Where does this pipe go?

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.

clickittyclank

Junior Member
Joined
Jan 2, 2026
Posts
29
Reaction score
25
Location
Texas
First Name
C
Truck Year
1987
Truck Model
r1500
Engine Size
350
Putting the engine back after a rebuild and can't remember/figure out were this pipe went. Having trouble finding it in any of the photos I took so hopefully one of y'all can help a dude out. I'm fully aware of how ridiculous this is haha. Thanks in advance!

1987 GMC Sierra Classic
5.7L 350 - automatic transmission
edit: TBI - knew I was forgetting something.
You must be registered for see images attach
 
Last edited:

YakkoWarner

Full Access Member
Joined
May 29, 2024
Posts
644
Reaction score
1,052
Location
Central Texas
First Name
Wolf
Truck Year
1989
Truck Model
R2500 Suburban
Engine Size
454
If it has a flare fitting on the threaded end I'd guess vacuum line to the brake booster, but I'm not sure how you'd thread it into the intake if its not a flare nut.
 

clickittyclank

Junior Member
Joined
Jan 2, 2026
Posts
29
Reaction score
25
Location
Texas
First Name
C
Truck Year
1987
Truck Model
r1500
Engine Size
350
That was my first thought as well but we already have the brake booster connected to a similar looking pipe which looks correct based on the images before it came out.
 

Attachments

  • IMG_2206.JPG
    IMG_2206.JPG
    157.1 KB · Views: 48

DoubleDingo

Full Access Member
Joined
Jul 3, 2012
Posts
13,908
Reaction score
23,763
Location
Right where I am
First Name
Bagoomba
Truck Year
1981
Truck Model
81-C20 Silverado Camper Special-TH400-4.10s
Engine Size
Carb'ed Vortec 350
The pipe in the first photo looks to be the same exact pipe in post #3. Do you maybe have more than one and now simply have an extra?
 

clickittyclank

Junior Member
Joined
Jan 2, 2026
Posts
29
Reaction score
25
Location
Texas
First Name
C
Truck Year
1987
Truck Model
r1500
Engine Size
350
It's possible I suppose but pretty sure I didnt have an extra pipe in the truck. Thinking it goes somewhere else that I'm overlooking. First photo's pipe is also much cleaner over all. Maybe connects somewhere a little more protected? Appreciate yall's replies, will get this figured out at some point.
 

DoubleDingo

Full Access Member
Joined
Jul 3, 2012
Posts
13,908
Reaction score
23,763
Location
Right where I am
First Name
Bagoomba
Truck Year
1981
Truck Model
81-C20 Silverado Camper Special-TH400-4.10s
Engine Size
Carb'ed Vortec 350
It's possible I suppose but pretty sure I didnt have an extra pipe in the truck. Thinking it goes somewhere else that I'm overlooking. First photo's pipe is also much cleaner over all. Maybe connects somewhere a little more protected? Appreciate yall's replies, will get this figured out at some point.
I saw one was cleaner, the shape looks the same
 

clickittyclank

Junior Member
Joined
Jan 2, 2026
Posts
29
Reaction score
25
Location
Texas
First Name
C
Truck Year
1987
Truck Model
r1500
Engine Size
350
Yeah it’s a head scratcher. The extra pipelator mystery continues.
 

AuroraGirl

Full Access Member
Joined
Sep 8, 2019
Posts
10,710
Reaction score
8,239
Location
Northern Wisconsin
First Name
Taylor
Truck Year
1978, 1980
Truck Model
K10, K25
Engine Size
400(?), 350
What is the brake booster vacuum line going to it’s just out of frame in the photo?
You must be registered for see images attach

To me it seems like a pcv line but possibly intended for a different tbi application like a car or a gmt400 maybe. The booster In your truck is going to something between the the metal pipe and the booster before going to the metal pipe
 

clickittyclank

Junior Member
Joined
Jan 2, 2026
Posts
29
Reaction score
25
Location
Texas
First Name
C
Truck Year
1987
Truck Model
r1500
Engine Size
350
Yeah it goes to a brake booster filter, whatever that is, then up to the valve. I’ll look through my book and see what the pcv setup is supposed to look like. Thanks for chiming in.
 
Last edited:

CalSgt

Full Access Member
Joined
Oct 3, 2021
Posts
2,254
Reaction score
5,414
Location
CA
First Name
Casey
Truck Year
1980
Truck Model
Chevy K-10 Custom Deluxe
Engine Size
350
Power steering?
 

AuroraGirl

Full Access Member
Joined
Sep 8, 2019
Posts
10,710
Reaction score
8,239
Location
Northern Wisconsin
First Name
Taylor
Truck Year
1978, 1980
Truck Model
K10, K25
Engine Size
400(?), 350
Yeah it goes to a brake booster filter, whatever that is, then up to the valve. I’ll look through my book and see what the pcv setup is supposed to look like. Thanks for chiming in.
Brake booster filter, interesting didnt know the TBI had one. Its not super needed on TBI but it cant hurt. just make sure its vertical at all times
 

ButchM

Full Access Member
Joined
Oct 19, 2023
Posts
74
Reaction score
105
Location
Idaho
First Name
Butch
Truck Year
1986
Truck Model
K30
Engine Size
454
I would first look for a flare fitting connection of that size on the intake manifold that was empty, that would be a start.
 

ButchM

Full Access Member
Joined
Oct 19, 2023
Posts
74
Reaction score
105
Location
Idaho
First Name
Butch
Truck Year
1986
Truck Model
K30
Engine Size
454
I'll dig thru my books and see what pics may be available.
 

bucket

Super Moderator
Staff member
Moderator
Joined
Aug 3, 2010
Posts
35,135
Reaction score
43,739
Location
Usually not in Ohio
First Name
Andy
Truck Year
'77, '78, '79, '84, '88
Truck Model
K5 thru K30
Engine Size
350-454
The pipe in the first photo looks to be the same exact pipe in post #3. Do you maybe have more than one and now simply have an extra?

I'm just quoting this because it is most likely correct. It's a brake booster pipe and one is already installed on the engine. The uninstalled one looks bent, however.
 

Forum statistics

Threads
48,419
Posts
1,067,007
Members
42,806
Latest member
that_orange_c10
Top