[Ivan D.]

Matt, I know the feeling very well - my 2wd C10 with a relatively fresh engine (with ported heads too) never gets more than 10mpg, no matter what I do or how I drive. 350 engine, 350 tranny, 3.08 rear gears, 33" tires, and a double-pumper Holley with no vacuum leaks. I have done pretty much everything possible to that thing - jets are so small you can't even buy them aftermarket, and the secondaries delayed so much that to have them open when passing someone I should have jumped on the gas yesterday at the same time. I have tried three different primary power valves, and the only thing that happens is loss of low-end power. I have had the base timing anywhere between 8 and 12*BTDC, and the distributor hooked up to both ported and manifold vacuum - mileage don't care at all, however running at 10* base and manifold advance seems to remove the idle-1000rpms hesitation and improve low-end power. There's just no winning over that truck, only thing I can do is floor it more often so at least I get some fun for all the gas I put into it.