ill try and describe what to do to the arm, the arm looks like the shape of a "L", and the afc arm when adjusted properly will ride on the bottom edge of the "L", now the is a shaft the the arm rides on, and goes straight through the arm, there are two ways to gain more rack travel, by either grinding off some material where the rack lever makes contact with the afc arm, or by grinding material off of the front of the barrel of the afc arm where the shaft rides through the arm. both gain rack travel, but there can be a downside to grinding too much material off of the face of the arm where it makes contact with the rack lever. if you take alot of material off there, you will loose the ability to control smoke down low with little no boost. now im not saying you can't remove material in that location, i removed maybe 1-1.5mm, and made it flat. if you notice most of the arms have a weird cut, or slant that is not perpindicular to the other edge. i did not like that, so i just made it flat, and 90* to the other edge. now at the barrel on the arm where the shaft goes through the arm, i removed about 2-3mm of material. after doing this, if you apply shop air, and let the arm extend all the way, you will notice that the barrel that you just ground down does not bottom out at the housing???? why is this? take a look at the washer on the shaft, the washer is bottomed out against the afc housing. if done right, you should have about 15.5mm of travel from all the way back to all the way forward. now the rack lever arm will travel about 5mm befor eit evne makes contact with the afc arm. now you do all of this, and reasemble the afc, after you have ground down the washers of course. notice how did not say just flip the washers, the one washer has a lip on it, and if you just flip it, that will give you more rack travel forward, but you then will loose the abililty to alow the afc arm to come all the way back to control smoke. by gringind the lip off of the washer, and smoothing out the edge so you dont cut the afc diaphram, you now have the ability to control your rack arm all the way through it's travel. the only 2 adjustments you will ever need to make on the pump is with the coarse smoke adjustment screw that is located on the back of the housing, and the starwheel that will control how much boost is needed to make the arm move out of the way, and allow rack travel. for the initial setting, back the coarse screw all the way out and then thread in untill it just touches the shaft that moves the afc arm. you may need to adjust this after driving the truck, it is possible to make the initial rack travel before boost allows the arm to travel further less than stock. this can really happen if you do not have the afc slid all the way forward. you will know if this happens because the truck will just be a dog down low, and them come alive in the mid to upper boost once the arm has moved out of the way. if you encounter this, all you need to do is loosen the jam nut, and thread the screw in about 2-3mm, or untill you feel that the truck has good power off the line, or in low boost. once you have that dialed in, it is just a matter of fine tuning the starwheel for spring pressure. that really the only adjustment you are going to need to make! it is that simple! there is no rocket science to this AFC modificaiton, and how to tune it. hope this helps! sorry i dont have any pics, ill see if i can get Weston to post up his pics.
Wes