I have a 1964 valiant /6. I have replaced the carb and tuned the engine. It seems to run very well but the mileage is not good, around 14 miles to the gallon. Any suggestions on what else i might look at..thanks..ps I also check the brakes for drag and they were adjusted properly.

What did you replace the carb with? If you just got a rebuilt one from a parts store it would need to be adjusted, and thats assuming the right size jets etc. are in there.

Is the motor burning any significant amount of oil or water? How many miles are on the motor? Do you know what tranny and rear gears are in it?

14 is awfully low for a stock-ish car, something big has to be going on that you don't realize. I'm guessing carb is first culprit. I would also suggest looking at ignition, perhaps coil/plugs/cap/rotor. Upgrading to a mopar electric or perhaps even aftermarket MSD style boxes may get you a little mileage as well. My 71 duster with 3.23 rears and a *poorly* tuned GM throttle body system and clifford headers w/2.25" exhaust still gets 17-18 freeway.

If you have a catalayic converter on there (Those didn't start until 73 I believe, but its possible someone may of added it later on for emissions reasons) it may be backed up.

Electronic ignition will not give better mileage compared to a properly-adjusted, properly-maintained stock '64 system. The mileage advantage only comes when compared to an out-of-adjustment, laxly-maintained points-type system. The stock points systems were not weak by any stretch, and had advance curves better suited to economy than the short/slow curves found in most factory electronic distributors.

Catalytic converters did not appear until 1975 and were not on all Chrysler products until 1978 (US) 1984 (Canada). As a rule, they are not added onto cars that did not originally have them, 'cause just slapping a catalyst into the exhaust system does virtually nothing for emission control.

14mpg may or may not be normal for this car. How many miles are on it? Original or replacement engine, with how many miles? Does it have a 170 or a 225? Automatic or stick shift? What's the rear axle ratio? Where do you live? Do you drive mostly in the city or mostly on the highway?

This time of year in any of the many cold locations in North America, 14mpg would be completely normal in city/short-trip driving for most any 225/automatic car.

As Pierre says, "rebuilt" carbs from the parts store are usually a very bad gamble. Also, even if you rebuilt your own original carbs, certain kinds of faults and failures can be very tough to spot unless you've seen them before. Carter or Holley, on your car? Original to the car, a parts-store rebuilt, or an unknown?

Really need more info to offer meaningful help.

Time to check the distributor's advance curve and the carb jetting, it sounds like one or both are not "optimized".

Use a timing light to look at the advance, the timing mark needs to "jump" forward 10 to 20 degrees when you first hit the throttle and the total advance (springs and weights) needs to get you to 30 degrees total.

For the carb, you may want to put a "known" jet into it. If it's a Holley 1920, try a #58 to start. When the float bowl is off, check to be sure the metering block is tight.
DD

hah sounds like your getting better gas milage than me. Somewhere around 7 i calculated. i think my valiant had better mileage before i rebuilt it. before all was good i was just weary b/c of an old carb under the hood. i rebuilt it and ended up sripping 2 screws that hold the top of the carb to the bowl part. I think my carb puts more gas in the engine compartment than in the engine itself. after a drive in it you can open the hood and smell the gas. theres gas everywhere. on the intake manifold, ALL over the lower half of the carb, on the side of the block.....not the fuel pump side. Yeah its bad. real bad. but it still always starts and gets me from point A to point B.

Im tellin you. the jackpot place for sl6 parts is pick-n-pull. well, at least for northern californians. you can easily pull a supersix setup for less that 50$, clean it, and sell it for tripple on ebay. if you ever go to a picknpull your more lickley to get a supersix out of the trucks/vans. heck i got 3x2 headers (from a sportsman100 van with a 1bbl..yeah it didnt make sense.) for 25$!!! ( i argued that its a one piece header deal because of the engine untill they finally let me have it, else it wouldve been 50$). Disk conversions are another big one too. i got my front set up, spindles, capilers, rotors, well the best rotors i could find and got them turned, a arms and prop vaulve all for almost 90$. my best find though was a 3.23 posi with 10x2 1/2 ( i think) drums from this 79 magnum for 80$. At Pick-nPull parts are parts they could care less what car they came from or its value. this could be good or it could be bad because of the ocassional rip offs. i go pretty much every weekend. if anyone else wants to go tear up old mopars let me know.

I strongly disagree with this. I've had points/stock ignition/MSD on the same engine and they don't perform neither behave all the same. While I don't buy the "more powerfull spark" argument, I simply cannot accept that points will stand to any kind of electronic ignition in practice. The theory may stand for this, but theory is theory and getting the hands on stuff is a whole diffrent story. To me is like "carbs are as good as multiport EFI". I do prefer carbs, but a properly tuned EFI is way more efficient. I've checked and stock electronic ignition gave me 10-15% mileage improvement over well maintained never neglected points, and MSD gave me mostly idle and part throttle improvement (very noticeable) and another 5% mileage improvement.
that's true, but fixable if you recurve the electronic dist.

I'd look for
--slippage in tranny (if it's an auto)
--clutch wear if it's a manual
--wich gas grade are you using? sometimes if you use higer grades gas you'll en up trading gallon price per mileage. I.E. when I use 98+ premium I get 3 to 7% more mileage than 95 octane gas. I keep very accurate track of my fuel consumption and I'm not shooting in the dark, I have spreadsheets that back up this affirmation.
-- rear axle ratio? if it's too low it may kill your town mileage.
--tires being underpressured?
--of course, carb and its accesories like choke, air filter element, etc.

_________________
Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

I get around 10mpg around town, but 20+ on the freeway. I have 2.45 gears and a 4 speed. The engine is properly tuned up. My commute is 6 miles round trip. There are 5 stop lights and the road is nice and level. It takes me longer to warm up the engine then to make the commute. My gas mileage is sucked up waiting and accellorating away from stop lights.

Most \6s get around 17mpg. Some get better and some get worse. A \6 is an "economy" engine only compared to comtemporay engines. The big blocks would get around 10mpg and the small block blocks around 14. If you want great mileage, buy a new car. There is no comparison between the old slant and moderan computer managed engines and powertrains.

Hey Kesteb

I get around 10 mpg too in town, with 3.07:1 gears and a 904. I double that mileage when cruisin @ 70-80 mph.

i'm agree with you about the "economy" thing... I guess that having so much fun drivin a car has to have some tradeup... but hell, I love to drive my old dodge around everyday.

_________________
Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

i have the 170..carb was a rebuilt carter from advanced auto...it ran much better with the new carb other than the coke setting is off some..im thinking the timing is a bit off