What is this?

[tadslc]

Circled in Yellow

One of the nipples broke off the other day.

Several vacuum lines go to it. Looks like it's threaded into the thermostat housing.

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1981 C-10 305

Thanks,
Tad

 

[45tt]

Possibly a flush & fill access? But I suspect I’m wrong.

 

[Ricko1966]

It's a thermo vacuum switch. How many hoses on it and where do they go. And don't just say carb there are multiple ports on the carb.

 

[Bextreme04]

Like Ricko said, i is a thermostatically switched valve. There can be several of them and they can do various functions. They will show up as a "TSV" on your vacuum diagram and often are used to switch when the vacuum advance canister is activated and when the EFE(heat riser crossover) valve is actuated based on engine temp. They are pricey and mine are simply bypassed.

 

[tadslc]

From memory there are 3 possibly 4 vacuum lines attached and like I said, it's located on the thermostat housing and is the only solenoid.

 

[Ricko1966]

It's not a solenoid, and it hasv3 maybev4 hoses attached is not enough info.They've only used like 100 of these over the years to control blah blah blah. And I don't have everyone of them for every year every option every engine combo memorized.Like I said, how many hoses and where do the go to. I'm trying to help but I need correct info. I'm thinking it is the tvs for the EGR/EFE. But correct info will confirm this.

 

[tadslc]

Roger that, I'll do more research and get back to y'all.

 

[tadslc]

Problem solved, I just Glue'd the nipple back on.

But to answer your question, it has 4 nipples total and with various T's and such they go everywhere. To the distributor, to the carb, to some diaphragm on the the carb. It's the orange one.

I would like to know what it is and do I really need it.

Thanks,
Tad

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[Ricko1966]

Yes you need it, you could route around it but with your expierience level at this point I'd say leave it alone looks like it controls. Vac advance. EGR. And vacuum tip in.

 

[tadslc]

Yes you need it, you could route around it but with your expierience level at this point I'd say leave it alone looks like it controls. Vac advance. EGR. And vacuum tip in.

Thanks, I have a ton of experience on everything except American cars, they are so foreign...

 

[Craig 85]

The orange valve is actually called a "ported vacuum switch." I looked up Napa, Oreilly's and Rockauto. All show a 4 port switch for an '81 C20 with a 305, but it's black. Many of these switches are color coded and I believe it relates to the temp at which the inter switch moves to allow vacuum to go through the different ports.

Rockauto is a great place to search for parts even if you don't buy there. When you click on the info tab for a part it will usually give you OEM part number to cross reference. FYI I found an Airtex #7P1066 is a good number but is out of production. This may help you find a direct cross reference if you need to find a replacement.

https://www.rockauto.com/en/catalog...ical-switch+&+relay,ported+vacuum+switch,4604

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[80BrownK10]

Yes you need it, you could route around it but with your expierience level at this point I'd say leave it alone looks like it controls. Vac advance. EGR. And vacuum tip in.

I see the same and I agree with that recommendation

 

[Ricko1966]

AC Delco OEM it's called a thermo vacuum switch. Standard ignition calls them ported vacuum switches, other manufacturers call them thermal vacuum control valves. OE hose schematic lists them as tvss. Name isn't that important. The function is it turns on and off different vacuum operated accessories based on engine temperature.

 

[Vbb199]

Thanks, I have a ton of experience on everything except American cars, they are so foreign...

The irony in this statement.

 

[80BrownK10]

The irony in this statement.

Haha, that's why he said it. Just as Ironic as Toyota trucks now made here in the US and GM trucks made in Mexico?