carb question on m4me quadrajet

[Jeramy]

I have been running my truck on ported vacuum(passenger front corner) and after much reading and talking to local builders went to switch it to manifold vacuum(front drivers side) only to find that it also has no vacuum at idle also.

Carb is m4me quadrjet number 17084290. stock carb for 81 c10 with 350/auto.
Any suggestion or should i return it under warranty and try with another one?

any and all help appreciated and thank you in advance.

[geezer#99]

Might be you have the wrong carb gasket and it's covering the port in the base.
Have you checked the other ports?
You might need a vacuum tree behind the carb.
https://www.paragoncorvette.com/c-22...aspx?pagenum=1

[Jeramy]

i used gasket recommended for application by felpro but still a possibility. i do get strong vacuum from it off idle just none at idle.

[enaberif]

Do manifold vacuum off the port behind the carb on the intake manifold. you may need to put a nipple in its spot.

[Jeramy]

will try that this weekend