Vacuum lines where do they go

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jimmy78

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Can anyone help identify what type of carb I have so I can looking up diagrams?
 

jimmy78

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In this picture it looks like you have two PCV valves, one in each valve cover. You should not have two valves, just one. The other valve cover should have a breather, or hooked to a tube with the breather in the air filter housing.

Two PCV valves could lean out the carb's fuel mixture.
I do have 2 pcvs yes.
 

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That vacuum servo on back gets manifold vacuum from the bottom rear of the carb,buy the brake booster port,it keeps the secondary air plates from opening too soon. The choke doesn't get vacuum,that's for a hot air tube on the intake manifold,if you don't have it,you can switch to electric choke or trial and error your choke setting until you find something acceptable,meaning you can still start it cold but it opens fully when warm,in actuality you don't even need a choke,it just makes cold start and cold drivabilty better. So error on the side of getting it open,not on keeping it closed. If you don't have all your original stuff,and original vacuum schematic. Vacuum advance can go straight to manifold vacuum,you could run ported,but you'll lose the advantage of having the extra timing at idle. The egr ideally should go through a thermo vacuum switch and ported vacuum. You can get away with just straight ported vacuum to egr if you have no thermo switch,but you'll have to baby it until it warms up. If you have a vacuum gauge finding vacuum is easy ported will have no vacuum at idle,but vacuum with the throttle open. Manifold vacuum will have vacuum at idle.
That's right Ricko, choke fitting is for the air tube! It's just been awhile since I've looked at an engine with a carb!
 

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How do you delete a dam message???:mad:
 
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Can anyone help identify what type of carb I have so I can looking up diagrams?
That's a Rochester Quadrajet, but all your identifying numbers are on the other side above where the throttle linkage hooks up. Get those numbers and that'll tell you what you have & the build date.
 

75gmck25

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The identifying number will be something 17080213 for a newer Quadrajet carburetor, or 7045583 for an older Quadrajet (this is rhe number from my original 1975 carb).

Your carburetor has been worked over by a brainless mechanic at some time. It’s missing pieces from the old hot air choke, missing at least one choke pulloff, and there are multiple vacuum ports open and small vacuum hoses missing. I would look for a good rebuild kit that includes a manual, and an electric choke conversion kit.
 

jimmy78

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The identifying number will be something 17080213 for a newer Quadrajet carburetor, or 7045583 for an older Quadrajet (this is rhe number from my original 1975 carb).

Your carburetor has been worked over by a brainless mechanic at some time. It’s missing pieces from the old hot air choke, missing at least one choke pulloff, and there are multiple vacuum ports open and small vacuum hoses missing. I would look for a good rebuild kit that includes a manual, and an electric choke conversion kit.
Might be easier to swap out for a new carb?

Ports were capped prior to photo and capped again after. Runs and drives fine but needs a little throttle on cold starts to stay running.
 

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Might be easier to swap out for a new carb?

Ports were capped prior to photo and capped again after. Runs and drives fine but needs a little throttle on cold starts to stay running.
I'm confused. You say the truck runs fine except for cold starts?
Changing carburetors would do what exactly? Quadrajets do have many vacuum ports but they are fairly easy to sort out.
Others here have explained the three vacuum lines that most concern you.
1) Vacuum advance goes to its matching port on the Quadrajet.
2) PVC to the large vacuum port on your Quadrajet. Mine is in front yours may be in the rear. Only one PVC valve! From the factory it was always on the drivers side.
3) Choke pull-off valve on carb goes to appropriate carburetor port.
The passenger valve cover opening should go to your air cleaner housing. I'm not entirely sure but it could also just have a breather installed. NO VACUUM connected to that opening.
 
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Geoduck

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Your choke pull off hose should go to a carburetor port very nearby on the rear.
Your choke is hard to view in those pictures. I installed a new electronic choke kit that is simple to install. You need 12 volts switched. This can be had from your wiper motor.
 

jimmy78

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Your choke pull off hose should go to a carburetor port very nearby on the rear.
Your choke is hard to view in those pictures. I installed a new electronic choke kit that is simple to install. You need 12 volts switched. This can be had from your wiper motor.
I will take a look at the back of the carb for a vacuum port that’s open. And look into electric chokes thank you.
 

Geoduck

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Jimmy, if you can give us the quadrajet series number that would be helpful too. It should be 1705XXXX, the X's specific type.
 

jimmy78

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Jimmy, if you can give us the quadrajet series number that would be helpful too. It should be 1705XXXX, the X's specific type.
I will get that number tomorrow.
 

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