1981? 350 in a C20 - Vacuum/sensor questions

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Oldbear42

Supporting Member
Supporting Member
Joined
Feb 15, 2024
Posts
65
Reaction score
153
Location
Linden, Alberta, Canada
First Name
Shaine
Truck Year
1981
Truck Model
C20 LWB Scottsdale
Engine Size
350
The one you marked tvs and the one you marked you don't know are both. Tvs just to control different items if one is open cold meaning you can blow through it cold but not hot,it controls the EFE ,that's the valve on the exhaust manifold,sounds like you are going g to headers so I won't bother explaining hookup or function. If the other one you can blow through hot but not cold it probably controls egr. The port I see with the screw in it is ported vacuum so all good leave it plugged.
Thank you for the information/testing for the valves.

The one port with the screw is getting a proper vacuum cap as soon as I get back to the shop at work next week - I like to use proper stuff when I can.
 

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
4,067
Reaction score
5,918
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
Thank you for the information/testing for the valves.

The one port with the screw is getting a proper vacuum cap as soon as I get back to the shop at work next week - I like to use proper stuff when I can.
I use machine screws in vacuum hoses all the time, in my opinion they're preferable and cheap. Most of the vacuum plugs these days split on the end in short time. I buy new machine screws and screw them into short pieces of new vacuum hose. But I was letting you know that the one pictured was for ported distributor vacuum advance,which I wouldn't run,so plugged is good. But I need to see where the vacuum advance is hooked up now to see if it's on manifold vacuum. Machine screws are not tapered and the threads aren't deep enough,so they don't split or cut the hose. Pick up a few different sizes to have an assortment on hand.
 

Attachments

  • Screenshot_20240327_233014_Google.jpg
    Screenshot_20240327_233014_Google.jpg
    74.9 KB · Views: 7
Last edited:

Geoduck

Junior Member
Joined
Nov 26, 2023
Posts
24
Reaction score
41
Location
PNW
First Name
Dan
Truck Year
1985
Truck Model
C10
Engine Size
305

Attachments

  • 692FA2C4-CC9C-4829-8DF5-8A3E97EB312C.jpeg
    692FA2C4-CC9C-4829-8DF5-8A3E97EB312C.jpeg
    118.5 KB · Views: 7

Oldbear42

Supporting Member
Supporting Member
Joined
Feb 15, 2024
Posts
65
Reaction score
153
Location
Linden, Alberta, Canada
First Name
Shaine
Truck Year
1981
Truck Model
C20 LWB Scottsdale
Engine Size
350

Oldbear42

Supporting Member
Supporting Member
Joined
Feb 15, 2024
Posts
65
Reaction score
153
Location
Linden, Alberta, Canada
First Name
Shaine
Truck Year
1981
Truck Model
C20 LWB Scottsdale
Engine Size
350
I use machine screws in vacuum hoses all the time, in my opinion they're preferable and cheap. Most of the vacuum plugs these days split on the end in short time. I buy new machine screws and screw them into short pieces of new vacuum hose. But I was letting you know that the one pictured was for ported distributor vacuum advance,which I wouldn't run,so plugged is good. But I need to see where the vacuum advance is hooked up now to see if it's on manifold vacuum. Machine screws are not tapered and the threads aren't deep enough,so they don't split or cut the hose. Pick up a few different sizes to have an assortment on hand.
I have a big stack of Equipco parts bins in my shop - three of the drawers have my machine screw collection (imperial, metric, etc). This screw has most likely held for a decade so it should be fine - I'll just keep a few vacuum caps/plugs in the glove box so that Murpgey's Law doesn't strike...
 

Oldbear42

Supporting Member
Supporting Member
Joined
Feb 15, 2024
Posts
65
Reaction score
153
Location
Linden, Alberta, Canada
First Name
Shaine
Truck Year
1981
Truck Model
C20 LWB Scottsdale
Engine Size
350
Here is a link to the Jungle Seller vacuum port plug set/kit I use:

https://www.amazon.com/dp/B09XN2VSZM/
We have a large assortment at my work's shop that we can pick through as needed. It's the same stack of parts bins my new door hinge pins and bushing came from. But I might have to grab a kit to keep some in my home stock. Partsman habits die hard.
 

Latest posts

Forum statistics

Threads
42,137
Posts
909,894
Members
33,633
Latest member
satansdad
Top