Dieseldummy:

Yes you are right. The higher volumes and pressures of the 4 piston pump do assure a better spray pattern but at what cost? The DB2 already sucks up close to 3 HP with 2 pistons. What the extra pistons would add I can only guess.

The point I'm trying to make is that the boys at GM did a pretty good job of sizing the pump to the engine in order to do the job they intended. Stanadyne states that the DB2 is available in sizes up to 25HP per cylinder (4911???). Though I doubt the head design is capable of 200 HP, it does look like Dr. Lee has come real close without a turbo. This means that the engine, if made properly can flow enough air to accept this amount of fuel without an added push.

Now back to the topic. Assuming your trucks require 25 to 30 HP to maintain 60MPH (just guessing at the numbers here) then using the formula of .43 lbs. of fuel per shaft HP per hour, then this engine will require 12.9 lbs of fuel to travel 60 miles. Based on 6.5 lbs/gallon, that gives us 1.98 gal per hour or about 30 miles to the gallon (sound familiar?)

That also means the pump (regardless of chamber size or the number of pistons) is only pumping out a fraction of it's capabilities to maintain this power level. If the pump and injectors are sized and matched I can't see a significant gain in bumping up the fuel delivery.

Just my thoughts

Bill