Edelbrock carb gets stuck in wide open throttle at start up?

[CouldveBoughtaCamry]

Just picked up a shiny edelbrock 600CFM carb that is less than 4 months old to replace a junkyard quadrajet. The linkages to my throttle and return spring work with the spring pulling the linkage to the furthermost position at rest. If you turn the key the engine takes 3-4 seconds to start before revving at an incredibly high RPM almost as if open throttle. Mixture and idle speed screws seem to do nothing are there any edelbrock experts out there? No one seemed to have a similar problem.

What baffles me even more as I can confirm that the throttle plates are closed when I look down the carb. Any help is appreciated.

[CouldveBoughtaCamry]

Linkage shots-obviously the throttle cable and spring are not in permanent spots, was disconnected before the picture.

[67C10Step]

Vacuum leak? Have you tried spraying carb cleaner around the base of the carb when running to see if there is leak at the base plate?

Might be a shot in the dark but that is where I would start.

[CouldveBoughtaCamry]

Originally Posted by 67C10Step

Vacuum leak? Have you tried spraying carb cleaner around the base of the carb when running to see if there is leak at the base plate?

Might be a shot in the dark but that is where I would start.

Engine runs at such high RPM I never tried to keep it running but I doubt it is a vacuum leak unless there is a hole the size of my fist in my intake, it just seems to rev way too high.

EDIT: She starts even with a rag over the carb, will update.

Ok, so with a towel draped over the carb she still starts and revs insanely high, just switched over the gaskets to see if that did anything but no dice.

[68 P.O.S.]

Sounds like the high idle, or fast idle, screw needs to be adjusted.

[Dead Parrot]

What manifold? Some require an adapter plate to seal, others don't. IIRC, the places to check are the sides of the carb. Doesn't take much of a slit of miss-match to cause a problem.

2nd check the fast idle screw. IIRC - it is the one at the bottom of the linkage in your first pic. Open the throttle to adjust.

You can download the owners manual from the Edlebrock site.

[68 P.O.S.]

If you're not aware, the high idle/fast idle is part of the choke system. As the engine warms up, the fast idle increases in proportion to it. So when the engine is cold, the fast idle keeps the rpms around 800 so as not to stall (not sure of the actual rpm off the top of my head). When the engine is fully warmed up, the fast idle should be at 1500 rpm (the GM recommended speed). The fast idle screw itself is located further behind and below the curb idle screw. To adjust it, push the throttle linkage to full throttle with your hand and hold it there. Look below it and the screw will be visible now. You'll have to play with it a few times to get it right, I adjust mine by letting the engine warm up completely with the choke on, then I adjust the screw. I got mine to 1400 rpm and called it good.

[PGSigns]

I am almost willing to bet that the carb is not a quadrajet replacement and it has a big vacuum leak. The Edelbrocks have the holes to match the quadrajet pattern but that's about it. I think your going to have to put one of these under it to make it work. After that you will be able to get the choke and fast idle set.
Jimmy
https://www.summitracing.com/parts/spe-5765

[68 P.O.S.]

I re-read your 1st post and you mention that the idle mixture screws and idle speed screw do not respond. The reason for this is because of the higher rpm its running at. As the two names suggest, they only work at idle. Right now you should be able start it, and once it revs up as usual, tap the gas pedal once to disengage the choke. This will drop the rpms back down to whatever the idle speed screw is currently set at and then you can adjust the idle mixture and idle speed screws from there.

As already asked, which intake manifold are you running? I’m assuming spread bore since you said you pulled a quadrajet off of it. It really doesn’t matter if its spread bore (quadrajet) vs. square bore (Edelbrock, Holley, etc.) as Edelbrock carbs are designed to fit on either type of intake. However, an observation I made from your pics, you have the carb straight on the intake (with the little paper gasket). Regardless of intake type, you will need a heat insulating gasket between the carb and intake. Edelbrock carbs are notorious for percolating fuel, which causes hard starting issues. To cure this, you’re gonna need a square bore adapter plate (Edelbrock 2732) with a heat insulating gasket (Edelbrock 9266) on top of it, then your carb. In addition, Edelbrock carbs are fuel pressure sensitive and will flood at pressures higher than 6psi. Edelbrock recommends a fuel pressure regulator set to 5.5 psi, or their Performer RPM fuel pump which puts out 6 psi (any fuel pump that puts out 6psi max will do). You will also need to double check and set the float levels to Edelbrock specs as well because this will also cause flooding.

What is your timing set at? Which type of distributor do you have?

[paul mora]

I can’t tell exactly but something looks wrong with your spring cable attachment. You should check it out before you start it by working the the throttle cable there should be a screw There thatyou can fine tune your rpm that looks wrong

[68 P.O.S.]

Originally Posted by paul mora

I can’t tell exactly but something looks wrong with your spring cable attachment. You should check it out before you start it by working the the throttle cable there should be a screw There thatyou can fine tune your rpm that looks wrong

He knows, he mentioned that in post #2

[sweetk30]

were your return spring is hooked does it hit and catch the stock gm factory air cleaner base ?

had this happen to me years ago . 1" spacer fixed the problem if i recall .

and what is up with the throttle cable pin setup ? ? ? totally wrong setup for sure .

[61K10]

spread bore intake, as you said it has a big hole in it. edie carbs do not fit all spread/b manifolds without this plate.