What kind of mileage are you guys with stock small blocks getting? My '67 has a 327 with a re cured HEI and a Edelbrock performer intake with a Holley 600 carb,single exhaust, powerglide and 3:36 gear.I'm getting 10 mpg on the highway.That seems low. I would expect 14-16 mpg.I just came back from a show(100 MILES) with a friend that has a BUILT 402,4speed and 3:73 gears and I burnt more gas than he did.

Back in '66 I had a 283 Beaumont that couldn't get over 20 mpg (Imperial) on the highway. Friends with their stick shift 275 hp 327s were typically getting 23-24 mpg (Imperial) and blowing my doors off at the same time. There is no reason that a mild, well setup 327 or 350 can't get 20 mpg US on a highway run. Overdrive could improve on this. I'm all ears on this as I'm doing a '69 el Camino with a mild 350, turbo 350, and 2.56-1 rearend. The next step will be a '94 LT1 and 4L60E, which would be an all around nicer combination with proven performance and gas mileage.

the powerglide and single exhaust are hurting your milage

I would say the Chevelle gets 10-12 city and 14-16 highway, the other car is about half that.:yes:

put in a TH350, and the car will perform better in every respect. i think that a powerglide has a higher stall converter to make up for a crappy first gear, and with mild gears, it never really "locks up" at highway speeds.
another thing- either recalibrate that Holley to run leaner in cruise mode, or just throw a rebuilt q-jet on it.
buy a vacuum gauge to mount under the dash, and learn how to properly drive a car for mileage. a vacuum gauge will move every time you move your foot on the gas pedal- which is more than you think- and you will learn to make then needle stay nice and steady when cruising down the road. the gauge alone is worth a couple of mpg, and quickly pays for itself in gassavings.

I was getting 15+ going back and forth to work. I could get ~18+ mpg on the highway. That's with a 327, 3.08: rear gears, Qj, and a thm-350. The powerglide shouldn't hurt you on the highway compared to a thm-350 as they have the same final drive ratio.

Once I got my favorite Qj dialed in, I could get 17 mpg going back and forth to work.

Bottom line is that you should be able to pick it up quite a bit.

Here is a link to a test that I ran between a small Holley and some Qj's.

http://www.chevelles.com/forums/showthread.php?t=72047

Best Regards,

Mike

What's a re cured HEI? Got vacuum advance?