8-10 mpg tops for any of those engines. No real way to improve it.
Is it possible to replace the carburetor system with fuel injectors? If so, whats the price tag?
Did you try some performance headers, cold air intake, and a performance muffler to relieve back pressure?
I had a 1970 Challenger with a 340 engine it usually got 10-12 mpg, but I once got 20 mpg out of it on a 150 mile road trip, of course I didn't open the back barrels on the carb, no jack rabbit starts, accelerated slowly, shifted early and didn't drive over 60 mpg. Those are the kinds of things that will improve your mpg, but with a car like that who is going to drive slowly.
Best way to improve the miles per gallon is to put in a 5 or 6 speed with 3.73s or 3.55s in the rear end. Also is to go from carburated to fuel injected. There are companys that have kits just got to search. Mass-flow is one company, for the trans i would check with keisler as they have a drop in kit that comes with everything you need to convert your auto or 4 speed.
If your worried about the mileage that you will obtain by driving a vehicle with any of those engines you should seriously consider selling it and buying a newer 4 cylinder. none of them will exceed 9 mpg. and thats babying it and being dead on with your tune.
your getting a 1970 Challenger and your worried about gas mileage? I'll trade you for my Saturn Ion... it gets 25-30mpg lol
Yes I am sure some would ask why I would want one of these big blocks if I am worried about gas mileage. However, I am sure those individuals have plenty of money to spend on gas and other toys. However, answering the question of how to increase gas mileage while maintaining high performance at the same time is purely intellectual. Gas is not getting cheaper, but that will not stop me from getting a car like this. I am sure a lot of people will like to keep their pride and joy and be driving them ten years down the road.
I drive a 302 Mustang Cobra and yes, it hurts at the pump, but it more than makes up for it with the pleasure that I get out of driving it. I do miss my old crappy Tercel that got over 30 mpg consistently, but the experience just doesn't compare. I've wanted some muscle all my life and now they are finally affordable and I'm not looking back!
not that my opinion matters but why dont you try this... if you already own the challenger, save it for weekend drives and the occasional weekday drive, put the money you would have spent on the challenger to get better mpg, which would likely be 1500+ to make an actual difference... and buy a civic or tercell or neon or escort... here you get the 30+mpg and still get to keep you tire shredding big block for the fun days.
There is an idea. I live in the city already and have good access to public transportation, so there isn't any real need to buy that super efficient car:)
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