1973 455 Vacuum Line Confusion

[mrgrayaz]

Hey guys,

Trying to untangle the spaghetti mess of vacuum lines in our new to me 1973 455.

I just replaced the existing GMC side fuel filter carburetor (for a CA emissions SBC350!) with a front snout 17056252 Toronado carb as I couldn't find a 7045254, and a now trying to undo 50 years of mods.
The PO had installed a 20lb fire extinguisher tank as a vacuum reservoir, and a Chrysler vacuum pump. Vacuum under the hood is good (and strong!). Brakes have good assist.
The PO also installed a dash vacuum gauge, which is working and very helpful. At some point a propane injection system was installed, straight to manifold.
There was a spaghetti of lines doing nothing/capped off etc on the old carb etc.
What I've Done:
Swapped carbs
I have removed the propane injection system.
I also removed the Christmas Tree.
Reran the distributer to ported vacuum off the Carb and transmission lines to manifold to see if I could solve a transmission shift concern.
I have hooked up the Cruise Control throttle rod as it now FITS with the right carb, previously abandoned. I have not road tested Cruise Control. The light does come on.

What I am not sure of:
I think I have the FRONT of the engine ok, except the diagram shows the EVAP canister coming from up the carburetor- right now its coming from the back manifold tree. Should I move it? I have the "medium" port on the Carb blocked off right now, big port to PCV, small to Distributer.
I haven't found a cruise control diagram- but it has THREE ports, one of which is coming up front, and teed in twice.
HVAC is non functional, there is a cable actuator under the passenger seat which I imagine is involved, and is running from the Cruise Control
Any help is valuable - I have a XT72425 book coming, hoping that has more info.

To Review:
Where should EVAP come from - is that rear manifold ok? or should it go the medium size ported on the Carb? If so, do I block off that rear manifold port. Where do I get plugs?
Where should Cruise Control vacuum come from and go TO?
Where should the under passenger seat cable actuator vacuum come from? (also what does it do?)
ELI5 - My head is spinning a bit - this is my first carbed engine. I have drawn arrows and labeled the lines as I see them with this overhead shot of the engine.

Anything else you see wrong is worth mentioning too (I have a new fuel line coming...)

Thank you so much!

 

[pvfjr]

Welcome to the forum! It looks like you're doing a great job so far, and heading back in the "original" direction is probably a good idea. There's a lot to learn, but you're doing well for someone with their first carbed engine.

I see you have the manual coming, and that will be a huge help. In the mean time, you can access PDF copies at the bdub.net site. Look at the assembly manual too. It's tricky to navigate at first, but it's a HUGE help for figuring out how things are supposed to be put together, and it has a TON of drawings.

I won't use the vacuum caps they produce these days. They never last more than a year or two before they start to split. I like to cut a short piece of silicone vacuum hose (about an inch) and stuff something in it like a marble, BB, steel pin, rivet, piece of plastic dowel, or whatever the size requires (anything too big to fall into the vacuum port is fine). That effectively makes a good reliable vacuum cap.

The cruise control will go to a vacuum dump valve up above your brake pedal, so that's part of the equation too. It's a good sign that your light comes on! Do you have a Mityvac? I'd highly recommend one. You can troubleshoot a lot of issues that way, and prevent a lot of future headache. I always use it to leak test unknown vacuum actuators (both cruise servo and choke pull-off), HVAC cannister, HVAC actuators, etc.

I haven't gotten my EVAP cannister hooked back up, so I'll let someone else chime in on that one.

One important tip: get rid of that rubber fuel line going to the carb. In my book, pressurized rubber fuel lines are a huge risk--especially in the engine bay. They're kind of OK as a suction line far from engine, but even then I prefer another solution. I've had an engine fire before, and I was able to put it out because I had already eliminated the rubber and switched to steel lines and a steel filter. The fire was on top of my engine, right where the fuel line was--but it did not burn or leak. It was hot enough to melt my throttle return spring and leave it all stretched out. There have been many before us who were not fortunate enough to get their engine fires extinguished. Many coaches have been lost this way (not just GMCs). I'm always seeing Corvairs burn because of rubber fuel lines too. A lot of people do it.
Edit: Doh! I just noticed you said you had a new fuel line coming. Disregard my rant!

Where should the under passenger seat cable actuator vacuum come from? (also what does it do?)

What is this? Do you have a picture?

 

[74_Coach]

Hey guys,

Trying to untangle the spaghetti mess of vacuum lines in our new to me 1973 455.

I just replaced the existing GMC side fuel filter carburetor (for a CA emissions SBC350!) with a front snout 17056252 Toronado carb as I couldn't find a 7045254, and a now trying to undo 50 years of mods.
The PO had installed a 20lb fire extinguisher tank as a vacuum reservoir, and a Chrysler vacuum pump. Vacuum under the hood is good (and strong!). Brakes have good assist.
The PO also installed a dash vacuum gauge, which is working and very helpful. At some point a propane injection system was installed, straight to manifold.
There was a spaghetti of lines doing nothing/capped off etc on the old carb etc.
What I've Done:
Swapped carbs
I have removed the propane injection system.
I also removed the Christmas Tree.
Reran the distributer to ported vacuum off the Carb and transmission lines to manifold to see if I could solve a transmission shift concern.
I have hooked up the Cruise Control throttle rod as it now FITS with the right carb, previously abandoned. I have not road tested Cruise Control. The light does come on.

What I am not sure of:
I think I have the FRONT of the engine ok, except the diagram shows the EVAP canister coming from up the carburetor- right now its coming from the back manifold tree. Should I move it? I have the "medium" port on the Carb blocked off right now, big port to PCV, small to Distributer.
I haven't found a cruise control diagram- but it has THREE ports, one of which is coming up front, and teed in twice.
HVAC is non functional, there is a cable actuator under the passenger seat which I imagine is involved, and is running from the Cruise Control
Any help is valuable - I have a XT72425 book coming, hoping that has more info.

To Review:
Where should EVAP come from - is that rear manifold ok? or should it go the medium size ported on the Carb? If so, do I block off that rear manifold port. Where do I get plugs?
Where should Cruise Control vacuum come from and go TO?
Where should the under passenger seat cable actuator vacuum come from? (also what does it do?)
ELI5 - My head is spinning a bit - this is my first carbed engine. I have drawn arrows and labeled the lines as I see them with this overhead shot of the engine.

Anything else you see wrong is worth mentioning too (I have a new fuel line coming...)

Thank you so much!

When moving the hose from the EVAP canister to the front intake port under carb, ensure that your EVAP canister isn’t full of fuel. If it is, your vapor separator at the driver side rear wheel well is inoperative causing raw fuel going directly into EVAP canister. That fuel will then get sucked into the intake and flood the engine. As me how I know that scenario!