JAKE ADJUSTMENT ON ISX

[Hammerhead]

(07-02-2019 )Rawze Wrote:  I have seen something related happen a couple times. I think it even happened to hammerheads truck once, put him in a panic.

Sometimes, the rocker shaft will slip just a bit, or get twist in it when tightening it. detent clearance will be too low, making you think something is wrong. Only trouble, is that it will be messed up on only the front 3 (or rear 3 cylinders) consistently,.. or the problem will progressively get worse between cylinder 1 to cylinder 3, or 4 to 6.

If re-seating it a couple times and re-checking does not solve it,.. then head is problem.

Yeah, serious panic. Thought I had serious valve recession and was thinking I was replacing a head, unplanned and seriously early.
Don’t ask me how it happened, but the jake measurements progressed from good to worse front to back on the front rocker shaft. I pulled the front 3 injectors and looked at the valves and seats with my boroscope I shared the pics with Rawze, and he confirmed what I was seeing, that all valves and seats looked fine, no visible signs of excessive wear, so I pulled the front rocker assy and everything appeared fine. I also measured every valve stem and they were all measuring the same, so the difference didn’t make sense. I put it all back together and remeasured the valve clearance and all was “normal”.
The resulting theory is somehow the rocker shaft torsionally rotated slightly, caught by regular overhead adjustments and measurements. When these shafts were put in, I used straight torque, not torque plus angle and I used the “old” value. That is the only logical conclusion we could come to. If you’re going to use straight torque in place of cummins torque plus angle, use 90 ft/lbs. An old video suggests 74(?), and that was what I had used.