Governor Washer/Shim Mod
The governor on Bosch 'P'-pumps is 2 heavy flyweights that push against a set of springs(1 per flyweight). The stiffer the spring, the higher the rpm will go before it starts to defuel. You could also tighten up stock springs without adding these washers or new springs. Tightening the springs are about 100 rpm per "click" of the gov. nut(explained later in this article), with a max of 4 clicks.
You have two choices when it comes to accessing your governor springs. One method is to remove the AFC housing, remove the fuel plate and go through the top of the pump. This method is more comfortable for many people because they have most likely already replaced or adjusted their plate and this is familiar territory. The drawback to this method is you cannot remove or replace your idle spring (the big one on the outside) and you have to do everything with a magnet and there is a large risk of dropping springs/washers into the bottom of the pump (which I’ve done).
The other method, and my recommendation, of accessing your governor springs is through the access hole on the side of the pump. This method requires loosening the shutoff solenoid and removing the shutoff solenoid linkage, so it may take a little longer but this is my preferred method of removing the springs for the following reasons. First off there is zero chance of dropping a spring into the bottom of the pump. Also the springs, the stud and the nut are all right there for easy access with your fingers. Finally, it is much easier to measure the stud protrusion to ensure that you have both sets of springs adjusted to the same preload.
I'll start off with some pictures to help give you a general idea of where to look. Forgive the terrible picture.
Once you remove the shutoff solenoid linkage (be careful not to drop the half-moon keyway), and remove the plug (uses a 7/8” socket) you will need to rotate the engine over until you see the springs in the picture below. Easiest way is to use a 7/8” socket on the alternator and rotate in reverse. It’s only going to turn one direction, and wont cause any bearing damage since you will only be making a little over 1 rev in reverse.
Before you begin removing anything, it's always a good idea to measure the stud protrusion before you take anything apart(pic 2 & 3). That way if there is ever a problem you can always put it back like it was. I use a set of calipers to measure the stud protrusion. We are just trying to find out how much of the stud is sticking out past the top of the nut.
I use the bottom of the calipers to take this measurement. Open the calipers and place the tip of the extension on the top of the nut as shown.
Now slowly close the calipers until the base hits the stud. As shown here in the second pic.
This measurement will vary depending on how straight you are able to keep the calipers and how much you shake. Try to keep them at a 90 degree angle to the face of the nut. Repeat this procedure several times until you can get the same measurement repeatedly. On a stock truck the measurement should be somewhere around .050" although it does vary a bit from truck to truck.
Now you can remove the nut and the top seat of the spring pack as shown below.
You will find three springs inside all stacked inside of one another. Each washer goes on one stack of springs, and you'll get to the other set of springs in a little bit. They will look similar to the ones below in pic #1. Lower spring seat is on left.
No springs are removed for the washer/shim mod. The washer should in NO way come in contact with the outer spring. That’s why it’s important to use a 3/8” washer, and then drill out the middle to ½” (13mm). The ½” washer is too big in diameter, and will bind up the idle spring, and cause it to idle at about 12-1500 rpm. I did this as an experiment on a truck and to take some pictures. If you look at the photo below of the washer, you’ll see how close it is to the outside edge. This is a ½” washer for reference in pic # 4, and is what you need to look for. Make sure your washers are 18mm OD, 13mm ID, 1.55mm thickness. This is a little more technical than just doing a GSK, but this can get you 3000-3200rpm (give or take a few hundred rpm) for the cost of the 2 washers. Another note; some injector pumps dont work well with this mod, and they will idle at 1500rpm. I haven't got info on which exact pumps do this yet.
The largest spring is the idle spring. You will need to REUSE this spring when doing a 3,000 or 4,000 rpm spring kit. (For reference: When installing a 3,000 rpm kit, you will replace the two small springs with two slightly stronger springs and a new lower spring seat. When installing a 4,000 rpm kit, you will replace the two small springs with the 3 springs and lower spring seat provided.)
Installation is simply the reverse of removal. Install the washer over the top of the 2 smaller springs, and then install the spring retainer and the nut. You will get a tighter preload than original, so don’t just count “clicks”. Also, notate the orientation of the nut, like the slot is at 1 and 7 o’ clock. Once you get that together, you’ll need to rotate the engine 1 revolution to get access to the other set of springs. Then do the same washer installation, and preload on the nut, and that’s it.
Preload on the nut is CRUCIAL to a smooth running engine. I've found that .030" - .040" stud protrusion is best for the automatic equipped trucks. This is LESS nut tension than stock. There is a transition range when the flyweights are only being held in by the idle spring to when the entire pack of springs is pressing against them. During this transition phase the engine will run slightly rough. By adjusting the amount of stud protrusion, you can adjust at what rpm range this rough running occurs at. By reducing the tension, it lowers the rpm range of the stumble. If you place the stumble range BELOW the stall speed of the converter it is not noticed and the truck runs smooth. You can do the single “click” adjustments from the top, through the fuel plate access hole, it’s much faster.
When re-installing the shutoff lever, make absolutely sure the keyway doesn’t slip to the back side & fall out. It’s really small & easy to drop, as I found out. Don’t be scared to do it, just be aware. Then it’s just putting it all back together, and going for a test drive.
I hope this has helped you understand the governor washer mod a little better. Thanks to Relentless Diesel for some of the pictures and part of the text, and Gunracer1 for initially posting about it.:bow:
my daily driver:67 F100, 300 4V, cammed, 4 spd.
or, 08 Subaloser Forester, 2" lift.
work rigs: 94 IH 4900, DT466(originally 230hp), #0 fuel plate, tighter gov springs, 22* timing
or, 06 IH 7400, DT466E, 300hp
My Low Buck fuel rate site:
Last edited by nevrenufhp; 01-07-2009 at 12:36 AM.