Mixture.. Damit!

[Broken_down?]

ok got the intake manifold gaskets in a few days ago and what a difference it made. No more sputtering at all. But now that the main problem is now fixed I have a back fire with an occational flame coming out of carb. Re-timed to 6 dg, 30 dwell, .35 gap, 700 rpm @ idle New ignition coil, points, condensor, rotor, cap, wires, plugs, ignition, belts, valve cover gaskets, exhuast gaskets. Checked for burnt valves and dead cyclinders (none), compression on all 8 was 120. Did timing from Top dead center and placed rotor to wire one etc..

Heres what happening. When I first time it, she runs great around town. Speed verys from 10 to 45 max. But when I hit the highway to open her up performance degrades so bad so fast that it starts back fireing, stalling major hesatation, serious missing to the point where the truck kinda jerks like the engine died (not sure how to explain that last one). Every so often it will backfire and a puff of smoke will come out. I am assuming this is unburnd fuel and at the price of gas that just plain hurts. When I get back I check the timing and it is still @ 6 dg and has not advanced/retarted. Plugs are not totaly black but they are working on it. I am leaning towards the idea that my mixture is way off as it does not seem to be at the "right" timing anywhere between 4 and 10 dg. Another thing and not sure if this could be or not but recently I replaced my water pump, thermostat 180 dg, radiator. Before the temp guage was very accurate. But with the new pump it takes dam near the entire day to get past the cold into the normal heat range. It used to run just above the cold mark and I knew it was acurate as I blew my alternator belt a few times on the way home from work it she heated righht up. So is there a possibility that she is running to cool?

1. How do you set the mixture?
2. truck running to cool?

Thanks for any help!


Rich