Big Cam 400 - Dodge Cummins Diesel Forum
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post #1 of 6 (permalink) Old 10-14-2009, 07:26 PM Thread Starter
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Big Cam 400

Our fire department has a 1978 379 peterbilt water tanker. It holds about 4,300 gallons of water. She is a good old truck but the problem is she is a little slow. Our department serves a fairly mountainous area. I would like some tips on how to spice up this cummins a little bit. maybe some pump adjustments. It has a pyrometer and currently I can't get the egt's above 750-800 degrees so i know there is some wiggle room. engine is fairly fresh, was rebuilt about two years ago. time to turn her loose!


Black 2004.5,4x4,3500,SRW,QCLB Auto. AFE Stage II. Trans, Pyro, Boost in the cubby. Other Rigs:03 Jeep Grand Cherokee Overland, 76 Toyota Hi-lux, custom bed made from cherry bin, LED lights in rear, and it usually runs (as long as I hit the carburetor with a rock)
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post #2 of 6 (permalink) Old 10-14-2009, 08:39 PM
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Restrictor in the fuel return line will bump up the fuel pressure, throwing more fuel into the cylinders each time the injector fires.

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post #3 of 6 (permalink) Old 10-14-2009, 09:19 PM
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You might not have as much wiggle room as you think.
My bet is the pyro is post turbo, 950° would be the max safe egt.

BTW, I grew up inbetween Pateros and Chelan. Haven't been back in over 20 years.
Don't miss the winter fog at all.

Bill
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post #4 of 6 (permalink) Old 10-15-2009, 09:03 AM Thread Starter
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I will bet you are exactly correct on the pyro location. i will check today. thanks

Black 2004.5,4x4,3500,SRW,QCLB Auto. AFE Stage II. Trans, Pyro, Boost in the cubby. Other Rigs:03 Jeep Grand Cherokee Overland, 76 Toyota Hi-lux, custom bed made from cherry bin, LED lights in rear, and it usually runs (as long as I hit the carburetor with a rock)
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post #5 of 6 (permalink) Old 10-16-2009, 06:47 AM
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What fuel system is on the 400? Is it PT?

36 foot '93 Carpenter body on Spartan chassis. 5.9 Cummins with P-pump, intercooler, and waste-gated turbo. Allison MT643 tranny, and "huge" rear-end. 11R22.5 tires.
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post #6 of 6 (permalink) Old 10-18-2009, 08:03 PM
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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.

My low buck diesel fuel rate site: http://www.freewebs.com/nevrenufhp/index.htm
67 F100, 300, 4bbl...swapping in a 6.6(401)Ford dieselhttp://www.youtube.com/watch?v=zcflwjpRHUQ
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