So in my 72 Duster with a 3.23 rearend, 1406 edlebrock and an overdrive 5 speed I should easily hit 20+? I'm hoping for 25+ on the highway but 20+ would be great too!
Tune that carb right and you will see that easily especially with a 5 speed.
Edelbrocks can be tuned for decent mileage. I used an AFR gauge with mine.
I'm using a more advanced version of your 1406 (#1806 650 AVS)
I get 17 mpg on the freeway with my Duster but it has a non-LU A999 auto. (I get about 13-14 around town) BE EASY on the secondaries.
Get froggy on the throttle and you'll see the mileage drop like a bad date.
I'm currently rebuilding a thermoquad, would be very interesting to see the difference once I'm done and tuned with it.
*Edit* PS: Make sure you use a clutch radiator fan not a solid mount flex fan. (Or maybe a good electric one if your inclined to do so).
