Hey everyone, haven't been on here for awhile, got lots of projects going on and one of them is getting my dads 70 delta 88 royale on the road again. Its got a 455 with a 4 brrl quadrajet conversion on it. I got the quadrajet off a chevy 350 motor for free but i put bigger metering rods in it to give the motor more fuel when needed. 1st issue, after driving it the engine makes a hiss noise after i turn it off, almost like it is sucking in air and the engine runs for maybe 1 sec after key is off. it only does it every now and then but i know this isn't normal. 2nd issue, there is hesitation going from dead stop, almost as if the carb cuts out for a brief moment, also sounds like its sucking in air. I dialed the idle mixture screws to 2 turns out, am i running too lean? How would i properly adjust the carb since it was off a 350ci? i read an article about weak manifold vacuum causing the carb to "load up", is this what is going on? 3rd issue, once i am stopped at a light the brake pedal begins to fade, to the point where it touches the floor. When i am moving the brakes work great and stops really well but at idle it slowly goes to the floor but the brakes still hold the car at a stop. Is this vacuum leak, air in the lines, carb related? I know its a lot of issues but i'm not sure what to do? Thanks for all your replies.

 

The hiss is probably a vacuum leak and you have a vacuum canister to accumulate vacuum, also your power brake booster or line may be leaking. I'd fix the vacuum leak and then see how she runs.

What is your timing set to, and what type of ignition are you running. All carbs basically adjust the same way for idle. Use a tach or vacuum gauge, and adjust the A/F mixtures screws for highest rpm or vacuum, then readjust idle speed, and repeat.

 

Thanks Oldcutlass, yea there is a vacuum canister in the engine bay but idk if any lines are hooked up to it so that could be it right there. Its set at stock ignition with stock distributor. Bought new cap, rotor, and points. Once i track the vacuum leaks i will move over and redo all the ignition and carb tuning. However i can't find a vacuum diagram for my dads car, any help on that?

 

"i put bigger metering rods in it to give the motor more fuel when needed."
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I was under the impression that the metering rods blocked part of the hole thru which the fuel flows. Therefore, a larger metering rod will block more of the orifice and therefore LESS fuel will get thru.

 

ohh yea sorry got that reversed, thanks for looking out.