gas milage

[66StangGuy]

with my current setup what do you think my gas milage should be? This is without having a led foot. My vaccume gauge reads 15" at idle in gear and 18-19 in park. My secondarys come on at 5" or less. when i push the gas pedal it is easy to get the vaccume to drop below 5" causing the secondarys to come on. is this normal for the vaccume to drop this easy or am i just trying to go too fast? also any tips for getting better gas milage. timing and carb is setup already.

what spark plugs do you reccomend?
what t. stat should i run?

Would my exhaust be a problem with the fact that thers hardly any backpressure from the exhaust being pretty short and straight?

[66fastback]

forget about the mileage and put your foot in it!! Do you really expect to brag to your buddies that you get xx mpg??

I gave up a long time ago....it didn't matter if I had stock exhaust, intake and carb....... or aftermarket headers, cam, intake and carb (Holley or Edelbroc), I always got about 14 mpg around town, and 16 on the highway. It never really mattered if I drove it like it had an egg under the pedal, or if I tried to keep it pegged to the firewall.....14-16. Always.

OK, maybe the extremes were more like 13-17, but it was always about the same. This comes from years....YEARS of driving old Stangs. It never really made much difference to me if it was a stick or an auto tranny either. The best mpg I ever got with a carb (daily driving---not on a trip) was probably 17-18, but that was with the 5 speed.

Even now I get around 20, but that's with fuel injection and a 5 speed. Sorry, I'm rambling on. My best advice for good mileage is keep it tuned up, and install a vacuum gauge (it sounds like you already have one). Try to keep the vacuum above 10" or so when driving, this will keep the power valve closed, and keep you from wasting precious fuel.

Of course try hard to stay above that 5" mark to keep the secondaries shut....you know the big drain on the tank that goes along with it. Of course, opening up the secondaries is the best thing about having a carb.

[Rev]

My set up is fairly similar to yours except that i run a 3.25 instead of a 3.55 axle. I use TFTW heads and a CC268 hydraulic cam.

Mine gets 14 mpg with me not being very careful. After all, secondaries are meant to be opened aren't they? We don't want the gas in the secondary float bowl getting old do we?

I would run a 180 thermostat for all around driving. I also would just run the stock recommended plugs for your heads. I personally like AutoLite. Don't worry about not enough back pressure. The less the better. You won't need back pressure to make torque.

Rev