Truck Repair: L-10 running rough, cummins l10, pin hole

Question
Thanks for your reply. I still have some questions to ask.

(For the pin hole leak) Is the hole suppose to be there? I welded mine shut.

Also, if I am going to replace the injectors, do I have to drain the engine oil?

When putting the rocker levers and injector back in, what are the valve and injector adjustments (Engine #34663542 310 HP)?

Do I need any special tools to remove the injector?

Are their any o-rings when I take the injector out and do they need to be replaced?

Thanks for your time and consideration. I would appreciate any suggestions.
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Followup To

Question -
I have a '92 Cummins L10 STC engine.

It idles fine but as it give some rpm it gets rougher. The engine seems like it has lost a great deal of power.

I decided to check the engine out and removed the valve cover. I took a look around and found that the oil manifold that goes to each injector had a pin hole leak around the #1 and #2 injector. I removed the manifold and welded the hole closed. It's kind of weird that the pin hole was clean. Looked as if someone drilled a hole.

I also found that the rivets that are on top of the push rods were missing on three of the them.
Is this going to cause any problems?

The engine does feel like it has gained some power but does not run like before. I am thinking that one of the injectors maybe bad. I am thinking about getting a laser pointed temperature sensor to check which one might be bad.

I have never worked inside the engine before. Is it difficult to replace an injector? Could you tell me a general overview on how I would replace one. Thanks.




Answer -
The hole was probably put there to bleed air out of the manifold.
Take all 3 adjusting loose.turn engine to cyl to replace injector.Remove pushtubes & flip rocker lever over because the exhaust is covering the inj hold down bolt.The bolt is a 12MM 12 pt socket.

Answer
You dont have to drain the oil.There are 2 special tools you need,A "T" torque wrench & a tappet tool.The hole was to bleed out the trapped air in the oil manifold to keep it from white smoking at start up.L10/M11 STC engines still adjust the old way A-2&5,B-3&4,C-1&6.Valve clearance is 0.014 int & 0.027 ex.
        MARK          Valve          INJ
         A          2          4
         B          4          1
         C          1          5          
         A          5          3
         B          3          6
         C          6          2