Have no idea what these tubes are!

ceejay · Oct 2, 2020

I've been trying for about 6 months now to try to get my 81 daily driver ready, and I am still fixing odds and ends from the previous owner really butchering it. These 2 tubes, (among a lot of random things) were just sitting in the engine bay, around the carb to be exact. Can anybody tell me what they are and where they go? It runs and drives without them. The one tube is just sitting there, disconnected from everything. The other tube is plugged into whatever that is behind the engine.

Thanks.

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louu · Oct 2, 2020

The one off the distrubiter is the vacuum advance for advancing the timing at higher RPM's but you probably already know that.

Bextreme04 · Oct 2, 2020

Its impossible to tell what those go to from a picture like that. The last picture is the vacuum advance for the distributor. It should be connected to manifold vacuum on the carburetor.

Bextreme04 · Oct 2, 2020

louu said:
The one off the distrubiter is the vacuum advance for advancing the timing at higher RPM's but you probably already know that.

That's backwards.. vacuum advance goes to manifold vacuum and advances timing at idle and low load conditions(like highway cruising) for better fuel economy. Mechanical advance increases timing with RPM and happens automatically with weights and springs internal to the distributor.

82sbshortbed · Oct 2, 2020

Don't you disconnect it when setting timing? I can't remember. I'll be swapping distributors this weekend. I've ran the advace hose to the bottom port on carb too. Is that wrong too?

louu · Oct 2, 2020

Bextreme04 said:
That's backwards.. vacuum advance goes to manifold vacuum and advances timing at idle and low load conditions(like highway cruising) for better fuel economy. Mechanical advance increases timing with RPM and happens automatically with weights and springs internal to the distributor.

Thanks bud, learn something new every day from this forum.

TubeTruck · Oct 2, 2020

That y-ish Tee comes off the side of the carb. There should be a little piece on the carb that goes into the Tee, one end of the tee goes to the bottom of the air cleaner and the other end goes to a thermo switch around the thermostat. The distributor was also originally plumbed into this switch as well as another port on the carb.

I know someone on here has a pic handy but I can't find mine atm.

Edit: found it

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Bextreme04 · Oct 2, 2020

82sbshortbed said:
Don't you disconnect it when setting timing? I can't remember. I'll be swapping distributors this weekend. I've ran the advace hose to the bottom port on carb too. Is that wrong too?

Yes, it needs to be disconnected and the port plugged on the carburetor when setting base timing, idle speed, and idle mixture. It needs to go to manifold vacuum. This will have a suction at idle, ported vacuum will not have suction at idle and will get increased vacuum as the throttle body is opened. If you have base timing set correctly and the vacuum advance set up to manifold vacuum, you will have a higher advance under lower loads which will allow the engine to get better mileage without detonating. If you connect it to ported vacuum, you will get no benefit at cruise or idle and will also potentially get detonation at high load.

ceejay · Oct 2, 2020

Well thanks guys. It came with a Edelbrock 1405 carb, so I'll have to do some looking later when I go back out there and see where they go. PO did lot's of macgyvering to this engine.

ceejay · Oct 2, 2020

I got the one from the dist hooked correctly I believe (left hose). Other hose (white tee) I still don't understand. I guess one part of it goes to the factory air cleaner port I uploaded? Also, I want to say it was hanging off of this little port going into the engine when I got the truck. Sorry guys, trying to learn new things everyday.

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Bextreme04 · Oct 2, 2020

So, the green and orange thing are the control valves. They are TVS's(thermostatic control valves) and will open when warm. They are used as emissions controls to keep the vacuum advance and evap from activating on a cold engine. They are expensive and fail regularly, so they are often bypassed. The left port on your edelbrock is ported vacuum. The right is manifold vacuum. The larger middle one is for PCV and should be connected to the PCV valve on the valve cover. My truck doesn't have an Evap canister. I have both TVS's bypassed and only have manifold vacuum direct from the carburetor to the distributor. I also don't have a factory air cleaner though, so no diverter valve.

ceejay · Oct 2, 2020

Bextreme04 said:
So, the green and orange thing are the control valves. They are TVS's(thermostatic control valves) and will open when warm. They are used as emissions controls to keep the vacuum advance and evap from activating on a cold engine. They are expensive and fail regularly, so they are often bypassed. The left port on your edelbrock is ported vacuum. The right is manifold vacuum. The larger middle one is for PCV and should be connected to the PCV valve on the valve cover. My truck doesn't have an Evap canister. I have both TVS's bypassed and only have manifold vacuum direct from the carburetor to the distributor. I also don't have a factory air cleaner though, so no diverter valve.

So I feel as if I can leave the green and orange things for now bypassed (although it seems they're bypassed by screws, might find a way to make it look better later). The white tee I feel as if I can leave off as well? I see where it can be hooked up to air filter, but not my edelbrock carb?

Bextreme04 · Oct 2, 2020

ceejay said:
So I feel as if I can leave the green and orange things for now bypassed (although it seems they're bypassed by screws, might find a way to make it look better later). The white tee I feel as if I can leave off as well? I see where it can be hooked up to air filter, but not my edelbrock carb?

You can just unhook everything from the valves. They would normally just turn on the connection between the carb and the other units based on temp. If you just leave everything unhooked and connect straight from the carb to the components, you will bypass the valves and the valves will just act as coolant plugs.

eskimomann209 · Oct 5, 2020

To elaborate ( might not be needed)
The hoses connected to the green valve with the nails suck in em. Pull the nails out, remove the hoses. They create NO vacuum so there’s no need for caps/ hoses.
Also some of your hoses look well past expiration date. Soft collapsing hoses or weather checked hoses create undue problems. Replace them.

trukman1 · Oct 5, 2020

Boy do I feel silly! When I saw the first picture I thought, "Why, that's the line for your windshield washers." (Because of the angle.) Duh!

Have no idea what these tubes are!

ceejay

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82sbshortbed

Fuckemall!!

louu

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TubeTruck

I'm from Boston. Deal with it.

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