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Problems after a stock carb swap

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Just put on a new (to me) junkyard carb and blocked off the EGR and what nots on a 77 l20. The carb came off another truck, is externally identical and initially ran great. That lasted a week. Under load it cuts out and dies. Im Guessing vacuum, somewhere in my previously used gaskets and hand made block off plate. I had it idling for a minute and no poking or prodding around the plate changed any thing, and the carb is bolted tight still. Anything stupid/basic/obvious I might be missing before I tear this thing off at work?



Edit: Getting fuel to the carb (new filter and pump 3 mos ago) EI dizzy, still fires

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If it idles it won't be a vacuum leak.


While idling check the fuel level in the sight glass on the front. If low or not showing the float may be set wrong.


Take it for a hard run. When it dies get the clutch in (or shift to neutral) and the key off as fast as you can. You want the engine stopped ASAP to preserve the condition of the carb when this happens. Do this on an empty road. Roll to a stop and check the sight glass on the front of the carb.


If full to the line, it's not a fuel delivery problem. Could be a partially blocked jet...

If empty, or very low, you do have a delivery problem....


Float set too high and not keeping enough fuel in carb and it runs out under load. There is a brass screen just above the float where the gas line connects to the carb... it could be blocked with crud restricting flow. The pump could be faulty or the fuel filter now clogged.

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