had to look at where y'all are from with your fuel mileage, Im from TX mostly flat and rolling hills, I do get about 22-25 MPG running empty, The 35ft gooseneck when loaded with hay will bring it down to around 18 if I keep it around 65 MPH. When I pull the camper, all fuel mileage bets are off. Its like dragging a parachute behind me.
Still have to laugh at the guys who swear ANYTHING but SCT will blow your transmission and kill the engine. Kinda reminds me of an old Beatles song "He cant be a man, cause he dont smoke the same cigarettes as me,"

 

How much pressure did the gauge show?

 

25mpg out of a 6.0? You better never sell that truck cause you've got the only one that will do that!

 

Damn sending unit is bad, got put on day shift at work and I haven't been able to call GlowShift before they close (lovely PST). I'll get to it soon, too much headache went into installing that thing!

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1. Not to give Mdub707 a big head, but don't sell a rig that turns those kinds of numbers.
2. The song in question is "Satisfaction" by The Rolling Stones.

 

One year and 10 months later I finally get around to getting things squared away. Here's the numbers everyone was wanting with the Gillette spring:
Idle: about 95 psi
WFO on SRL tune: about 60psi

Conclusions:
1. The GlowShift gauge probably worked all along, that spring was pegging it out. Had I known that the spring was such a high psi piece, I probably would have left that gauge in.
2. Dropping 30~35 psi with my foot in Matt's SRL tune makes me glad that I don't have a blue spring.
3. It's been almost two years, and I don't baby my truck, if all of the horror stories of shreading o-rings and stuff were true, I would have done it already.

 

Well as long as the blue spring holds more than 60psi, you shouldn't be going below that no matter what spring is in there... it's a volume thing. You're not always going to drop 30psi no matter what. If it holds WOT at 60psi, it should do it with either spring in there bud. You're just over-stressing the pump at idle by trying to make 80+psi with it...

 

Because it's a return pump, I don't know how much stress it is really putting on it. I was talking to one of my power plants guys and this came up (helos and diesels have very similar fuel systems). Now if it were a dead head, like the Holley Blue in my Hot Rod, the extra psi would probably blow it up.

Bottomline, I have a blue spring on the way, if it keeps it above 60psi WFO, I'll leave it in. I'll keep y'all posted when I make the change. I won't take two years this time.

 

haha, interested to see how you make out with the blue spring. In theory... it shouldn't drop more than the lowest reading you had on the gillette spring... We know that spring will hold 95psi right? Meaning it wont pop off and bleed pressure less than that. This tells us the lower pressure at WOT is just from the injectors draining pressure, the spring is no longer even in the equation at this point. So as long as whatever spring is in there can hold higher than 60psi, it should never fall lower than where you were with the gillette unit. Make sense? It does in my head, but sometimes translating that to words is harder.

And of course we all know, theory doesn't always = real life.

 

Blue spring in, holds about 65~70 psi, doing a short run to Speedco for coolant/information, we'll see what the WOT psi is. Sinister coolant by-pass also in.

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Kinda like the blue spring, kinda don't. I like that it doesn't fluxuate as much pressure, but I don't like seeing 55 psi with my foot in it. I read that the Gillette spring can be "tuned", as in trim a coil, drop 10 psi at idle. By that math, 2.5 would be 25 psi taking it down to 70ish cruise psi.

 

You'll get to a point clipping coils where the spring is no longer even in contact. Translating a PSI drop by clipping X amount of coils is a very general rule of thumb, if you do want to clip it, be careful, start small and work up.

Why is dropping to 55psi a bad thing? That's right where Ford wanted it anyways...

Which fuel filters do you use? New style with the lip and the o-ring on the frame mounted one, or the old one's?

There is no need for 70+PSI of fuel pressure IMO. 55-60 is ideal. Have you given any though to reading behind the heads at all?