[Amc-list] Re; Mileage

["John Elle" <johnelle@xxxxxxxxx>]

Armand
Snip
Funny part about all this is when I bought the car as a kid in 72, it
would
routinely do 18 mpg on the highway.
Snip
I bought mine as a one owner  1977 late model used car about 1982 or 
so with about 56,000 miles on it. It was a California smog car. It never
got any better than 12mpg, although I applied a number of tuning tricks
to it that were guaranteed to improve the mileage and eventually I was 
able to improve it all the way up to 9 mpg. I backed everything off and 
settled for 12 for the rest of the ownership. I did some research from 
that point on and bought some 1970 parts like the distributor and the 
carburetor and a few other bits and pieces and compared them to 77 
parts and they were identical. I never really did find a real reason for

the 12 mpg but I became really suspicious of the cam being the prime
culprit. By that time I had installed an Iskenderian cam in my Donohue
and was trying to work up the ambition to swap the used 70 390 cam 
in the 304 to see what it would do for gasoline mileage when I got a 
chance to sell the car for good money and did so. 
The truth is though that I never really had a 2bbl V8 car that got gas 
mileage worth a darn. I had a Chrysler 2bbl 383 prior to that and it
would get 14 or so on the open road. And before that I put a lot 
of miles on a Plymouth Belvedere 225 slant 6 w/auto that did not get
very good mileage either but after I bored it out .100, installed an
Isky
cam and a set of Jahns pistons for 13:1 compression and a Carter 
465 cfm 4bbl it would get 20 mpg out on the freeways.
The Matador was about the fastest 2bbl carb engined car I have ever
driven though and I put another 50,000 miles on it in the 2 years I 
owned it driving it everyday.
Snip  
By the early 80s after I'd rebuilt the carb, it dropped off to maybe 16
mpg
on the highway. Remember these
figures are with the slush box automatic in it
Snip
Mine was a 998 car too and all in all except for the fuel mileage it was

a pleasant car to own. 
 
The Donohue gas mileage went from aprx. 15 or so to a solid 21 on 
the highway and out on the open plains pushed a bit would clock 19 
with no problems at all. I am a great fan of the Mustang t5 bolt in on 
an AMC car and am about to do a second.
 
I have always felt that the "Economy" versions of Detroit engines 
were rather cheap to build and economy was an illusion. The I-6's 
and the 2bbl v8s were so down on power and under carbureted that
when flogged it was all they could do move the dead weight down 
the road. My experience has been over the years, put a good
performance cam in them (do not over cam them) and move the 
HP  band up in the rpm range you did not flog them as hard 
and economy would improve and then install a 4bbl which will 
run on smaller primaries than a 2bbl is, the economy would jump 
again. But the car still had oomph behind it. 
 
I have built a couple of horse power I-6 cars that were quick 
enough but fuel mileage would improve like mad with them too. 
 
Anyway, that has been my experience. 
The 360 I am building for my Hornet will be a 2bbl car I guess
'cause I have the parts. Maybe I'll have to see how it runs. 
Later. 
John. 
 
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