Would converting my '64 Valiant to EFI from a Holley 1920 increase my mileage significantly? I am currently getting 14mpg with all systems tuned up.

Most of the conversion kits cost between $1000 and $1500 (Turbocity TBI setup) . You may gain a couple of mpg after the conversion. You do the math and figure out the break even point. My feelings is that you could buy a lot of gas for that amount of money.

You will get between 10 and 30 % increase in mileage by going to TBI over a stock 1bbl, depending on your state of tune. While Kesteb is right that you will never recoup the money in fuel cost alone, your car will run more reliably and cleanly, and have more power with a TBI. EFI would be more expensive with multi-port injection, but the gains will be greater as well.

My 2 cents,

Lou

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Home of Slant6-powered fun machines since 1988

14 MPG is pretty low for a good running SL6, a good working Holley or Carter bbs should get you 18 to 20 MPG.

Change to a well tuned EFI and add another 2-4 MPG
So if you were getting 22-24 MPG and the car ran better, would that be worth the $2,000 conversion cost? (or cheaper if you do most of the work yourself using "boneyard" parts)
DD

The car has a carefully rebuilt engine with 5000 miles on it. The Holley carb was rebuilt by ReCarbCo, the engine is carefully tuned, and valves adjusted. I just can't seem to get more that 14mpg out of it. Mileage did drop when I swapped an old Carter carb for the simpler Holley. I'm thinking of reinstalling the Carter as an experiment.

Uhmmm, rebuilders tend to put in bigger main jet(s) to help driveability, they figure it would take the customer longer to figure out the bad MPG then it would if the carb had a stumble, flat spot, lean surge, etc.
BTW, don't trust the number stamped on the brass jet, many times the rebuilder just drills them out to an unknown larger size.

You may want to pop-off the float bowl and change the main jet. This will give you a chance to check to see if it is loose (yes, I've seen the jet loosen-up and even fall out into the bowl) and you can put in a known size.
For a Holley 1 bbl, a #54 jet is pretty lean, more then about a #60 (at sea level) is wasting gas.
DD

My '69 Barracuda with multi-port EFI (see "articles" section) gets 16 MPG with a "heavy foot".
Bob D

My 250 cube 200hp EFI Ford six gets 22mpg around town in regular use.

Also, if you are talking 14MPG of purely city driving, that isn't too bad. Most econobox cars don't get better than about 25 in true city driving, especially if on short trips.

Lou

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Home of Slant6-powered fun machines since 1988

This morning I discovered the source of my low mileage. I have a small fuel leak where the sending unit exits the tank. I did notice that the gauge went down very fast after a fillup. So my true mileage is much better than 14mpg. Thanks for the replies anyway.

When I was investigating a fuel delivery problem on my '79 300, I found the filler neck to tank grommet dry rotted and cracked. They are pretty cheap, I'd replace that, too, while your in the vic.

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'66 Cuda 225/4spd
'66 Dart GT convertible 225/auto
'64 Dart GT 340/4spd

the savings with efi go a bit beyond the gas pump. properly set up, engine life will be extended since there won't be excess fuel washing the oil from the cylinder walls, also plug life should be extended as well. carbon buildup, however, will never go away but should decrease a bit as well.

-james

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