gas mileage Mechanical vs Vacuum Secondaries

Mileage is mostly in your right foot.

350hp 360 with a 2500 converter and 3.00 gears got 20 mpg on the highway with an out of the box 4779 750 DP, no jet changes. I thought that was pretty good.

In my experience with the proform vac sec main bodies, you better have some air bleeds handy. Most chrsyler SB applications will be too lean at cruise, where the air bleeds and Idle Feed Restrictor play the biggest role.

If you want a good primer on tuning for cruise and part throttle applications, go to the innovative motorsports site and look at the tuning articles.These are the people that have the LM1 O2 reader out there.