I just put a factory remanufactured edelbrock 1406 on my 79 f 150 w/ 400. It has a 268h comp cam, dual exhaust, edelbrock performer manifold. The 1406 is replacing a 750 holley. I do have a 4 hole 1 inch spacer that was put on it when it still had the 750 holley. It was my first time putting a carb on right out of the box and it went pretty good except for one thing. I can hear air "sucking in" i guess you could say. I put the plug in the rear of the carb and it is tight. At first it sounded like it was coming from the rear and it was not really strong it was barely noticable. I have sprayed carb cleaner all over the place and the motor's idle did not seem to pick up at all. I put a vacuum gauge on the manifold vac on the vacuum tree @ the back of the manifold and the needle jumps. It has an older aftermarket open air filter element on it. I dont think it is a vacuum leak and when i take the lid of the air cleaner the "air sucking" sound gets much stronger. Anyone have any idea on what the problem is? I have the back plug in and the cap on the manifold port on the vacuum. Did i need to put teflon tape on the threads of the back plug? I would assume not but ya never know. The truck runs fine, actually better than the 750 cuz it was loading up badly from too much fuel. Also is it ok to use a rubber 5/16 fuel hose instead of a 3/8 rubber fuel hose? thanks for the help guys

 

Edelbrocks are usually noisier at an idle than a Holley. My 750 is the same way on my 460. Just adjust the mixture screws until you get the highest vacuum and go from there. Also the vacuum advance hooks up to the left port on the front of the carb.
I do use teflon sealer on the pipe theads on the rear plug.

 

i have it hooked up to the timed port on the passenger side already. The needle jumps quite a bit but i will mess with the idle screws later. Maybe i will put some teflon tape on the plug tonight.