Bog/Stall on takeoff

[Speedy67]

Hi all! New here and I did search for my problem. I recently swapped out a holly 4bbl for an autolite 4100 and now the car is bogging while taking off. I barely press the petal and it immediately hesitates and if I continue to press the pedal it dies. The vehicle ran great with the holley before the swap ( fuel pressure is fine, timing is correct spark plugs have tan color, etc). The car runs great in park, no signs of hesitation and sounds smooth when revving and up to 4k rpm. I set the idle screws at 1 1/2 and 1/2 a turn for the fast idle screw, sounds the best overall in park and drive. The autolite was taken apart and dunked in a parks cleaner for two days and installed a super kit from carburetors.ca. Doesnt seem to have vacuum leaks though I will check later tonight and get an accurate reading.
*car is at 185 and choke is fully open*

 

[Speedy67]

Ok just checked her out again. She holds vacuum at 18. But I guess when I held the throttle open I didnt do it correctly. If I open it slowly I begin to here a sucking noise (such as sucking that last sip of liquid through a straw). BTW the noise is coming from the butterfly valves. If I open it slightly beyond this it will die. If I hold it past this point it lives, but shakes and that noise intensifies. If I try to richen the mixture it gets worse. My conclusion is that it needs to be cleaned again internally. So this weekend I will doing that. In the mean time if anyone has any other opinions I would appreciate it. Thanks!

 

[zookeeper]

Assuming you timing is close, anytime you have a bog, it's a lean condition. A bog off idle usually means too small of a accel pump shot, or incorrectly set accel pump linkage. The reason it runs fine in park or nuetral is there is no load on the motor, same reason vacuum secondaries don't open in park. Either you have a chunk of dirt somewhere or you need to tweak the jetting.

 

[Speedy67]

I do know that under load makes a diff. Just that I cannot turn the idle mixture screws further out than 2 turns (feels loose and I can slightly shake the screw up/down). When I got the carb from an older friend (he didnt know the condition of the carb) I didnt see that the screws were bent. Replaced the screws and applied some teflon tape (I know its like a band aid). Since you mentioned that its usually a lean problem, I did notice little fuel being sucked from the venturi's (but were plenty wet when revving the motor). With the problem with the idle mixture screws I think this carb is hopeless.

On the rebuild sheet I followed it to the specs by placing the rod on the inside and setting the float levels correctly. I replaced the fuel filter after installing the carb.

Just curious about the the two nozzles at the top of the primary venturi, they function only when the throttle is stabbed to compensate for the demand? Just figured since I noticed they only shot when revving the motor, but not during slow acceleration.

 

[zookeeper]

The idle screws are for idle quality ONLY, they do absolutely nothing once you touch the gas pedal at all. Your problem is accel pump or jetting related, so I'd look into swapping jets or trying to adjust the accel pump to get a bigger shot.