Vacuum Lines and Quadrajet

[Chief Brody]

I need some help with the vacuum line hookup....can somebody help me with these ports?

not sure but here is what I have so far:


1. to charcoal cannister (is a bowl vent)
2. distributor vacuum advance
3.
4. PCV Valve
5.
6.
7.
8.
9.
10.
11.
12.
13.
14. Brake booster (needs fitting)

 

[dyeager535]

I figured someone here would remember all that stuff. I certainly don't.

As I recall, #14 is for your brake booster though.

#8 I believe is a clean air feed, for something like a hot air choke?

Sorry I can't help more, I haven't dealt with these in years.

 

[Chief Brody]

bmp

 

[80' 427]

Where is your emissions sticker?

 

[80' 427]

14 is for the brake booster and needs a fitting. 4 is for the pcv, 1 is a bowl vent and goes to the carcoal canister,

 

[Chief Brody]

14 is for the brake booster and needs a fitting. 4 is for the pcv, 1 is a bowl vent and goes to the carcoal canister,

charcoal cannister on the firewall or on the radiator core support? There is a round ball shaped thing with a vacuum line that I haven't put back on the firewall yet.

 

[80' 427]

6" or so plastic cylinder on the radiator support.

 

[samsterman99]

11,12,13,14 are all manifold vaccum, so they can be used for brake booster, AC controls, MAP sensor, Vacuum gauge, ect.
Anything that is below the carb butterflies is actually going to be manifold vaccum, so im sure there are more of those ports on the carb that can be used for a vacuum refrence to your dizzy.

As said above, you have your PCV valve, charcoal emission canister, and your ported vacuum already found. so I would hook up the rest of the items that require manifold vac. Plug the others and give it a test!

 

[Chief Brody]

where do I get a fitting for #14 for the brake booster...as I recall that hose is pretty big.

 

[samsterman99]

if I remember correctly it was a flared compression fitting, not sure on the size. but I am sure your local hardware store has adapters to make it a barb fitting on the end.

 

[80' 427]

Should be a piece of tubing.

 

[82355]

I've used an air hose male quick couple before . . . . .

Martin

 

[mdm365]

where do I get a fitting for #14 for the brake booster...as I recall that hose is pretty big.[/quote

Be very careful that you don't over tighten this fitting it will crack the base plate. The fitting has tapered threads. I used # 13 for my brake booster.

Mike

 

[dyeager535]

charcoal cannister on the firewall or on the radiator core support? There is a round ball shaped thing with a vacuum line that I haven't put back on the firewall yet.

Round ball shaped thing is to run any vacuum accessories in case engine vacuum is low. Not a bad idea to keep IMO, although if your engine has strong vacuum, not a whole lot of reason to keep it, UNLESS you have AC. Cruise control is the only other item I can think of that might need that vacuum reservoir.

As you thought the cannister is on the core support. One of the few emissions devices I personally don't mind.

 

[mrcaruso]

My Quad is a 1974 Chev with 2 vacuum ports on the front of the float bowl with a vacuum choke. Both are manifold vacuum which puts in all the advance in the distributor when hooked up. I tried the vacuum line that comes out the choke setup but not luck there either. Any ideas on what I could be doing wrong here?

 

[dyeager535]

Are you trying to find a ported vacuum source? Do you need one for emissions testing/inspection?

Pulling advance at idle doesn't hurt performance, up around 20* it will idle excellent. Being manifold vacuum, the advance will drop as you hit the throttle (when driving, not parked and increasing throttle). Somewhere on the net is an article by an old GM engineer that makes it pretty clear that ported vacuum advance was designed solely for emissions.

As tailored as each carb was to each application, it's possible that going with manifold vacuum will cause issues if that was not how it was setup, but with a bare engine, manifold vacuum is really what you want. Real point of contention, but it shouldn't be...vacuum drops as load and throttle increases so mechanical advance takes over, and more idle advance makes the engine idle smoother.

 

[mrcaruso]

The HEI dist. I'm using has adjustable advance built in, which set at approx. 19 degrees the least amount. When I hook up the vacuum to it, the entire 19 degrees seems to come in which runs the rpm up about 1000. Since this is a 1974 Chev carb, I don't see where an emission port would be or what it was used for back then. I have a TPI on my 56 Chev, but I chose the Quad to use on an aluminum manifold I had strictly for the car cruises and the old look.

 

[dyeager535]

So any reason you can't drop the hot idle back down via the throttle stop?

After I started getting into EFI and realized that you could (and should if possible) run a bunch of advance at idle, I thought it would be interesting to take a carbed vehicle, and set it up so that idle advance through vacuum was around 20*.

The only limitations I believe exist are how fast the advance canister bleeds off vacuum (which can be changed) and that you end up with a low mechanical advance number for easy starts, and still get advance where it should be at higher RPM's while loaded.

 

[mrcaruso]

When this problem began, I used the idle adjustment and it was completely off the stop. Then when the vacuum line was removed the motor would die. I could live with this if it only bumped the idle 200 or
300 rpm.

 

[dyeager535]

Are you able to get adjustment out of the idle mixture screws? IIRC, if you run out of adjustment with the throttle stop, you are supposed to adjust the mix screws. If the throttle plates are closed at idle when the mix screw is all the way out, need to choke it with the mix screws.

Now you say "when this problem began" which indicates something changed, but it sounds like you just installed this carb?