.

Cesar