[Tom Wells]

Brent,

On the 460 there's a thin metal plate that goes between the water pump and the block. Seems to me there was a thin gasket on either side of that thin plate too but it's been a while.

If you leave out the plate, overheating will happen.

You shouldn't need bungs for the A/F ratio but you may need a friend with a sniffer that can be put into the ends of the side pipes. One way to tell if it's extra lean at idle is "do your eyes water?" If they do, it's often because it's too lean, not too rich. Also, if the header pipes are glowing (at night) near the exhaust ports it's likely too lean.

Burping is best done when the engine has done a heat cycle - heat it up really well, then let it cool. If you have a radiator overflow tank (which is a good idea anyway) make sure it's full before you heat cycle. Then after it's cooled off, take off the radiator cap and see if the radiator's full to the top. Even if it looks OK, see if you can squeeze a hose to try to make an air bubble emerge. If some air bubbles come out, keep squeezing and adding water in between squeezes.

Also check the overflow tank to make sure it has some water in it - water expands when hot so the overflow should be higher when the engine is warm, lower (but not empty) when cool. The idea is that if air comes out as the engine heats up, the overflow tank will provide some water to be sucked back in when the engine cools off.

If everything else is OK (no air, plate behind pump is OK, idle A/F ratio OK), then try a better fan and shroud assembly.

Tom