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Loosing gas fast...

729 Views 9 Replies 5 Participants Last post by  Stalkingbear
My '72 Chevelle 400sbc .030 over and 435hp. At least that is what I was told when buying the car. Now, I know muscle cars weren't supposed to get good gas mileage, but my car still shouldn't be drinking gas like it is now. I have to newly rebuilt qjet on it and runs great. When the car is running, the needle in the gas gauge just keeps on moving. This happens when in "park" or "drive". It doesn't really matter. I was going to change the rear end out of it, but I don't have the garage to do it in. What can I do to get alittle better gas mileage?

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Need more info like what base & total timing are you running,do you use a vac adv on the dist,whats carb setup like prim jets & meter rods,what gear are you running,what stall in converter if running auto trans?

But your typical non od trans 400cid street muscle cars get anywhere from 5-11 maybe 12mpg on avg of that gives you any indication of where you should be. The hotter setup would be in the 5-8mpg and milder in the 9-12mpg area with poss a little better mph on open road /not in traffic cruising at a reasoable speed like 60mph.

BTW,what exactly is your mpg when you checked it? You should not go by watching the fuel gauge,that will get you nowhere esp since the last 1/4 tank almost always goes the quickest due to the fuel tanks shape having a little less fuel in last 1/4 tank as when compaier to the 1st and 2nd 1/4 tanks comming from the full mark.

You should not worry about mpg with a 30-40yr old 400 street muscle car because mpg was never a good trate of those cars/motors. The only way to get good mpg with them is to run o/d trans and to build the motor with mpg in mind too and maybe installing TPI or other EFI setup would help even more. But with no od trans of some sort you will not normally in most cases get good mpg (20-25mpg)with a street 400 muscle car unless maybe your runing 256-273 gear and have your carb dialed in on the hairy edge of too lean along with a good timing curve.

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