4 barrel carburetor

Hey All,

I recently bought a '71 Mach with a 351 Cleveland. The engine sounds great when idling, but just doesn't respond when I step on it. The engine doesn't knock, smoke or leak and the car has a new exhaust system and plugs now. The guy I bought it from swapped out the factory 2 barrel for a 4 barrel. Could this be hindering the engine performance?

What parts did he put in when the 2V was replaced?

First impression is that the carb probably needs to be adjusted/tuned for more than a nice idle. If it falls flat with initial WOT, then catches up eventually, obviously there are a lot of adjustments that can be made to improve performance. More information is required to advise, but finding a local 'old-school' carb guy (or gal) is a good start. Lots of knowledge here to help, but be prepared to start making small adjustments to see what happens.

Open up the distributer and make sure the weights move when you move the rotor.

Check timing and look at the plugs.

Does it have transmission kick down rod at the carb?

my first inclination would be to check the accelerator pump by looking inside the carb as you pump it or just have someone step on the gas. You should have a good strong shot of fuel. Adding a 4barrel shouldn't take away from performance just the opposite it should bring that engine to life.

How long ago was the carb swapped and did the car set for any length of time without being run? Does it have a good fuel filter? I'd also take a look at fuel pump pressure and delivery.

Accelerator pump is not squirting enough fuel into the manifold.. When the throttle is opened, the mixture is leaned out and the engine will hesitate or bog down.. Also, if the pump plunger itself is working, the fuel passage may be blocked and will not allow enough fuel to be delivered when the pump is activated.

Hey All,

I recently bought a '71 Mach with a 351 Cleveland. The engine sounds great when idling, but just doesn't respond when I step on it. The engine doesn't knock, smoke or leak and the car has a new exhaust system and plugs now. The guy I bought it from swapped out the factory 2 barrel for a 4 barrel. Could this be hindering the engine performance?

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Probably not your problem but when I bought my 72 'Q' code convertible it had a 600 cfm Holley carb on it. The car seemed pretty weak so I pulled the Holley.....HA! It had a spread bore intake and the Holley was a square bore.... The secondary throttle plates couldn't open! I eventually found a correct #'s rebuilt CJ spread bore carb and put on it. Yes, it runs MUCH better now.