Anyone know what these switches and vacuum lines do?

[AuroraGirl]

My 1980 gmc k2500 has a 350 that must have came out of a car at some point since it has a 2 barrel on it. Im going to be changing the intake manifold and carburetor to edelbrocks. However, I would like to know what a few things which are resting are on my manifold so I can delete them or hook them up if they are needed for something. All the old emissions equipment will go away as well, since none of them work anyway and just clutter the top of the engine.

Everything is color coded that im curious about so that the different angles you can see the same things.

When I put my new carb on, I will run a new line to the vacuum advance to the timed port, since it seems like HEI likes timed vacuum or something

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[Charlie]

 

[MrMarty51]

Green is the choke pull off, after engine starts, it pulls open the choke to keep the carb from loading up the cylinders.
Light blue and red is thermal vacuum switches that controls vacuum to various items during various temps.
Dark blue, I`m not real sure, unless it would be to filter any oil or fuel from entering the vacuum brake booster.
Welcome to the GM square body AG.

 

[1987 GMC Jimmy]

Dark blue is the brake booster filter.

 

[C10MixMaster]

My 1980 gmc k2500 has a 350 that must have came out of a car at some point since it has a 2 barrel on it. Im going to be changing the intake manifold and carburetor to edelbrocks. However, I would like to know what a few things which are resting are on my manifold so I can delete them or hook them up if they are needed for something. All the old emissions equipment will go away as well, since none of them work anyway and just clutter the top of the engine.

Everything is color coded that im curious about so that the different angles you can see the same things.

When I put my new carb on, I will run a new line to the vacuum advance to the timed port, since it seems like HEI likes timed vacuum or something

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the factory put 2 barrel carbs on 350's it could be the original setup. your vin or rpo codes could verify that.

If your going to put a 4 barrel on remove the entire manifold and carb and put it on the shelf. You or a future owner may need to get it through emissions some day. and some of that stuff is getting hard to find. with the far left pushing for the "new green deal" we could end up with fed emissions testing some day.

Green is choke pull of it stays with the carb
Blue is basically a muffler so if you pump your brakes you dont loose vaccum to fast and stall the engine. probably should keep it even with a 4 barrel but not crucial.
Red thermal vacuum switch controls distributor vacuum, from manifold or ported. Usually for performance you use manifold vacuum.
Turquoise thermal switch controls temperature for when the EGR can come on.

 

[AuroraGirl]

Thanks for the welcome wishes!!

So you said red is a thermal switch for distributor vacuum? That sounds complicated. The others make sense.

The brake booster thing... so is that necessary? Should I keep it? Replace it? Does it filter or limit use?

This truck came standard with a 350 with a 4 barrel, this engine was dropped in by my grandfather about 30 years ago after he blew up his original one. He has since passed, but ive become the 2nd owner. Its a truck I use on property, so im not worried about keeping the emission equipment but no harm in keeping it. is all the EGR and stuff connected to the manifold and, minus vacc lines, come right off with the manifold?

 

[1987 GMC Jimmy]

The booster filter circled in blue makes sure you’re not sucking junk into the booster that’d damage the diaphragm and ruin the booster. The check valve that goes into the booster keeps vacuum in the booster to help mitigate the load on the engine when braking, mitigate a vacuum leak that would weaken the boost, or give you a reserve if the engine stalls.

 

[PrairieDrifter]

Everything can be simplified, the red can be deleted with an older style thermostat housing. Then with a new manifold and carb you should have ports to choose where to get vacuum for the advance.

Leave the brake booster line alone and just route it to a port on the intake for manifold vacuum.

With an aluminum intake and after market carb you only need vacuum to the advance and brake booster, and to the vacuum tank for the heater controls.

Possibly a one or two more depending on your transmission

 

[AuroraGirl]

Manual transmission. Clutch is a bitch to press at my weight lol. But it simplifies the situation. Heater controls are manual lines in the cab (no ac), so no need to worry there. Good to know. For the thermostat housing could I either find a threaded plug to fit on it or vaccuum plug the switch?

 

[PrairieDrifter]

Manual transmission. Clutch is a bitch to press at my weight lol. But it simplifies the situation. Heater controls are manual lines in the cab (no ac), so no need to worry there. Good to know. For the thermostat housing could I either find a threaded plug to fit on it or vaccuum plug the switch?

I like simplicity and clean looks even if my truck isn’t anywhere near show quality, which was why I suggested a a different style thermostat housing. But you should be able to find a plug for it, if that’s the best option for you, should be regular pipe thread. And if that doesn’t work out you can just get vacuum caps for the vacuum ports.