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There's a lot of variables at work here ... vehicle load, headwinds, road conditions, traffic, and road speed ... which may have adversely affected the 250 - 6 fuel economy on the 300 mile trip.
A friend who had his whole family driving Chevy's with that motor, ever since the mid 1960's ... used to brag that he got better fuel economy in town and on the road than the aircooled VW bug's of the era. Getting into the low 20's with his Nova's was not a problem on the road, even in the early 1970's era cars. That was driving fairly moderately ... never over the speed limits ... and in nice weather. Should also mention that that was based in Denver, where there's a handicap due to the altitude for fuel mileage.
In dead stock trim, the 73 engine was a pig, pure and simple. If the Nova had an automatic and something like 3.54 or 3.73 gears in the rear, averaging 14 MPG is probably realistic.
I think you are digging these numbers up from your stash of old Consumer Reports magazines, right?
The 250 can be made to get a good bit better mileage than the '73 model did right out of the box.
This engine benefits a good bit, I have heard, from an aftermarket intake and set of headers, apparently the fuel mixture distribution is not so uniform, and the exhaust manifold certainly does not look like a good high-flow design.
The Chrysler slant-6 has a better intake and exhaust manifold set right out of the box, IMHO.
I've heard people talking that their inline 6 Chevys were getting 20 mpg.
You didn't mention if your Nova has the 2 speed powerglide....or the TH350....or the 3 speed manual....for sure it probably has a 2.73 rear end under it.
1973 Nova 4 doors weighed in at somewhere between 3169 to 3209 curb weight, before any options were added, as per this Nova website: NovaResource.com - Nova Weights
I've heard people talking that their inline 6 Chevys were getting 20 mpg.
You didn't mention if your Nova has the 2 speed powerglide....or the TH350....or the 3 speed manual....for sure it probably has a 2.73 rear end under it.
1973 Nova 4 doors weighed in at somewhere between 3169 to 3209 curb weight, before any options were added, as per this Nova website: NovaResource.com - Nova Weights
I don't have any data in front of me, but I would expect the 250 to get a higher numerical gear than the 2.73. Certainly in older GM trucks with the 250, they got something like a 3.54 standard.
Depending on how you drive one of these, a "too tall" gear might have you dropping manifold vacuum down to the point where the power valve opens (crude enrichening device found on carbs for you kids who have known only FI) and actually get worse mileage than a small V-8 like the 350.
My sister had a GM truck with one of the last versions of the 250, the one with the integral intake and head. Bad move, should have had a V-8 - the truck was slow, but not particularly thrifty, and the A/C was in the way bigtime when changing spark plugs.
The earlier versions of the 250 were a good engine though, if you go back to say 1965 and look at *that* Nova (Chevy II) with a 250 and maybe even a 4-on-the-floor...sort of like the 325i BMW really, but simpler (and cruder, of course)
Would you consider a normal range of 10-18 mpg and an average of 14 mpg on a 300 mile trip to be bad economy for a 73 Chev Nova 250 6?
By contrast a Valiant 225 6 clocked in at 12-23 and 18 on a trip; a Duster with 198 6 was 13-27 and 23 on a trip
if the Nova was bad, how bad do you see it as being?
there are a lot of performance modifications that will increase your gas mileage. first, get a tune-up. some modifications that will increase your gas mileage include:
performance ignition components
performance exhaust components such as header(s), and a flowmaster muffler
if youre using an air filter, a K&N air filter might help a little bit.
these modifications should give you a couple more miles per gallon and your car will run better too.
I don't have any data in front of me, but I would expect the 250 to get a higher numerical gear than the 2.73. Certainly in older GM trucks with the 250, they got something like a 3.54 standard.
Accroding the that site, a 250 in a 1973 Nova received a 3.08 when paired with either a TH350 or a powerglide.
Lowest gear ratio for that year was a 3.42 when you ordered a 350 powered Nova with a 4 speed.
FWIW my 69 Nova came factory with a 230 inline 6, powerglide and a 2.73 rear axle. Those little 6's are torquey.
Integereal head....believe that started in 1975.
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