After putting in a fresh motor in a 75 4 speed last weekend I am getting stalling problems when comming to a quick stop. The carb is a 4165 Holley which ran perfectly prior to switching motors. It seems as though the floats are not set right. Is it common for these carbs to require a rebuild when sitting on a shelf for a couple months. The new motor has had significant upgrades over the original, would things such as lower vacum contribute to the stalling problem. Any suggestions would be appreciated

 

recheck all your vac. line's, settings, float adjustment etc. probably something simple

 

sounds like float levels are too low, or maybe too high and flooding out the engine.

 

I remember when I first received my 4150 holley from jegs...
I disassembled it just to have a look-see.
I noticed that the secondary float was just a little lower than you would normally set it, so I "corrected" it.
I would hit the brakes, and then the rpm would drop, and the engine would die. She'd start right up, afterwards, but the next hard stop I made, sure enough, she'd stall again. Even if I put her into nuetral, she'd stall.
After lowering the float level in the secondaries, I no longer have that problem.
My best guess is, on the secondary side, that the gas is overflowing through the vent hole- I know it sounds crazy- and probably comes out of the vent tube on top of the carb. I'm probably wrong- wait for one of the carb guru's to chime in...
Another thing it might be that the primary jets are getting uncovered, causing the motor to stall. But even I don't buy that one.

My suggestion is for you to try to lower the secondary float level, and do some test runs to see if it works. It'll take 2 minutes, so what's there to lose?
Lower it a lot at first, and then gradually raise it 'till the stalling comes back.
I can't explain exactly how the high float level in the secondaries sloshes into the engine, but that's exactly what I experienced, and lowering the float level on the secondaries fixed it permanently.
Good Luck! :seeya