an engine runs most efficiently [gas mileage wise] close to its torque
peak, which when taking into acct most big block mopars of the 60s were
rated a peak torque at 2800 [exc hi perf, then at 3200] rpm which is a nice
highway speed with the typical 3.23 geared c-body rear..
that said, with alot of driving in old mopars, i've noticed a consistent
close-to-20mpg out of a typical 318 poly- avg between cruising and highway
trips, 2 of the daily drivers - 58 + 9 - that run big block 383 and
413... are a little thirsty around town but again, with 3.23 rears, at
3000ish on the highways get steady high teens with plenty of passing power on
tap.
now, here was the amazer.... calculated about 6 yrs ago, then 3 yrs
ago, again.... take for instance a legit 440 with well over 450 hp/520ft-lbs...
run a 3.90 gear with a 28" tire in a 58 plymouth, manual 727, highway
speeds at or above converter stall.... around town, i notice about 5mpg... or
1/2 tank a night of "playing" with friends after the cruise nights....
but then i drove from the immediate NYC area to e. hartford ct...... on a little
over a 1/2 tank.... something seemed odd, so i calced the ride home.... that was
in 2001... then from NYC area to carlisle, about a 4hr ride... stopped for gas
after checkin into the hotel with the golden finners.... needless to say taching
about 4500 for nonstop hours... it gets 15mpg... amazing... and that includes a
few pulls to the shiftlight at 6700 on the highway for a few travelers who
wondered why the plates say "BAD 58".
the cam and converter kill the local driving...
and... i used to get 25mpg in a 66 valiant with 225/ stick with 2.76
gears with the top down... drove 2hr trips every 3 days in that thing for 2yrs
straight, back in the late 90s... in my college days, i cared about
saving a few bucks on gas... had some forwardlookers awaiting a buildup - even
back then..
kept gas mileage on-topic with the years on that
one!
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