LOGANSTANFORTH
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Cat 3116
To gain access to the fuel screw on the 3116, you must remove the valve cover. If the seal tag/plate is still present it will need to be removed. You will need to remove the tag by removing the rocker shaft stand bolt. The screw and lock nut are on the rack bar. Turn the screw counter-clockwise to increase rack travel. One source says you'll need some special tool to do it, I have yet to verify. Marine injectors are also available for an even better power increase.
Cat 3208 & early model 3306
Tools needed-7/16" socket, a short extension or 2, and a screwdriver. If you look on the top of the pump you'll see a cover with 2 bolts that's about the same size as a Holley carb's float bowl. Fuel does come out sometimes, and does not need bleeding afterwards. Under it is a screw with a jamb nut. If you hit the accel. linkage you'll see a little pin come up. The screw stops the pin and thus, limits fuel. So adjust it as far up as you can as long as you can tolerate the black smoke. Most turbo'd 3208's can run fine with the screw all the way out(removed). And just behind that is the high rpm governor adjustment. It's labeled as 'high idle', but only go 2-3 turns at a time as to keep it under 3200 no load. Backing the screw out raises the rpm. One more adjustment is the pre-boost power. This is up in the front of the other 2 adjustments. It's round & has 3 bolts holding it & 6 holes in it. Take all 3 bolts out and you may have to smack it with something to break it loose(mosly from paint). Now tighten it like you're screwing it in tighter, that makes the power come in sooner. If you go 'til it stops, then you may see lots of smoke if you mash down on the pedal. Back it out as needed.
Cat 3126
10k powerstroke mod works, but use a 4.7k resistor instead. Results aren't that great though, if you have an auto trans. Most notable power increase is around 12-1800 rpm, after that it's hardly noticeable. ICP sensor is up next to the valve cover, just a little ways back from the front on the driver's side. You can also put a 3.9k resistor on the manifold pressure sensor(MAP sensor in the gasser world). It uses the 5 volt source to sensor return, not ground. Other than that, Edge makes a plug in module for them.
Cat 3406A,B,C , and later model 3306
On the back of the pump is a cover/plate that is said to be almost heart shaped(the AFC housing). There are 2 allen head screws behind that plate that have 3/8 (on B&C's pumps, a single 7/16 on the A) locknuts on them. On an 'A' model you can just take the screw out, since it cant flow enough to cause any harm. Carefully loosen the locknuts with a deep socket, then remove ratchet and insert the allen wrench through the socket so you can hold the locknut in one place. Turn both screws EXACTLY the same amount of turns. Usually start by going 1 full turn on both, then run it. Any additional turns afterwards should be no more than half. Don't get greedy, you'll burn it up. You can get well over 500Hp playing with those B model pumps, but don't come back here blaming me if you don't know how to take your foot out of it and let it cool down. With the screws were turned all the way out, and a C model turbo on it, you can get a little over 600Hp. But it gets hot, if not careful.
Cummins Big Cam
drill out the ball in the throttle shaft and back out the screw a bit
adjust your aneroid valve so it gets rid of the fuel supply delay to make it more responsive ( the aneroid's function is to limit fuel until the turbo spools up. Its behind the little tin cover beside the throttle shaft).
shim the governor spring
change the fuel pump button (I think its actually called an 'idle plunger' or something). This is the biggest bang for your buck. Its not that hard to do but I can't recall the specifics because its been over a decade since I did this. A few hand tools are all thats required to pop the cap off the end of the pump then a socket and needle nose pliers to pull the stuff out. The 'buttons' are stamped with a number on the groove where it is narrower and the lower the number, the more fuel pressure. The numbers go up in a weird sequence if I can recall --> alternating between the increase of 2, then 3, then repeat --> like 5, 7, 10, 12, 15, etc. Depending on how far you want to go, guys used to take whatever they had and drop the number by 10 or 15 and it was pretty safe. Just be sure to have a pyro (that works properly), be sure to warm it up properly because that extra fuel will score a liner much quicker when not warmed. Do not lug the engine - drop a gear soon as there is enough rpm room to do so. Someone had an '84 Big Cam III and it had something like a 30ish button and we ran a 5. It was 'hot'!
The fuel pressure increased from somewhere around 180 to over 300. Some guys had a hard time with turbos when they did this.
Detroit 8.2 liter
Tools needed-screwdriver and I think it's a 9/16" wrench. On top-middle of the pump on the right side there's an all-thread looking screw with a jamb nut. Loosen the jamb nut and take the screw out. There's a spring inside it, so be cautious. Run the jamb nut so there's about 4-5 threads left and re-install the screw. Run it up to the jamb nut, then tighten the nut up and it's done. Not much, but it's free.
Detroit V92's
Detroit 6&8V92:
Adjust the no load speed up.
Back out the buffer screw a few turns.
On the back side of the governor is the cap held in by 2 bolts, take that off and you have access to the idle control and the top no load setting.
Loosen the small 1/4" nut at the end pack and back out the idle speed screw about 4 turns. Loosen the large clamp nut with the 4 notches in it on the other end of the pack. then screw in the entire assembly 3-5 turns. Tighten the large clamp nut. Fire engine up and adjust the idle screw to just below the desired idle. Tighten the idle screw nut.
Adjust buffer screw to desired idle and so when you stab the throttle the gov doesn't search. Put cap back on and run it around and adjust from there.
You can also get better response by running a tight rack but with you sand jockeys playing with that makes for a good runaway so just jack up your no load adjustment and try to keep it below 2600 rpms at top no load.
To gain access to the fuel screw on the 3116, you must remove the valve cover. If the seal tag/plate is still present it will need to be removed. You will need to remove the tag by removing the rocker shaft stand bolt. The screw and lock nut are on the rack bar. Turn the screw counter-clockwise to increase rack travel. One source says you'll need some special tool to do it, I have yet to verify. Marine injectors are also available for an even better power increase.
Cat 3208 & early model 3306
Tools needed-7/16" socket, a short extension or 2, and a screwdriver. If you look on the top of the pump you'll see a cover with 2 bolts that's about the same size as a Holley carb's float bowl. Fuel does come out sometimes, and does not need bleeding afterwards. Under it is a screw with a jamb nut. If you hit the accel. linkage you'll see a little pin come up. The screw stops the pin and thus, limits fuel. So adjust it as far up as you can as long as you can tolerate the black smoke. Most turbo'd 3208's can run fine with the screw all the way out(removed). And just behind that is the high rpm governor adjustment. It's labeled as 'high idle', but only go 2-3 turns at a time as to keep it under 3200 no load. Backing the screw out raises the rpm. One more adjustment is the pre-boost power. This is up in the front of the other 2 adjustments. It's round & has 3 bolts holding it & 6 holes in it. Take all 3 bolts out and you may have to smack it with something to break it loose(mosly from paint). Now tighten it like you're screwing it in tighter, that makes the power come in sooner. If you go 'til it stops, then you may see lots of smoke if you mash down on the pedal. Back it out as needed.
Cat 3126
10k powerstroke mod works, but use a 4.7k resistor instead. Results aren't that great though, if you have an auto trans. Most notable power increase is around 12-1800 rpm, after that it's hardly noticeable. ICP sensor is up next to the valve cover, just a little ways back from the front on the driver's side. You can also put a 3.9k resistor on the manifold pressure sensor(MAP sensor in the gasser world). It uses the 5 volt source to sensor return, not ground. Other than that, Edge makes a plug in module for them.
Cat 3406A,B,C , and later model 3306
On the back of the pump is a cover/plate that is said to be almost heart shaped(the AFC housing). There are 2 allen head screws behind that plate that have 3/8 (on B&C's pumps, a single 7/16 on the A) locknuts on them. On an 'A' model you can just take the screw out, since it cant flow enough to cause any harm. Carefully loosen the locknuts with a deep socket, then remove ratchet and insert the allen wrench through the socket so you can hold the locknut in one place. Turn both screws EXACTLY the same amount of turns. Usually start by going 1 full turn on both, then run it. Any additional turns afterwards should be no more than half. Don't get greedy, you'll burn it up. You can get well over 500Hp playing with those B model pumps, but don't come back here blaming me if you don't know how to take your foot out of it and let it cool down. With the screws were turned all the way out, and a C model turbo on it, you can get a little over 600Hp. But it gets hot, if not careful.
Cummins Big Cam
drill out the ball in the throttle shaft and back out the screw a bit
adjust your aneroid valve so it gets rid of the fuel supply delay to make it more responsive ( the aneroid's function is to limit fuel until the turbo spools up. Its behind the little tin cover beside the throttle shaft).
shim the governor spring
change the fuel pump button (I think its actually called an 'idle plunger' or something). This is the biggest bang for your buck. Its not that hard to do but I can't recall the specifics because its been over a decade since I did this. A few hand tools are all thats required to pop the cap off the end of the pump then a socket and needle nose pliers to pull the stuff out. The 'buttons' are stamped with a number on the groove where it is narrower and the lower the number, the more fuel pressure. The numbers go up in a weird sequence if I can recall --> alternating between the increase of 2, then 3, then repeat --> like 5, 7, 10, 12, 15, etc. Depending on how far you want to go, guys used to take whatever they had and drop the number by 10 or 15 and it was pretty safe. Just be sure to have a pyro (that works properly), be sure to warm it up properly because that extra fuel will score a liner much quicker when not warmed. Do not lug the engine - drop a gear soon as there is enough rpm room to do so. Someone had an '84 Big Cam III and it had something like a 30ish button and we ran a 5. It was 'hot'!
The fuel pressure increased from somewhere around 180 to over 300. Some guys had a hard time with turbos when they did this.
Detroit 8.2 liter
Tools needed-screwdriver and I think it's a 9/16" wrench. On top-middle of the pump on the right side there's an all-thread looking screw with a jamb nut. Loosen the jamb nut and take the screw out. There's a spring inside it, so be cautious. Run the jamb nut so there's about 4-5 threads left and re-install the screw. Run it up to the jamb nut, then tighten the nut up and it's done. Not much, but it's free.
Detroit V92's
Detroit 6&8V92:
Adjust the no load speed up.
Back out the buffer screw a few turns.
On the back side of the governor is the cap held in by 2 bolts, take that off and you have access to the idle control and the top no load setting.
Loosen the small 1/4" nut at the end pack and back out the idle speed screw about 4 turns. Loosen the large clamp nut with the 4 notches in it on the other end of the pack. then screw in the entire assembly 3-5 turns. Tighten the large clamp nut. Fire engine up and adjust the idle screw to just below the desired idle. Tighten the idle screw nut.
Adjust buffer screw to desired idle and so when you stab the throttle the gov doesn't search. Put cap back on and run it around and adjust from there.
You can also get better response by running a tight rack but with you sand jockeys playing with that makes for a good runaway so just jack up your no load adjustment and try to keep it below 2600 rpms at top no load.