Carb line help. I'm so lost

[gabegrasse]

So I've been working on engines for a while now but I've never really worked on a carb. I'm fixing up my daily a 1977 c10. Used to be a farm truck from Wisconsin. And someone plugged up the carb nearly everywhere. So I'm really confused on which lines go where and where do those lines come from. the ones pictured and two in the back I've looked at tons of other forum posts and nothings really helped me. Any help would be appreciated thank you.

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[Goldie Driver]

These may help start you in the right direction - off of my '80.

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[C10MixMaster]

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Best guess

J EGR
L PCV
K EVAP canister purge
H ported vacuum
B ?

 

[gabegrasse]

Thank you guys. What about the 2 in the back?

 

[BKING33]

1 in back is usually going to brake booster.

 

[75gmck25]

The large center back port should be threaded, and have a short metal pipe connected, and that is where you run the hose to your power brake booster. I would have to look at my carburetor to see what other hose is on the back. It’s probably a small line that connects to the choke unloader diaphragm.

 

[C10MixMaster]

Thank you guys. What about the 2 in the back?

without a pic hard to say. but probably threaded port on the throttle plate brake booster and the smaller one is either for the unloader as mentioned or fresh air to the heated choke

have to realize there were a lot of variations to these carbs pics help.

your best bet is to use the reference library on this sight tons of info. Personally I downloaded ever manual and wiring diagram there. here's the page to get you started. https://www.gmsquarebody.com/threads/1973-1991-service-manuals.14499/

Just to complicate things there are 6 different vacuum diagrams for a 1977 with a 350. depends on whether it federal or comifornia heavy duty, light duty ,high altitude, a/c or non a/c.

https://www.mediafire.com/file/laz4...Chevrolet_Light_Truck_Service_Manual.pdf/file download and check page 649- 650

 

[Raider L]

And that's why I use a Holley. One carb, dozens of applications. You could take the carb on my engine and put it on a Dodge 340,360. or even a Ford 351, 352 even, other than some jet adjustments, just drive off with it. No hose guessing, hell hardly any hoses at all to begin with, or slap it on a Edlebrock and step on the gas.

 

[Taylorb27]

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Best guess

J EGR
L PCV
K EVAP canister purge
H ported vacuum
B ?

B goes to the charcoal canister. I think for bowl vapors

 

[DanMcG]

Cap everything ya can't figure out and enjoy it.
You need the brake booster, pcv and vacuum for distributor advance.