Cylinder head wear...

[Hammerhead]

(07-06-2017 )Rawze Wrote:  Mr. Hag has made some pretty good observations towards oil flow and intake rockers. He showed me a about a month ago the difference between setting the intake rockers to 0.014" and to 0.015". the oil flow is quite a bit better on the intake rockers when they are set to 0.015" and it does not seem to effect fuel mileage in any measurable way on them. I am still up in the air on it, but the oil flow is significantly better when they are set this way. I am going to set my own intake valves at 0.015" next time I do my overhead and see if the fuel mileage is effected on mine.

I would be shocked if even you will be able to see an actual fuel gain/loss with an extra thou Rawze. Back in racing days I played with valve timing a lot, and the real gains were only noticeable in the extremes; perfect atmospheric conditions to below sea level DA, and high altitude in the mountains.
During dyno testing there was no discernible difference with as much as 0.005" difference, and in high altitudes we actually made gains running an extra 0.015" (intake), but this was NOT forced induction. Our theory on the altitude gain was the delayed opening created extra vacuum force upon opening and the thinner air responded more to the velocity since the flow capabilities exceeded the density.
I'm quite confident that the turbos forced induction would wipe out any perceptible difference.

Hard to imagine that 0.001" would make that much of a difference on the oil flow, but then again I've never looked into the metallurgical composition of the valves and the amount of thermal expansion that takes place. If the expansion is enough that a 0.001" difference quantifiably increases oil flow, one can only surmise that Cummins tolerance spec is too close. I wonder if the exhaust valves are too close as well?
This also really highlights the lunacy of C stating overhead adjustments not required for 500k miles doesn't it?
I would think due the torque loads demands of my job, I would certainly benefit from the extra clearance if this is the case. I doubt the fuel economy difference for me would even be calculable, but longevity certainly is. I will also be trying this.