So I finally took the rig on a long enough trip where I could clock the mileage. The stock 2bbl carb (Carter BBD I think) is adjusted for where I live (at 5000 feet in Fort Collins, CO) - drove it up into the mountains (up to about 8000 feet) and then hauled a load of stuff back to Fort Collins (about 200 miles round trip).
Between having it floored (to maintain 55 on the highway) from about 5000 to 7500 feet (for about 15-20 miles) and then hauling a full load of stuff back to Fort Collins (maintaining 55 to 70 mph) I averaged 13.6 MPG.
Now comes your opinions, should I keep the 2bbl since the mileage was pretty decent OR should I (rebuild and) install the Holley 4160 and 4bbl intake (intake is a stock mani off of an '81 318/360)? I know it will give it more power, but I think the mileage will suffer. Thoughts?
And as always... :dtrocks:
fal308
06-09-2008, 01:41 PM
Mileage will vary depending upon how heavy your right foot is
doodlebug
06-10-2008, 08:08 AM
I honestly don't think you'll improve much on that as far as mileage is concerned. If it's running good right now with the carter carb, I think I'd just leave it on there and put that money in some other areas. BTW, I was looking at your photos and enjoyed seeing the progress you had made on it. Keep up the good work. :)
Dodgevanman
06-10-2008, 11:57 AM
In these days of $4 and $5 gas, I'd leave the 2bbl. on. Just my .02
86_custom
06-10-2008, 01:03 PM
I thought a good tuned 4bbl gave better mileage, if you could resist the little bit of extra power
scargo02
06-11-2008, 12:46 AM
Mileage will vary depending upon how heavy your right foot is
Very true, but it seems like bigger carb = more CFMs = more fuel used, no?
I honestly don't think you'll improve much on that as far as mileage is concerned. If it's running good right now with the carter carb, I think I'd just leave it on there and put that money in some other areas. BTW, I was looking at your photos and enjoyed seeing the progress you had made on it. Keep up the good work. :)
That was my thinking...the more I think about it the more I think I'll stay with the current setup.
Thanks for taking a look at the pix...I really need to get started on the body work and get it prepped for paint!
In these days of $4 and $5 gas, I'd leave the 2bbl. on. Just my .02
Exactly...regular is creeping closer and closer to $4 here in Colorado.
I thought a good tuned 4bbl gave better mileage, if you could resist the little bit of extra power
I've read that quite a few times on here but still have yet to see any hard proof either way.
swami2806
06-11-2008, 10:40 PM
4 barrels will do just as well as 2 bbls gas wise as long as you don't let the extra 2 barrels kick in. Normal driving you're on 2 barrels anyway.
scargo02
06-11-2008, 11:24 PM
4 barrels will do just as well as 2 bbls gas wise as long as you don't let the extra 2 barrels kick in. Normal driving you're on 2 barrels anyway.
That's true, but what CFM is the Carter 2 bbl rated to? How many CFMs flow through the primaries on a 4 bbl, 600 CFM Holley? Isn't that what really matters, or not? And with the extra 2 barrels it seems like that's just temptation waiting to happen...I'll hang onto the 4 bbl carb and intake but I think I'll remain with the 2 bbl setup for now.
bherder
06-12-2008, 09:23 AM
Hey, 13.6 mpg from a full time 4x4 is not all that bad....Better than mine... I'm not sure if a carb swap will do any good.... On the other hand, Doodlebug and myself managed to squeeze out about another 1.5 mpg by installing an electric fan.... just keep in mind that fuel economy was never a consideration when our rigs were built. (If it was, they didn't try all that hard.. :D )
fal308
06-12-2008, 09:43 AM
The reason you hear of four barrels getting better mileage is that the primaries are usually smaller on four barrels than the primaries on a two barrel. So if you can drive without opening the secondaries, you'll use less fuel and get better mileage. The secondaries provide extra fuel, thus more power, when needed.
scargo02
06-13-2008, 10:43 AM
Hey, 13.6 mpg from a full time 4x4 is not all that bad....Better than mine... I'm not sure if a carb swap will do any good.... On the other hand, Doodlebug and myself managed to squeeze out about another 1.5 mpg by installing an electric fan.... just keep in mind that fuel economy was never a consideration when our rigs were built. (If it was, they didn't try all that hard.. :D )
Oh I understand fuel economy wasn't a consideration, believe me! Compared to newer trucks they're basically a very square-ish box in the wind at highway speeds! :D The electric fan conversion might be next on the list if an extra 1.5 MPGs is the case!
The reason you hear of four barrels getting better mileage is that the primaries are usually smaller on four barrels than the primaries on a two barrel. So if you can drive without opening the secondaries, you'll use less fuel and get better mileage. The secondaries provide extra fuel, thus more power, when needed.
Got'cha!
AMP762
06-15-2008, 07:44 PM
If I could get 13.5 out of mine I'd be a happy camper.
mikehopkinsjr
06-15-2008, 08:24 PM
Well, another thing is the front of our trucks are flat like a brick wall, air is gonna slow us down and burn gas.
bherder
06-15-2008, 11:20 PM
Hee hee hee .... Not as bad as my ol' A-100 van though.... That was about as areodynamic as a billboard.. :D :D :D
doodlebug
06-16-2008, 01:06 PM
Yea, I use to drive with my left arm/elbow hanging out the window. Now I've quit doing that to try and cut down on drag. :D Hey, with these prices I'll try anything! :dunno:
