okay, friend and i have an 85 econoline w/ the 300, carbeurated. the enigine was using more oil than gas, and had compression in the 50's, so we bought another engine to put in, out of an 84 econoline (the engine had been sitting for about eight months, but ran when it was parked). we kept the carb off our running (though poorly) engine, to eliminate any problems that might be a carb out of adjustment.

we finally go the engines switched out. we kept the ignition off our 85 (the duraspark II), and we're tried setting the initial timing. after cranking and starter fluid, the engine will eventually kick, but then will (for lack of a better word) "backfire" through the carb, more specifically a pipe coming out of the base of the carb, about 1/2 inch in diameter. sometimes it's just smoke, twice it's caught the residual starting fluid/gas on fire (small fire, small enough to blow out with your mouth).

our thinking is this: the timing is too early, thus sparking while the intake valve is still open. but this is the only distributor position we can get the engine to kick at all in.

what makes it more complicated, is that the distributor has a nipple on the base of it for a vacuum hose. i was told this is the advance timing vacuum hose. we can't figure out where this hose goes.

also, there's a vacuum nipple (though a different size) on some sort of manifold and we can't figure out what it goes to, either. it's the thing the carb bolts to, right on top (or perhaps part of?) the intake manifold.

help for a couple of guys who bit off more than they could chew?

thanks!