Hi guys, My Ranchero is stalling after 5 minutes of running. 6.6l 400"m" engine. I recently carefully rebuilt the Motorcraft 2100 2 barrel carb. I found a vacuum leak between the carb and the manifold doing a smoke check so I fixed that. I am trying to put a tune on it. Engine seems to be original with very little tampering. Timing seems to be set at around 15 degrees btdc on the timing gun. If I advance the timing the idle drops and it stalls. She runs strong but shows low vacuum which continually decreases as she runs until she stalls. The exhaust seems to be pumping out of both pipes really well. The vacuum is unusually low unless I rev it up a little. I replaced all the vacuum hoses I could find. My Harbor Freight vacuum tester says "a steady drop to zero indicates a choked muffler". I am fresh out of ideas. Could I have a bad cam? Or perhaps a bad lifter? Would that even show on a compression test (which I haven't done because she was running fine prior to the carb rebuild). Any ideas would be highly appreciated. Brian
My first thought is fuel supply - carb filter was replaced, right? Float height set properly? Fuel pump? If it ran ok before, probably carb related. Disconnect the fuel line and crank the engine to verify how much fuel the pump supplies. Cam/lifter would NOT cause that problem.
That was my thought as well... its a manual pump and thise filters were cleaned. Ill check for another hidden filter by the tank though. Good idea to double check. Brian
Try spraying some carb cleaner along the intake manifold gasket line while the engine is running. If the engine speeds up, there is a gasket leak contributing to low vacuum. I've had to change out that gasket a few times with my 460 because of misses at idle speeds.
