Stuck again....vaccum problems

[midwestls]

Alrighty, 200 87 4.3FI vaccum lines. 4 early 70's 350 vaccum ports. What do I do? I've narrowed it down pretty good but still I'm a little stuck. 1st, brake booster, got this one, to the rear base plate on the carb right? Or does it need to go directly to the intake? 2nd got the vaccum advance figured out, we're good there. 3rd the can shaped vaccum canister that also goes to te tank, does this go to the intake or the carb or does it matter? And, does the size of the vaccum hose matter? Can I make it smaller? Or should I stay with the same size as the one comeing from the tank going to the canister? Or dont I even need the canister? 4th, te ball shaped canister. It goes to the cruise control and v's before the cruise and goes over to another splitter that joins the heater vaccum. Intake or carb or does it matter? I'm a little confused here so sorry if I made a mess out of this.

 

[dan2286]

The brake booster can go to the intake or the base plate of the carb, as long as it is full manifold vacuum. I think the can shaped vacuum canister is actually a charcoal canister, it is an emissions device. I know it goes to the carb to burn the vapors, not sure where to hook it up on the carb. Use whatever fits the fittings correctly. Im not positive about the vacuum ball, but I would think it would go to manifold vacuum.

By the way, dont you have the diagram that is on the core support that shows where all the vacuum lines go?

 

[midwestls]

alright thanks. What I'm trying to do is only use what I need. Obviously brakes, lol, I want to keep my cruise and heater, I figured out my vaccum advance, and am kinda wondering what to do with the can (charcol canister) and the fuel tank vaccum (or vent? or?) Again the car was origanally a 4.3FI car and I'm still useing the in tank fuel pump. Thanks again for everyones help.

 

[midwestls]

Oh yeah, also...do I need a PCV valve??? Or can I just run breathers on both banks?

 

[85 Cutlass Brougham]

I would run a PCV valve as it does no harm and helps clean the engine. Also, there is a vacuum ball or storage cannister on most G bodies for the A/C system. There will be a one way check valve in this line ( usually gray with 3 prongs), and it is part of the system to operate the flapper doors behind the dash. Delete this, and you will not have enough vacuum to switch the ventilation controls, and be stuck on permanent defrost.

Oh, what carb are you using?

 

[dan2286]

Yes, definately run the pcv valve. Like 85 cutlass said it helps keep a clean engine. Without it, it can eventually cause oil seals to blow out. You might think it is just a bad gasket and change it, but then it will happen over and over again.

 

[midwestls]

For now I'm useing a stock early 70's vintage QuadraJet but soon it'll change

 

[85 Cutlass Brougham]

Why change it? I just swapped up from an Edelbrock 600 to a late 70's Quadrajet as I feel it is a better all around street carb.( Plus it has the right TV cable geometry, the hook up for the cruise control, accepts the stock A/C idle stop solenoid, and accepts the stock dual snorkel air filter base I have. Oh, and it has better hood clearance than a Holley or Edelbrock too, and better fuel economy when tuned right.) The only negative would be if it came from a significantly bigger or smaller engine than you have, in which case the idle feed restrictions would be sized wrong and cause it to run rich or lean. Basically, it's the same thing that happens with improperly sized emulsion bleeds in a Holley modular carb, like a 3310 on a 350.

Also, I modified mine to a 750, up from the 600 rating the late ones had by cutting down the linkage stop on the secondary air valve door with a Dremel. about 2 minutes worth of work for 150 cfm!

 

[HFX]

Why change it? I just swapped up from an Edelbrock 600 to a late 70's Quadrajet as I feel it is a better all around street carb.( Plus it has the right TV cable geometry, the hook up for the cruise control, accepts the stock A/C idle stop solenoid, and accepts the stock dual snorkel air filter base I have. Oh, and it has better hood clearance than a Holley or Edelbrock too, and better fuel economy when tuned right.) The only negative would be if it came from a significantly bigger or smaller engine than you have, in which case the idle feed restrictions would be sized wrong and cause it to run rich or lean. Basically, it's the same thing that happens with improperly sized emulsion bleeds in a Holley modular carb, like a 3310 on a 350.

Also, I modified mine to a 750, up from the 600 rating the late ones had by cutting down the linkage stop on the secondary air valve door with a Dremel. about 2 minutes worth of work for 150 cfm!

I believe their was a magazine that once tested the Quadrajet against other carbs. Not only was it the most fuel efficient if it was sized right, but it also had the best power rating from idle up to 6500 rpm.