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b61fred

cummins big cam 3 overhead setting

7 posts in this topic

can someone help me with the proper procedure for setting the over head on this engine, I need the clearances for the intake and exhaust and jake brake. I need the torque specs for the head bolts also, It is a ntc400 1983 engine. Thanks

Morgan

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Thanks for the help Pawel! I searched for a while and found the information on another web site. Got my gaskets today and hope to have it back together this weekend.

Morgan

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The valves set on .011 and .023. The overhead on this engine is set by the inner base circle method, and is confusing, if you are not used to doing it. Cummins did offer a shirt pocket sized chart, in the form of a treasure map, of where to go and dig next. It is confusing in that the valves are set on one cylinder and the injector on another. there is a lot of information on the net, some of which is dangerous. Buy or borrow a service manual. I have always set the Jake with the engine running, after going through the overhead. When you get that far I'll try to talk you through it.

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I refuse to try to help on a cummins over head because it is too easy to misunderstand and too muc h damage can be done. First thing i will say is find the cpl and then go to jake brake.com and find the jake brake install instruction and they at one time told you how to run the over head for that cpl. Dont mix the procedure for oter base with inter base. That is for different cpl injectors.

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Honestly, I didn't find it that difficult. I did it for the first time a couple months ago.

I used the torque method to set the injectors. Torque method and indicator method are quite different. (valve clearances as well) Have to do it on the firing order. 153624. Use the timing marks on accessory drive. ABC, should be. Turn the engine over by the accessory drive, its easiest. Way I did it was 1 do valves at .011 and .024 I believe, and 72 inch pounds for injectors (if not mistaken). Then same for 5 ect ect. Thats how I did mine and it runs very well.

As far as Jake, do it with engine running. as soon as you feel screw hit rocker, back it off turn and a half.

Hope it helps.

Bob

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Head bolt torque specs stick in my mind at 300 foot pounds. I used a torque multiplier, 4:1 set wrench at 90lbs equals 360 minus 10 to 15% for drag...

Rocker boxes are like 75 foot pounds, same as Jake parts.

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