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Pump Tuning - Part 1

By
booneylander
840

With the head gasket having blown and needing to be replaced I launched into a whole array of upgrades for the truck as it was going to be out of commission for a while and these trucks seem to be a good platform for upgrading, apparently responding very well to inexpensive mods and tuning.

In this two part chapter we'll be launching into the following :

-3800 rpm governor spring install

-M&H Number 3 Fuel Pin Install

-Longer AFC follower pin

-Uprated AFC Spring

-M&H Dynamic Timing Advance Kit

-Pump Timing Adjustment

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One through Three. Here are a few shots of the pump, in case you weren't sure where to find it. I've taken the liberty of identifying it with an arrow for clarity.

Four. This here is your AFC cap. Go ahead and pull the four screws out of the head. Chances are they've been seated in place there longer than some of my ex girlfriends have been alive so go easy on them, they might put up a struggle, but be patient and gentle and they'll give it up for you.

Five and Six.. With the cover off, you can see the top of your AFC diaphragm. It may be covered in iron dust coming in the boost pipe from the head. Don't worry about it. But do put a mark on the top of the hat and at the front of the housing. If you're re-using the stock fuel pin you'll want to have the pin aligned the same so this can be important.

Seven. Here you can see the stock fuel pin with the witness line where the AFC metering pin had been riding on it.

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One. Now that you have the top and diaphragm off, you can pull out your AFC spring here and set it aside so you don't lose it.

Two. Time to unscrew this allen key that holds the top throttle linkage on and remove the whole assembly.

Three. Have a look at your alignment marks here and make a note of which markes your screw slot is aligned with. This will be important for putting everything back together properly.

Four. To keep removing throttle linkages, you'll need to remove this fuel line.

Five. Now take off the return spring assembly and it's washers.

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One and Two. Now mark your idle adjustment stopper screw and your max throttle stopper screw so you can return them to this position. In my case I will probably need to adjust them later on but at least I can set them back to this position as a baseline.

Three and Four. Feed the aforementioned screws into the housing so the housing bolts will clear them. I've identified the screws you will be removing in the next step.

Five. Unscrew the bolts. The cover will now be free. Oh wait just kidding, you need to pull the line off the back of the AFC housing there on the left. Now the cover will be free. Don't lose your crush washers!

Six. You can feed the throttle shaft through the cover. You may need the gentle touch of a heavy object to encourage it to come out.

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One. With the cover off you can see how the throttle linkage is arranged. The spring with the pink "386" identifies the spring in use. This one is the stock governor spring which limits the engine to an eye-watering peak speed of 2800 rpm.

Two. Here you can see I've placed a short section of wire in place of the spring just to keep the thumb-tab spring loaded thinger doodle (technical term) in place.

Three. Here is the stock spring (bottom) compared to the new spring I'll be using (top). The "374" spring will theoretically allow me to reach the stratospheric engine speed of 3800 rpm. It's important to note here that I'll be using stronger 60 lb valve springs to keep the valves from floating away at this tremendous velocity. I can hear you laughing, but if I were to throw one of the intake valves at your head you'd quickly understand why this is possible, as a single valve is larger and weighs more than an entire piston and rod out of your Honda Civic.

Four. There are other springs that can be used in here, such as a "366" which would limit revs to 3200rpm, this spring drops in unmodified with no issues. However my "374" (3800rpm) or the "354" (4200rpm) springs are longer than stock and require you to trim them to stock length or they will bind up in the housing and prevent you from ever getting the motor to idle or run properly. I think I pulled it off alright.

Five. Here you can see the modified spring installed.

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One. This next mod is a small but important change. Basically, when using some of the more aggressive fuel pins in the AFC, you can end up pulling the follower pin out of the housing, which allows fuel to leak out and basically cause you all kinds of problems, or the pin can snag and not go back in properly, etc. So you need to swap the follower pin out with a longer one. Here I'm removing the allen key cover plug to get access.

Two. Here's where the follower pin resides, but as you can see it is hidden behind this linkage.

Three. Check out these ball bearings, you'll need to find them on either side of the housing, then gently tap them out with a hammer or press them out so you can pull the shaft the linkage rides on out of the housing. Be extremely careful doing this, press one ball bearing into the housing until the opposite one pops out, DO NOT GO ANY FURTHER. Then flip the housing over and press/punch the shaft back the other way to drop the second ball bearing out. Once you have both out you can punch/press the shaft out either way.

Four. Here's the shaft on it's way out of the housing. It's a pretty tight fit.

Five. Here's the shaft and both ball bearings.

Six. Here's the linkage which should just drop right out with the shaft removed.

Seven. With the linkage out of the way you can reach in and pull the follower out with a small pair of pliers. If re-using the follower be very careful not to mar the surface. If the follower pin isn't easy to grab, have a look down the tube where the AFC fuel pin had been and you'll see the end of it, gently push it through with a screwdriver and you'll be able to grab it through the port.

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One, Two. Here are the follower pins. Stock is on the bottom and you can see the tip is a bit worn from decades of boosting. The top one, while it looks very similar, is actually 0.5mm longer and makes the difference between winning and failure. Apparently. Whatever. Swap it out.

Three. Feed that pin back in and then replace the linkage, throw your shaft in, which will probably require some tapping with a punch to feed it through, then replace your ball bearings in the housing to keep everything in check. Make sure the linkage moves freely.

Four. Replace the allen keyed cap.

Five. Now look at the back of the housing and mark the position of your max fuel screw. Back it out like so, and throw your throttle shaft back into the housing, set it on the base and make sure eveything is sitting properly, then re-install your cover screws.

Six. With the cover back on securely and your max fuel screw back in it's original position, feed your idle and max throttle stoppers back to their original position.

Stay tuned for PArt 2!

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Just parking some resources here for reference. Don't mind me.

http://www.4btswaps.com/forum/showthread.php?23841-4BT-6BT-injector-talk-pop-pressures-spray-angles-bowl-fill-timing-edge-filters

http://www.dieselbombers.com/5-9l-rotary-performance/15277-gov-spring-numbers.html

http://issuu.com/rswords/docs/boschvemanual

http://articles.mopar1973man.com/1st-generation-dodge-cummins/9-ve-injection-pump-tuning-up-a-ve-injection-pump

http://dodgeram.org/tech/dsl/morepower/Powerve.htm

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