I know that this question has popped up somewhere in the past...but whats the average gas mileage on a holley 1920 on a bonestock 225..seems i only get like 11 miles to a gallon "thats goin downhill with the wind to my back"...and could wide back tires be helping this gas problem along???? just wondering. Thanks DB

I was getting 18 mpg on a holley 1945 on a stock slant, your tires look to be close to mine and they make almost no diferance that i can tell

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Even in moderation i am excessive!

This is one off my "standard" replies. There could be many problems there, but something is wrong for sure. Your choke could be stuck, or the power valve could be open all the time. Your timing could be way retarded, or your vacuum advance not working. That 18 MPG figure is pretty typical, but in the 20's is not uncommon. I have gotten mid 20's with a stock duster in the past, just well tuned.

One commonly ovelooked component is the ignition wires from the alternator clear through the ampmeter, ignition switch, and then to the battary and on to the ballast resister. On a car that old the connections are going to be pretty crusty, and will loose power and efficiency there. Measure the voltage at the battery while it is running, and measure the high side of the ballast resistor. You should see less than .5 volts drop. My Dart, when it was stock went from 13MPG to 18 MPG by changing the connectors on the blue wires under the hood and dash. This meant clipping off the old one, and soldering on a new one. I cleaned up the bulkhead connector too. Just start at the alternator wires, and follow them along to the voltage regulator and bulkhead connector, and replace each connector as you come to it. It's a pretty cheap thing to do, with very positive results. If the ampmeter is bad, and you are loosing voltage there, you must either replace it, or bypass it and install a seperate volt meter to keep track of the charging system. I like the volt meter system better anyway. Good luck. Keep that car going.

Wider tires do cost you mileage, but my Corvette got 22MPG average with 285's on the back. It should be possible to get good mileage with those tires.
Sam

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Another common one, if your idle seems a bit rough, is tight valve lash. That will destroy mileage.

Lou

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Home of Slant6-powered fun machines since 1988

Have a look at this thread for some ideas.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Sam,

Where did you source replacement bulkhead connectors? I've got a couple cars with questionable wiring, and those sure would be nice pieces to come up with.

I honestly do not recall if I replaced those or just uncrimped them, polished them up, and then soldered the wire in place. It's been at least tne years since I did this, and much has changed on the car since. I did solder everything. I know there are those who think a solder joint will eventually fail, but to me it still seems better. You might be able to get these pieces from Year One. Someone makes them for sure, because they would be on the end of the new harnesses that Year One sells.

Of course the bulkhead connector block itself is not a part of the circuit. It just holds the male and female ends of the two wires together.
Sam

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and remember; today's crappy gas doesn't lend itself well to good mileage! $3/gal don't help either.