I bought a '94 pump from a 3500 automatic. I have a guy who is going to step up a P7100 pump in a big way for me. He says this pump, the 94, is not as good as a 97 or early 98 for radical upgrades. I thought P7100's are P7100's. Anyone know which ones are better for serious tweaking?? How can I tell the difference?

 

the best stock pumps are from a 96 to 98 12v 5 speed truck[215hp] pump #S 887 and 913. followed by the 96 to 98 auto trucks[180hp]

 

Gunracer is right on what the best stock pumps are, But if you are going to extensively moddify it to make it like a race pump any one would do, because you pretty much rework everything. The PDR stupid pump that I have originated from a 160Hp pump, because they can be had chepely.

 

One thing that people tend to overlook is that the 913 pump has variable timing. This helps with fuel economy (at least a little) and throttle response (definitely a lot) if it is properly tuned with regard to the afc. The 913 runs about 4° more advanced at about 1/4 throttle or less and then goes back to regular timing after that. I like it mostly because it helps get the truck off the line faster and makes the truck more drivable with an auto. ALL OTHER p-7100 PUMPS including the stupid pump have completely fixed timing.

 

I didn't know that. What engines did this 913 pump come on? Is there a marking on the pump to identify it?. Thanks.

 

The guy who is doing the pump is going to max it out, so to speak. He says he likes to start with the 96-98.5 pumps. Thanks for the information. He said not to get rid of the '94 pump. It is still a good core.

 

Extreme diesel..i don't know what your talking about ..all P7100 pumps are timed and set with a gear and locknut, there's no way it can change during operation..there's no such thing as "variable timing" on these,sorry..maybe a vp-44.

 

Yeah - 'splain me dat, lucy!

1 - where's this mythical nomenclature tag located on the P7100 pump (not the one on the timing case) where the xxxxx913 number might be seen?

2- the xxxxx913 has variable timing? Varied by the governor weights?

 

The "913" in question is the final part of the serial number which is located on the label on the side of the pump. It is covered by the plate which holds the bellcrank for the throttle linkage. If the timing is variable, I'm sure it can be seen with a pulse adapter and timing light, while increasing RPM. I never really tried it before.

 

Thanks - the engine data plate on the timing case was previously removed, for who knows what nefarious reason(s).

 

the timing advance he is talking about if from the helix cut on the plungers. now how much advance i do not know.

 

To each their own don't follow everyone else to the "T" though. got...DIESEL? is running twins on a 160 pump with a 100 plate (yours truly), 370's, and 191's and let me say the thing is INSANE! Alot of folks said you can't fuel twins on a 160 pump, WRONG! They have the ability to dish out more than most think! His manages to deliver BIG fuel for his BHT3B/HX35 twins! Don't get me wrong if you've got a chance to get a big pump go for it but just let it be known you CAN do big fuel on a 160 pump. I guess it all just boils down to how much horse do you want and how much growin room do you want left for ya. In got...DIESEL's case he was doing budget twinsso he took a chance and it worked out just fine. Could only imagine what his truck would do with DonM's injectors in it!

 

There was an excellent, lengthy thread several years ago discussion the timing advance/retard of the 913 pump. On the 913 compared to the 160/180 pumps are the tops of the plungers different. On the 160 and 180 pumps the top of the plunger is flat. On the 913 there is a "valley" in the middle and "peaks" on each side. When the barrel rotates depending upon rack travel the spill port will be covered earlier by the peaks but will stay open longer when exposed to the valley. The spill port determines when the fueling begins and ends. So with a flat topped plunger this never varies - hence no change in timing, but the helix cut in the side of the plunger determines the amount of fueling. With the 913 pump it is slightly variable - hence a change in timing. Hard to explain in words but with pictures it's even muddier.

 

Yeah... what he said. I never knew about this until I took one apart. Once you have the delivery valves out, you can easily see how it works if you already know how an injection pump works. The rotary pumps can vary timing with rpm. This pump does not. The timing changes with rack position and it's advanced at part throttle and retarted at full throttle. I just got a complete 215 engine and I'm throwing it in my truck after it gets an overhaul. I think the variable timing makes the truck nicer to drive in the city.

 

Ok, lemme get this straight: I have a '98 5 spd, which of course has a 215 pump. Nothing internal has been done to the pump, other than removing the afc arm, advancing the timing through the normal means, and replacing the fuel plate. Does my pump have variable timing?