Edelbrock Air/Fuel Screw Not Working!!!

[savatreatabvr]

I have an Edelbrock 1407 on my mid 70's C/20 454. The drivers side mixture screw works but the passenger side doesn't. I can screw it in all the way and nothing! I also hear a high pitched vacuum leak while driving at steady speeds, when I let off the gas it stops until I give it more gas. I've played with the adapter plate (Edelbrock 2696) and countless gaskets with no help. I've sprayed water around the intake manifold and carb and no leak! Could the throttle shaft be lose enough to create such a loud vacuum leak? I've checked everything else, what am I missing?

[meatwagon83]

Did you check the hose to the brake booster? Also the little valve at the booster

[Dead Parrot]

Suspect every vacuum line and what they connect to. Vacuum advance on the distributor, line to the tranny if you have a TH350, line to the vacuum pot for the AC/heater stuff, power brake as mentioned, any and all emissions stuff with vacuum connections, PVC hose and valve. Charcoal canister if so equipped.

[motornut]

make sure the metal tubes on the carb are tight sometimes they pull out a touch,pulling hoses,a slight tap may reseat some

[geezer#99]

Hook your vac advance to manifold vacuum, the idle will speed up, then turn your idle back down and your mixture screws will both work and the whistle will go away.

[savatreatabvr]

Originally Posted by geezer#99

Hook your vac advance to manifold vacuum, the idle will speed up, then turn your idle back down and your mixture screws will both work and the whistle will go away.

The vacuum advance is already on manifold vacuum. I've been working on my own cars since I was 15 years old, I'm 47 now so I've tried everything I can possibly think of, numerous times. The only thing left I think it would be is the throttle shafts leaking since Edelbrock does not use bushings. I'm seriously thinking about buying another carb whether it be an Edelbrock or Quadrajet, I'm not a Holley fan and start eliminating possible causes by replacing parts. Don't know what else to do!

[geezer#99]

Check that both throttle plates are set in the bore the same. The one where the mixture screw won't adjust could be bent a bit exposing the transition slot completely. I had a quadrajet that did that.

[INSIDIOUS '86]

Wiggle the throte shaft. It shouldn't wiggle to much. How you fix a quadra jet is throw it on the ground real hard kick it then put it in the trash. Then bolt on an edelbrock. How you fix an edelbrock is throw it on the ground and bolt on a holley. True story back in the day haha.

If you do have a vacuum leak your idle slots may be covered way to much to respond

Another idea is if your initial isn't high enough or vacuum advance stuck or failing the idle screw is to far in and the transition slots are over exposed.

Or it's just another edelbrock that doesn't tune. In which case if it isn't causing a issue then just leave it.

[meatwagon83]

there is nothing wrong with a quadrajet

[savatreatabvr]

I agree! I'm a Quadrajet fan. The only reason I have an Edelbrock 1407 is I got a screaming deal on Craigslist. Ok, the only time I hear the vacuum leak is while I'm driving so the leak occurs only during higher RPM's and under a load. I meant that's only time I hear it so how do I check that, crawl under the hood and have a friend drive my truck? I'm at my WIT'S end!

[PAWS 72]

I 'm havin a whistlin problem also with mine. I have checked everything. 6-8 mpg's aint cuttin it. Didnt know if swappin sides with vacumm could be done.