The four barrel does not kick in, What can I do?

There may not be anything wrong. On a two-injector throttle body, the second injector acts similarly to a four barrel carburetor. On a four barrel, only two barrels supply fuel until you kick the accelerator pedal down hard for quick power for passing as such. At idle or normal cruise the second injector in non-operable. Only when you kick the pedal down (passing gear in old school terms), does the second injector activate.

Catalytic con.clog.

As long as it is a carbureted engine , simply change intakes and install your four barrel . Yes it is computerized , but will not interfere with carb swap .

On most models, the secondary barrels would only work if the primary are in wide open position, and even then the range of opening is small.
The engine should run past 3000 RPM on just the front barrels, so you may have something else going on.

1)iginition timing is incorrect
2) distributor advance is not operating properly
3) Varios defects in your engine ignition system
4) fuel pump defective.
5) aire cleaner defective.
6) excessive back pressure in your car exhust system
7) engine positive crankcase vestilaltion system is clogged.
God bless you

Sounds like you plunger is not working rt. may need a carb kit. good luck.Could try some carb spray in your carb.. or another possability is you got some bad gas somewhere, .

It depend on how fast your going when you kick in four wheel drive. You should be doing no more than 20 mph for it to kick in.

Sounds like you have a vacuum leak,around your
new manifold or carburetor. No the timing will not be different between a two barrel or a four barrel carburetor.

Put a 4 barrel intake manifold on it.

http://holley.com/data/Products/Technical/199R9881.pdf
This should help you