OK, I've got a '85 Crew Cab with a full '92 Cummins swap in it and only 68k miles. It is a 4x4, with the stock automatic and 3.54 gears. What I've done so far is a 16cm exhaust housing, full 4" Stans headers exhaust (including downpipe), AFE air cleaner, and turned the full power screw about 1 1/4 turns.

Well my buddy recently bought a bone stock '92 D250 Club cab, 2WD, with the Cummins of course. We twisted his full power screw what we believe to be about the same - 1 1/4 turns, and that thing runs like a raped ape now!! We lined them up for grins and he walked away from me, to the tune of at least 3 truck lengths! WTH?! One thing I noticed right off is his truck smokes a moderate amount more than mine (mine really hardly smokes at all). His lets out a real good puff on startup, and under WOT it smokes more than mine. It's like his full power screw mod did more to his pump than mine? Is that common?

One question I have regarding turning the fuel power screw....do you turn it until it gets "hard" to turn? Obviously its not that easy to get a screwdriver in there where it makes solid contact and you can really put force on twisting it. I'm thinking I could go further on mine but should I try? Or should I move on to other mods?

How much quicker should his truck be considering the weight advantage he has? I've got the added weight of the crew cab and 4-wheel drive. Could that alone be why he pulled away from me like that?

Anyway - here is what I would like to do.....get the 'Ol Smokey fuel pin, 3200rpm spring, and twist the AFC star wheel a little. (On second thought, do I need to adjust the star wheel since I'm doing the fuel pin mod??)

If thats not enough to get him I'll spring for some injectors but at that point I'm sure I will have already surpassed the limitations of the stock tranny. That will need to be upgraded next.

What do you guys recommend? I'm just getting my feet wet with diesel performance but I can't let him get away with this!!

 

i want to see pics of this truck

 

The cheapest thing is sneak over at night, put 2,000 pounds of sand in his bed, and then race again. All that extra weight and friction hurts the ol' drag racing. Even it up!

 

They all react a little differently to pump adjustments.

Don't force the power screw, you will break it.

He's probably got close to 1,000 lbs less weight and that will make a huge difference.

Read up on pump adjustments, it sounds to me like you could stand to loosen up the star wheel. Also make sure the AFC cone is set to the deep side.

 

No two pumps are the same. He's obviously pushing more fuel than you according to the smoke. What tranny does your buddy have?

 

His has the automatic tranny as well.

 

Well I have been reading through the sticky's and links on VE pump adjustment...but the link I read just had step by step instructions if you were doing the mods one at a time. Since I'm going to go with a 'Ol Smokey fuel pin, do I still need to do the star wheel adjustment?

What do you think about injectors?

Thanks!

 

Hes got you with the wieght. You have more mass to get moving. Your going to have to match his power and then some.

 

The starwheel adjustment is really to personal taste, so it's not a matter of NEED as much as it is setting the pump up for your driving style. Once you get the pin installed, you're gonna want to do a series of WOT test pulls from zero boost and record how the truck reacts as far as smoke, spoolup and overall power. I would start with the starwheel as far to the top (CCW) as it will go without binding the spring and then run it down (CW) 2 full turns after every run. As you run the starwheel further down, less boost is required to get the fuel pin (old smokey or stocker) moving down the bore. This will equate to more fuel for a given amount of boost and, depending on your full fuel screw settings, can lead to some pretty thick smoke. After toying around with these pumps a fair bit, I can safely say that more bottom end fuel is not always better for spool or power. There's a line there and there's also a compromise that's individual to each driver that simply can't be put in a+b=c format. Some dudes like to roll the coal no matter what while others want a sparkly clean exhaust from a standstill on up to the governor. Peak performance does not equal peak efficiency, either...if it did, pulling tractors would not bellow soot 60 feet into the air Test and tune with what you've got--it's pretty amazing how many different attitudes the same truck can have and you might be surprised what affect a fine-tuned AFC can have on even stock injectors