mileage booster!! long trip to find out!

[dpuckett]

285s will drop your mileage slightly- 1mpg, I'd say. It's almost like having a dually (325s would be about equal to a stock dually in terms of rolling resistance).

What is your timing set to? I'd have expected 19-20 with your setup. Several guys I know who had the same truck as yours got 18-20, but that was back in "the day." Find true TDC, and start at 1.5mm and go from there. I'd suggest 2-3 tanks before changing anything. Also, where you get your fuel can make a difference. Locally, there is one chain that consistently gievs me 1mpg less than the others.

Valve adjustment, lift pump output, fuel filter, air filter, tire pressure. I've never noticed a lick of difference with the aerodynamic change with a bug guard. If anything, it'll reduce reisstance due to having fewer bugs on the windshield.

Might try your stock turbo back for S&Gs. You know, less mass to spool up?

DP

[Ace]

My fuel pin was wasting a noticeable amount of fuel until I tightened up the starwheel, backed out the smoke screw and cut down the inside of the AFC top enough to let the fuel pin ride all the way up. Those three things pretty well cleaned up most my low-bost smoke.

[apwatson50]

My fuel pin was wasting a noticeable amount of fuel until I tightened up the starwheel, backed out the smoke screw and cut down the inside of the AFC top enough to let the fuel pin ride all the way up. Those three things pretty well cleaned up most my low-bost smoke.

Dang, i've done all of these things on both my trucks and I still get a lot of no/low boost smoke. I have the star wheel almost up as far as it will go and still be on the catch.

I guess you're doing something right and i'm doing something wrong! I need to have you show me what i'm doing wrong!

[Ace]

Check the witness mark on the fuel pin to see if it's getting bottomed all the way out to the edge of the pin. It will be allowing early fuel until it does. I ground out the inside of that cover at least three or four times (a little at a time) until it got there.

[apwatson50]

Check the witness mark on the fuel pin to see if it's getting bottomed all the way out to the edge of the pin. It will be allowing early fuel until it does. I ground out the inside of that cover at least three or four times (a little at a time) until it got there.

It gets pretty darn close, I took the whole underside step out, so it is completely flat to where the threads are for the "smoke screw". Make sense? I don't think i'd want to take anymore out! I'll double check on the witness marks though.

I also took the stock pin and ground on the lower part of it, so there is no ridge, the pin could go to just about the bottom, if it can go up high enough. Need to double check that.

[apwatson50]

I'm thinking a spring with a higher spring rate would help also. All the springs I have are the green/blue one. There are different springs with different rates, should find a part number and try that.

[Ace]

I also took the stock pin and ground on the lower part of it, so there is no ridge, the pin could go to just about the bottom, if it can go up high enough.

That was also a part of what I did. I think the original BD pin was hanging on that bottom ridge.

My spring is red/green.

[apwatson50]

My spring is red/green.

actually that sounds like what I have also, pretty sure.

[SChandler]

Did you check your odometer? If you've recently changed to the 285's from the stock tires (say, around the same time as the IP work), then your odometer is reading slow because the 285's are about an inch taller than the factory 235's. Something to check for.

[Ace]

... if it can go up high enough.

That's also an important point. I don't know if it can. The inside of my top cover is ground just about all the way down now as well. To clarify what I did to the fuel cone - I tapped it with the MIG a few times in that ridge area to build it up a little. Then I smoothed it out so the profile runs right out to the edge of the pin at about the same level as where the ridge originally started.

I'm going to pull that fuel cone out again here one of these days real soon to see how it's doing since I repaired it. It seems to be running right again, I just hope it's wearing well since I welded and quenched it to try and improve the hardness. Back a few months ago I started noticing increasing levels of smoke and found the BD cone had given in to a pretty deep gouge from the guide pin.

[T.winegar]

ok. that might be the problem!!! the injection pump was redone long before the tires and getting pretty good mileage. after the tranny, pin, and rims/tires, the mileage was back at 18.

the tires went from 235 to 285 and wider rims. what is the ratio for figuring mileage now??? and I was going 65. does that mean I was actually doing 70mph or a bit more?

[dpuckett]

265/75-16s and 235/85-16s are about the same height. With 285s, you are probably going 3-4mph faster than indicated, so you were going 68-69mph at 65 on the speedo. Still not enough to account for a big MPG drop, unless it's just the increased rolling resistance.

DP

[SChandler]

The formula for calculating actual distance traveled is:

New tire diameter/old tire diameter x indicated miles driven = actual miles driven.

The formula is the same for actual speed:

New tire diameter/old tire diameter x indicated speed = actual speed. At an indicated 65, you are actually going 67.7 mph, when changing from 235's to 285's.

[T.winegar]

so like this: 285/235= 1.21

then
x miles= actual miles

[DoWhat?]

back to the tailgate thing... Thats the same idea as scuffing up the bottom of a boat with scotch brite to get that extra few mph on the top end.

The idea is that the trapped air bubbles have much less friction than even the shiniest waxed hull. My guess is it works the same way with that big trapped bubble of air in your bed. It makes sense.