ViperSBT

OK, showing my tender green underside, what is valve float?

I have definitely noticed that I use practically no pedal anymore. I haven't been out hotrodding it, and all the smoke I used to make has gone away so I don't have that fun right now, so I am being conservative in my driving, especially with what my mileage appears to be doing.

So, is it safe to say that I am getting more out of the engine at 3/8th throttle than I did at 3/4 throttle, I should be getting better mileage? Again, unless my fuel gauge is broken, I am going to average something close to 20MPG including all the city driving I do... That just doesn't seem possible... I wonder if I could have fixed a prior problem when I was in working on the pump???

My solenoid boot is tattered and I am waiting on a new one, but when I took it apart the spring/plunger may not have been in place? Would my truck have even been operating without that working correctly? Would it have impacted the performance?

This is another question I have though, while I was in the pump I looked at doing the "Secret Governor Lever" adjustment. When examining the existing condition of this, the governer lever travels completely underneath the CAM plate! How bad is this and what is it doing to the truck? I couldn't adjust it as I couldn't get the **** screws off the back of the pump. I am getting some offset screwdrivers to tackle this job, and figured I would do it this weekend when I replace the boot on the shutoff solenoid.

ViperSBT

OK, my fuel gauge must have gone whacky... After running through the tank, and having some fun at the same time, my calculations still put me at 16MPG. It is odd that I had 300 miles for the first "half" of my tank and only 200 for the second "half" according to the needle.

I would still like an answer on this:

Paul Winey

viper:

Valve float is when the valves don't fully seat due to high rpm and too little valve spring pressure to close them. It's only bad when the valves hit the piston . Regarding the governor arm, I wouldn't do any hot-rodding until you get it fixed. If you can't get the back off of the pump then you may need to slide the fuel plate back. Remember to hold the fuel solenoid arm up when making the adjustment as it's not accurate if you don't. Get ready to skin up your knuckles and arms. A mirror helps too.

ViperSBT

Thanks for the warning. I will get on it soon, I am heading out of town, so the truck gets a week off...

MCummings

Valve Float can be several things...

My definition of valve float is : The cam loosing control of the valves.

Too high of RPM, to much lift, a rocker with too much ratio, or too weak of springs.

The very begining of valve float is where the valve will fully close, but because of one of the reasons above, the rocker, or pushrod, or lifter does not follow the cam down, and although the valve closes, it hits the seat so hard, it will actually bounce, and can bounce several times.

Valve float can also be where the cam starts to push the valve open, and because of too much boost/RPM/or too weak of a spring the valve will open much farther than intended and some part of the valvetrain will actually leave the cam and the valve will open several thousands of an inch too far.
This is also very bad because instead of the lifters riding smoothly on the cam, they will will jump off, and land on the downslope of the cam. Our Cummins have solid lifters, and are not forgiving of this situation, the constant hammering of the valvetrain from valve float will quickly kill your motor. You can usually feel major valve float by a momentary loss of power under high boost and high RPM.

A '97 12v running 35PSI and 3,600RPM will have valve float, however, a '98 12v can run the same boost and same RPM w/o valve float.

A '99 24V can run about 50PSI before valve float. Anything over 50PSI, and a mild cam will cause the valves to kiss the pistons. Although this may not kill the motor, it definatly hurts top-end power.

My truck with a Stage 1 cam will float the valves over 2,800RPM and 55PSI. I can feel it as a surging that is hearable out my exhaust, and I can see the boost gently flutter by about 3psi.


As far as getting more out of the first half of the tank vs. the last half...
It's a ploy by DaimlerChrysler to make us feel better about our fuel mileage. My truck sits above the "F" mark for about 75 miles, yet goes from 1/8 to "E" in about 30 miles.
If you filled the truck up, and within 10 miles the fuel gauge came off of "F", you'd feel like the truck got bad mileage.

I think it's normal.


Sorry for taking so long to get to you. Seems I might be changing jobs slightly...

Merrick