top of third losses power?

[fly4spd]

the car has the stock 4 v carburetor, rebuilt last year and is stock other than the exhaust listed below. when i hit 4k the car just seems to not get any power. I'm going to go get some carburetor cleaner in the morning and i hope that will fix the problem but what else could it be? A new intake manifold and carb are coming soon so if it needs to be replaced i'll just have to wait until i do the upgraded stuff.
thanks
-aj

 

[NeVeRLiFt]

You could be running out of fuel. What gear does the car have and is it a auto or stick?

Check the timing and your vacuum advance, make sure its all in by 3200-3400 rpm. When was the plugs and wires changed and how do they look?

 

[FiveO]

make sure the clutch isn't slipping...are you sure its only 3rd? what about 4th and 5th?