Carburetor Vacuum Lines

[dzwestwindsor]

Hi guys,

I have a 1971 C20 with a 350 and Quadrajet carb.

Take a look at pictures of my carb:
front view: http://imageshack.us/f/407/cdiv.jpg/
diagonal side view: http://imageshack.us/f/545/3d7u.jpg/

I have two concerns:

1. In the front of the carb, what is that vacuum port for? What is it supposed to be connected to? If I put my finger on it, I feel a pretty good suction. I feel like it's missing a hose to somewhere.

2. In that diagonal side view image, is that hose supposed to be routed back up to the air cleaner? When I got the truck it was only connected on the carb end so I guessed that the other end goes up to the cleaner, but I'm not sure. Is it the hose that keeps the float bowl fuel pressure constant?

It'll be great if someone could point out what those two vacuum ports are for.

Thanks in advance,
David

[Drewski23]

Pcv on the valve cover?


Actually on my truck ive got 3 spots in the front for hoses...vac advance, fuel, then the third is plugged. So yes i think its for the factory air assembly

Mine has an edelbrock carb but im sure they have the same hook ups

[mmiddle]

Wow, this is really early Q-jet.
The front one is (should) Venturi vacuum. Cap it off.
The rear one, the picture is not very clear, should be manafold vacuum and it should be for the PCV system.
This carb, I think is an early-mid 1960 model.

Do us a favor and pull the air cleaner and take better pictures. I'm wondering if this is an early square bore Q-jet. 1959-1965 era.

[dzwestwindsor]

For question #2, I was referring to the thinner hose that comes out of the carb near the choke and goes back up to the air cleaner. (I know that the big hose back there is the PCV, but what about this thin one?) Not sure if it's actually supposed to go back up to the air cleaner.

[mmiddle]

A: Venturi vacuum. Cap Off
B: PCV system Vacuum
C: Thermostatic carb heat vacuum source. If you are still using the system keep this. If not... Cap Off
D: ????? Cap Off

[hoovers71]

the small line coming off near the choke goes up to the air cleaner.

[asolde]

Here you go

[dzwestwindsor]

Thanks everyone for your help. I'm going to get some plugs right now.

And mmiddle, here is the carb without the cleaner over it... do you know anything about it?







-David

[mmiddle]

I was wrong...or hoping I was right It is just a regular Q-jet. Those first pics looked weird.

[mikeshome]

I know it needs a good cleaning.lol