I posted this same thing on Cumminsforum but hoping somebody has discover this in the past. This VE came off a BlueBird school bus. the delivery valve seats seem to be ground flat in one spot. It seems about .005-.010'' of material removed, also somebody ground these seats very accurately but not consistant. All six are close but not exact. Why would somebody do this? Was this actually a Bosch or BlueBird modification? Needless to say these things will leak.

 

Yes, those are a stock/OEM design.

As I understand things, the DVs do snap shut on the delivery of fuel stopping, and thus influence the clean stopping of fuel through the injector nozzle (shock waves bouncing back and forth thru the injector and high pressure lines, etc). That flat cut into it allows slow equalization of pressures between the head-rotor and high pressure line. so as to help ensure correct starting of the next injection event.

Many of the DVs are designed to influence the opening and closing of the injectors so as to help ensure a clean injection event. One could liken what's going on to "water-hammer" in water supply plumbing. You get water flowing, then suddenly slam the valve closed. That banging or "Water hammer" is a shock wave bouncing off the closed valve, etc. The same thing happens in our injectors (generally speaking). The various designed DVs help correct that and other related issues.

Clear as mud?

I actually have a set of DVs that sport that same exact plunger. I can't recall for sure just now, but I think that is also used in our truck's Cummins.

 

So its actually just an orifice for all pressure below injector pop pressure.. makes sence I just have never seen these before and ive had 4 different dodge/cummins VE's apart. do you think this was a Cummins, Bosch, or Bluebird design?