Vacuum leak at choke?

[65GTO]

I have a 17056274 Quadrajet on my 65 GTO. Its apparantley an 800 CFM. I am wanting to replace it but cant find a good core locally, so for now I am trying to fix it. With the idle screw backed out all the way, I cant get the car to idle below about 800 RPM. I believe there is a Vacuum leak somewhere,and when I pulled apart the choke cover, I could hear a hissing sound which appears to be the source of my leak. The car has a 69 400 in it,so I would like to remove the existing choke and go to a divorced style,not sure if this is even possible. Anyways,can anyone tell me what/why I would be hearing that hissing when the black choke cover is removed from the housing? What would I need to do to remedy the issue. And secondly,based on the numbers provided,is this a decent base carburetor to start with?

thanks!

Brian

[429bbf]

wecome aboard 65 ill answer what i can . you need to screw the idle screws in to slow it down. they control the fuel air mix.the hissing sound thats coming threw you choke can be plugged . if thats what you want to do .its purpose is to pull hot air from the manifold threw the choke housing and warm up the coil.what i found best is to just covert to electric. its plum easy. just remember to leave the gasket out behind the choke coil because it has to ground through the housing.fwiw

[65GTO]

So with a little tinkering and some help from the forums I figured it out. Turns out the secondary linkage was binding and not allowing the throttle plates to close fully. A little tweaking and it idles nicely at 700 RPM.

I have the timng set at 12 Initial,and have about 18 degrees of Vacuum advance. Dwell is solid at 30. The car still has an off idle stumble,and the accelerator pump seems to be pumping out lots of fuel,just wondering where I should be looking to solve that issue.

Also wondering if there is a divorce choke kit available for this carb that would make it would with my stock 69 intake? based on the fact that its 800CFM,and the numbers in my initial post,is this a carb worth working with? Ideally I would like an early one that would work with an early air cleaner anyways,but its running much better now.

Can anybody walk me through the procedure once more for dialing in the idle mixture screws? The way I do it now is screws out to maximun RPM, then is until I see a 50 RPM drop,then out 1 and 1/4 turn. make sense?

Thanks again!

[omaha]

 I do not think that a divorced choke can be mede to work on that carb, however I am not 100% sure. It would be way,waay more easier to buy the electric choke conversion and go that route. Just remove the choke and rod from your manifold and stash it away somewhere. If you find the original carb you can always go back to the divorced choke set-up. The current carb you have is called a M4MC this means it came with a  integrated choke housing ON the carb. It used hot air from the manifold (routed through a small steel line) to the choke housing. This is easily changed to the electric choke, jus replace the choke coil and plug the hole in the carb where it draws the vacuum. All you need is a 12 volt KEY-ON power source. (wiper motor etc.)
   As far as the setting of the idle, it is easier done using a vacuum gauge (think SEARS) but you can get quite close by doing it by ear. Just screw out the idle needles about 4 turns from LIGHTLY seated (maybe more). Start up the engine and start to turn  the screws in about 1/2 turn each (counting each time so you dint forget)keep turning (again 1/2 at a time) when the engine starts to run rough (from lack of fuel) that is when you will turn the screws back out until the engine stabilizes again. (remember same amount each 1/2 turn) At that point you may want to screw tham out another 1/2 turn. make sure both screws are in the same position (equal amount of turns).  This is the way I do it and yes the rpms will drop when you get to the point when the engine starts starving for fuel. I just go from the sound of the engine and experience. I don't know if it is exactly 50 rpms but I go with the sound, not the rpms gauge. You will get the hang of it and you will hear the difference.  A vacuum gauge and a RPM gauge will make it more accurate to do this.
Remember, GTO stands for "Get the Tools Out." LOL good luck!!

[Cliff Ruggles]

The 17056274 is an excellent carburetor, I'd stick with it.  If you haven't done so already, I'd install one of our kits, and convert it to electric choke.  Wouldn't hurt either to retune for the application and this new fuel, the engine will respond well to some additional fuel.  We stock everything for that part number, and can send the correct tuning components and E-choke conversion with the kit.....Cliff