Live: V8 MPG

[slvrbck]

I have a basic 40, GM crate 350 w/ truck avenger, sm420, 4.10s and 35s. I carry a pretty decent amount of gear, especially when we are going to a ride. I generally get around 10, best was 13.8, worst was probably 8. I need to put the injection stuff on and put in an auto trans.

 

[misterpepper]

What about a gas leak?

 

[cmiller114]

if I start at the top of the hill at 60mph, and let off the gas at any point in the slope, given enough time (maybe 30-45 seconds) without touching the brakes, the rig would slow to a 1st gear pace.... I dont hear any dragging or strange noises during that time, and if I put it into neutral, I coast as expeceted, which i would assume rules out brakes dragging.... when I leave it in drive and coast it feels as though you were in too low of a gear for the speed and it just gradually pulls you down to the right one (and proceeds to shift down to 2nd and 1st gear until you are creeping along)....

Sounds like the vacuum modulator is not working or not installed correctly. Could be as simple as a loose vacuum line to AT.

 

[Splangy]

uh, you call your truck a "he"?

 

[90 Weight]

Some great guys out of the Ashland/Medford area have offered to help me look into some of the issues out of their garages- I'll post up with any updates this afternoon.

Sounds like the vacuum modulator is not working or not installed correctly. Could be as simple as a loose vacuum line to AT.

This sounds probable...I'll check.

uh, you call your truck a "he"?

"Clifford"

Deliberate Forager - navigate to the meet clifford section for explanation

What about a gas leak?

hope not- and havent seen/smelled anything.

 

[JB740i]

Sounds like the vacuum modulator is not working or not installed correctly. Could be as simple as a loose vacuum line to AT.

Isn't that moot? If he put it in neutral and it slows to a near stop going downhill shouldn't it be a brake issue? Neutral is neutral vacuum line or not?

 

[FJforty]

Have we ruled out the trailer slowing you down?

 

[bikersmurf]

Trailer?

Currently in the midst (first 6 days) of a 70 day, 5,000 mile roadtrip in the 40.... This is the first major driving he has seen and so I was not exactly sure what MPG to expect....

he has:
new crate 350 w/edelbrock 4bbl 600cfm

three speed automatic TH350

33x12.50's

Hardtop w/roof rack and RTT

Tire carrier

and a FULLY FULLY loaded cargo area.....I mean to the cap fully loaded....

I was expecting something around the likes of 12-15mpg....


drum roll.....


after 600 miles, we are averaging 5.7MPG

is something wrong? should I check the tuning? he is running fine but maybe he could be tuned for economy? or do you guys think that should be expected for a fully loaded flying brick?

On open stretches I keep the rpm's somewhere between 2500-3000 on the top end (60-73mph) but the majority of the driving has been along the PCH (california coast line) so the speeds are up and down hills at around 35-50....

what do you guys think?

Perhaps I've missed something.

 

[Volcanic Iceberg]

What about a gas leak?

Welcome to MUD misterpepper!

 

[1Fine40]

Just a small observation, and probably not much, but how much air pressure are you running in those tires? That makes a huge difference in my mileage when I travel in the 40. The other thing I was thinking is what weight/type of oil are you using in the motor? 10w40 dino oil will cost you mileage vs. synthetic of the same weight...perhaps a 10w30 synthetic once the motor is fully broken in will also help out tremendously...my mileage increased in the 1 to 2 mpg range with synthetic 10w30 after appropriate break in using 10w40 dino....

Cheers!

 

[90 Weight]

haha nice catch Iceberg.... welcome misterpepper.

ok- made a bunch of progress thanks to the help of some great guys out of the ashland/medford/yreka area.

the truck doesnt slow down when you put it in neutral, which rules out brake issues.

at this point I think it may just be compression braking that I experience when letting off the gas going down hill....

the weakened brakes were in part due to the wheel magnets rubbing on the caliper and for the most part nearly absent front pads... will be fixing that promptly

the truck is definately running very rich so I'm going to try and fiddle with it myself (just lean it out a bit) until we stumble upon someone who knows what they are doing with carbs.

with the brakes fixed, a spare tire, newly acquired water and jerry cans- we are going to be headed out on the next leg of our trip into the oregon backcountry via the "Backcountry Discovery Route" from crater lake to bend all via old dirt/government roads.

thanks for all of your help guys. I'll keep my buildup thread and blog up to date with trip details, movies and pictures.

cheers.

 

[Hugh Heifer]

haha nice catch Iceberg.... welcome misterpepper.

ok- made a bunch of progress thanks to the help of some great guys out of the ashland/medford/yreka area.

the truck doesnt slow down when you put it in neutral, which rules out brake issues.

at this point I think it may just be compression braking that I experience when letting off the gas going down hill....

the weakened brakes were in part due to the wheel magnets rubbing on the caliper and for the most part nearly absent front pads... will be fixing that promptly

the truck is definately running very rich so I'm going to try and fiddle with it myself (just lean it out a bit) until we stumble upon someone who knows what they are doing with carbs.

with the brakes fixed, a spare tire, newly acquired water and jerry cans- we are going to be headed out on the next leg of our trip into the oregon backcountry via the "Backcountry Discovery Route" from crater lake to bend all via old dirt/government roads.

thanks for all of your help guys. I'll keep my buildup thread and blog up to date with trip details, movies and pictures.

cheers.

Be safe and have fun!