two middle cylinders on passenger side are dead. they have good compression and my mechanic says its my carb. could it be anything else? the plugs are getting spark all the way down and plug is dry and not fouled when i check it. 1977 f250 460ci with stock carb

 

Pretty hard for a carb to shut off only two cylinders. If they aren't getting gas but the rest are,, then I would suggest pulling the valve cover and checking the springs and valves. Make sure all are freely moving. Could also be the lifters on those cylinders. The carb is Not the problem. Also check for any kind of seal/gasket leaks at the mating surface of the head/block and intake/head.

 

Doesn't sound like the carb. You could have problems with the exhaust valves, or maybe cross fire on the plug wires. Make sure the wires are on the correct cyinders.

 

Good point on the wires, bear. Also make sure the insulation is intact on those wires. They could be grounding out when trying to ignite the chamber.

 

everything under the valve cover looks to be working fine. my mechanic put all new intake gaskets on and them he put his holley 650 on it. it ran like a brand new truck them he put mine back on and it was a dog. when i cover the carb it does not die when i spray carb cleaner or wd forty around the idle does not pick up could it be the vaccum lines routed wrong

 

sounds like maybe a flat cam, are you sure the push rods are pushing the rockers high enough? oldcarnut, 77supercab

 

the rockers and everyting are working fine when you put a holley on it it runs like brand new the plug wires are new and sparking all the way to the cylinder could the vaccum be routed wrong when i cover the arb it does not die and ive sprayed everywhere trying to find a leak and i cant seem to find one i appriciate the help

 

That would not explain the carb change and it works fine. I would change the fuel filter, then take the carb apart and clean it, see if it gets better.