440 with holley - popping noise.

[Peter]

Hi all.
Question. When I am at idle and punch the gas hard, I get a pop up the carb. even when at operating temperature.

Now, I checked the spark plug wire firing order to ensure it is firing in sequence, changed plugs. I am at 16 degrees BTDC in idle and aobut 38 all in at 3000 rmp.
The pump nozzle on the double pumper holley 750 is 35 for both front and back.
I checked for vacuum leaks and there seems to be none. Checked with brake cleaner.
It idles at 950 in Park and 750 in drive.

Now, I know that this popping up the carb is a lean condition. But at 35 pump nozzle tip, should it not be getting enough fuel?

Thank you all.

 

[coloradodave]

With the motor OFF and the air cleaner removed, make sure that ANY movement of the throttle moves the accelerator pump arm. If there is a delay you can adjust the lever to remove any play. You can also play with the pump cam position to provide an instant shot. Next, again, with the motor OFF, look down the carburetor throats and work the throttle. Do you see two nice strong streams of fuel squirting in on the primaries and the secondaries? If not, maybe the pump shooters are partially clogged. Be sure and check the float levels as well.

 

[Photon440]

Yes, check out the above suggestions. Also, without changing nozzle tips, pump shot delivery can be altered by changing the cam that moves the lever. This link from Holley shows an assortment of several cams in a kit.
http://www.holley.com/20-12.asp
If you have a manual choke, try punching the throttle with the choke partly engaged for testing. It should let you know if it is indeed a lean condition.

You indicated having an automatic tranmission, which could benefit from a vacuum secondary carb.

-=Photon440=-

 

[shag766]

this way out there but, possible something in the valve train not right, maybe.