Re: [Amc-list] Days of Whine & Roses

[Frank Swygert <farna@xxxxxxx>]

My J-10 w/258 delivered an average of 20 mpg driving from Delaware to SC with a 800 pound load in the back and towing a small trailer weighing about 2000 pounds (trailer and load). But it's a four speed stick with 2.73 gears. First could be a little lower but fourth is like overdrive. And this was with a leaking intake manifold and a carb that needed rebuilding. But that was nearly all interstate driving. 

Now with the 390/4V and 4.0L head I'm averaging 18 mpg in rural and city driving. No long stretches on the highway, and what is there is a bit on the hilly side (near a lake). I think it would get 22 or so on the interstate on a long trip. Power is okay, but you don't want to pull a heavy load with it. 

The 360 can be built to get decent mileage in something like a full size Jeep. It takes a lot of power just to get the weight moving, then you have the big flat frontal area to push through the air. If it were streamlined the six would do better, but with all that frontal area you're working the six a bit just to move the darned thing. 

Gearing, tire sizes, and other mods greatly affect mileage. My nephew keeps telling me I need bigger tires to fill those big wheel wells -- the truck would look better. My first answer is if I were worried about looks I wouldn't have bought an old Jeep truck from NYC with some rust issues! The second answer is it's just got adequate power with 215/75R15 tires. Put bigger ones on and they would kill power! If anything I'll put SMALLER tires on it. I'm thinking about 215/70s because anything smaller really would look tiny in those wheel wells, but might go with a 225/65 or even 205/70. A little smaller diameter would actually help by giving it a bit more pulling power. It really needs 3.08 or 3.15 gears, 2.73 is really too low for anything but the interstate, and it wouldn't hurt to have lower gears there too. The low gears keep the engine loaded, which isn't always good for gas mileage. 

The main point is I bet I could build a six that would get better mileage than a 360, even if the 360 were built for it. I think that an EFI 4.0L would out-do a 360 if installed in an FSJ and geared right. The 3.08s used with the Cherokee/Comanche are too high, but I would think 3.31 gears would be a good compromise between power and mileage. Hmm... I wonder if Cherokee axles are wide enough for my J-truck? 3.08s would be cheap enough then... 

-------------
Date: Tue, 17 Jun 2008 01:51:37 -0400
From: Brien Tourville <hh7x@xxxxxxxxxxxxx>

I'm having 'Issues' :
$5.00 Gal. Gasoline / 20 Gal. Tank = $100.00.

Googled up the AMC 360 V8 today wondering of best
mileage achieved - ran across JEEPers talking 360 vs 258
mpg comparisons.

Surprisingly, the 360 between 13 - 24 mpg with the
258 at 14 - 21 mpg.

Not written in stone - some had swamper 31" etc. -
but general consensus held a 360 V-8 could deliver
better mileage than a 258 I-6 for varying reasons.

The 2bbl. 360 made less mileage than a small primaries
4bbl - and less power.

-- 
Frank Swygert
Publisher, "American Motors Cars" 
Magazine (AMC)
For all AMC enthusiasts
http://farna.home.att.net/AMC.html
(free download available!)

_______________________________________________
Amc-list mailing list
Amc-list@xxxxxxxxxxxx
http://splatter.wps.com/cgi-bin/mailman/listinfo/amc-list