Pump Balancing... Pandora's Box?

Ok, I'm a wrencher, period. Short of equipment and know-how, I'm the type of person that would much rather do the work myself. But... there comes a point in life where you simply don't have the equipment or know-how to do it.

I've tweaked my own pump and have really enjoyed the benefits of knowing what does what, understanding the governor, rack travel, afc, etc. I've got a 4GSK in it as of now, which I feel is working and functioning within it's normal specs. I can leave the line at 4,000 if I want, but the most she'll turn once the load is on is 3,600 rpms. I've setup my truck to be a DHRA Street Diesel class vehicle and obviously want to take full advantage of the rpm limit set forth in this little rule:

The engine must be governed to a maximum of 4500 RPM, measured in the unloaded, free-rev state. The burden of proof of legal RPM lies with the puller. The use of a verification method, such as electronic recall tachometer, data logger or laser tachometer, is strongly recommended. A puller who cannot provide such evidence upon request will forfeit winnings and is subject to proof of RPM compliance before being allowed to participate in future sled pulls.

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Now, I don't know much about the 5GSK, but as the letter of the rule, one would assume the 4500 rpm free-rev state rule would fail on a 5GSK if it exhibits the same behavior as my 4GSK. Right? But my 4GSK seems to come up a little short, I need like a 4.5GSK. So....

I hear about people sending their pumps off to be balanced, governors lightened and the secret squirrel settings regarding fueling changed. So what exactly happens? The balancing part, I can sort of see, I assume we put it on a bench, measure the fuel from each P&B, then what? Spin the barrel a tooth to adjust how much fuel each one gets till they're the same? Or is there more to it?

The rest I do not understand at all... :bang

Lighten the governor? What? Grind some off of it? Remove parts of it? What EXACTLY is this?

And finally, adjustments to the fueling vs. RPM. I have read and heard people say I had [insert pump doctor's name here] adjust my pump to fuel to 4,xxx rpms. Huh? How? There's a 4GSK and a 5GSK, so how do you "adjust" this? Are there other secret springs capable of such fine spring rates that you can adjust a pump to a infinite number of rpms?

Bottom line: I want to have my truck go down the track and provide full fuel down the track at an RPM closer to 4,000 than I am now (and still pass that pesky rule I quoted above), but I want to understand how that's done prior to me sending my pump off to the closest pump witch doctor.

Any help would be greatly appreciated. Thanks!

Still doenst explain what he's looking for. I think he knows that already...

wildmanben said:

Still doenst explain what he's looking for. I think he knows that already...

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Correct. Although after thinking a little bit more about it, I may have worked it out myself. Does lightening the governor assembly involve removing counterweights, thereby requiring more centrifugal force to compress the governor springs resulting in more Rs?

So nobody wants to say out in the "open", ok... I'll continue my research and find out on my own. Thanks!

I think he's asking what kind of spring modifications.

Most spring kits with stock weights reach full rack 300 to 500 rpm below no load rpm. If you search you can find some that will full rack 150 rpm give or take below no load and be set to pretty much whatever rpm you want. I've read the DHRA rule but I thought they weren't enforcing it. I was told they only recalled after a run to see if you went over 4500 but didn't check free rev rpm. Does anyone know for sure?

CPMac said:

Most spring kits with stock weights reach full rack 300 to 500 rpm below no load rpm. If you search you can find some that will full rack 150 rpm give or take below no load and be set to pretty much whatever rpm you want. I've read the DHRA rule but I thought they weren't enforcing it. I was told they only recalled after a run to see if you went over 4500 but didn't check free rev rpm. Does anyone know for sure?

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Locally in my neck of the woods they are sort off goofy on this rule. Now, in my head if some tech guy wants to sit and my truck, stomp it to the floor and see how far she revs.... oke: well, I'm not exactly warm and fuzzy about it and neither have been the other associations that I've pulled with. What I've seen is more of a hybrid, like you said, they allow "up to" 4500 rpms running down the track, which implies that you could free rev close to 5000. Or, if enough people don't like the tone of the exhaust compared to others going down the track and we don't have a tach pick-up on the sled, then more questions are asked. But, to date, I have yet to see anyone use a laser tach or similar to validate this rule.

That said, I still want to run within these guidelines for the day when tach pick-ups are used or this rule becomes enforced to the letter (which it should if it's written in the rule book) :rules:

CPMac said:

I've read the DHRA rule but I thought they weren't enforcing it. I was told they only recalled after a run to see if you went over 4500 but didn't check free rev rpm. Does anyone know for sure?

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Was talking to Garrett Shields about this and he said that the tech guys will pick a few random people in the class and check their recall tach to see of they went over. If you cant prove it somehow, your busted...

Satburn,
You finding anything out about this? My mind is curious as yours on this...

wildmanben said:

Satburn,
You finding anything out about this? My mind is curious as yours on this...

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Sort of... I still have more questions. PM sent.

Id like to know more about the flyweights in the pump vs. rack travel also...........

Lance