What is this Fitting?

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tpripps

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Location
Scandia, MN
First Name
Tyler
Truck Year
1978
Truck Model
C30
Engine Size
454
I'm taking inventory of all of the things that are broken on my "new" truck and one of the things I found was this fitting. One of the barbs is snapped off. I'm not sure if it's vacuum or some sort of cooling/heating line. I assume it's vac otherwise the system wouldn't hold pressure... maybe it doesn't... I haven't gotten it running yet. Anyway, what is this fitting called and where can I buy a new one?


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dsteelejr

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Hudson, WY
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David
Truck Year
1973, 1980
Truck Model
Cheyenne super C20 camper special, Sierra K25
Engine Size
350, 454
I forgot the name of it, but it’s purpose is to send vacuum when the engine is at operating temp. It receives vacuum from the carb and transfers it to the other lines, but only after the engine has warmed up. I had an ‘84 K5 about 20 years ago and had to deal with that crap and from what I remember it’s for actuating smog devices based on whether the engine has reached operating temp, hence the reason its mounted on the water neck. It will only heat up once the thermostat is open.
 

Jimbarry

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California
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Jim
Truck Year
1983
Truck Model
C30
Engine Size
454
Pretty sure it's called a thermal ported vacuum switch. I'm transferring mine to dsteelejr's manifold which arrived today. Thanks again!! As stated above it opens when hot and provides vacuum when engine is up to temp. If you need more info I'll let you know for sure when I start putting mine back together and figure out where it went.
 

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tpripps

Full Access Member
Joined
Aug 23, 2021
Posts
64
Reaction score
52
Location
Scandia, MN
First Name
Tyler
Truck Year
1978
Truck Model
C30
Engine Size
454
Pretty sure it's called a thermal ported vacuum switch. I'm transferring mine to dsteelejr's manifold which arrived today. Thanks again!! As stated above it opens when hot and provides vacuum when engine is up to temp. If you need more info I'll let you know for sure when I start putting mine back together and figure out where it went.
BINGO!!! That's it! Quick google search and that's exactly what I need! THANKS!
 

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