87’ Silverado vacuum lines

Hello all!

I’ve got a 1987 Silverado TBI. All of the vacuum lines that are related to the TBI and emissions need replaced. And I’m not totally sure they’re all there that are supposed to be there.

Question 1.
There’s a larger one off the back behind the throttle body coming out of the intake. I believe this used to run to auto trans. I swapped this truck over to a standard about ten years ago.

Should this outlet just be plugged?

Question 2.
What all vacuum lines should be in place for the engine to run appropriately as it did stock.(not worried about the vacuum lines for the A/C until later on)

Question 3.

What size I.D. vacuum lines do I need and where do said applicable sizes run to and from?

Thanks to all in advance for your help.

This truck was originally my grandfathers and I’m trying to get it up and running again to drive around on my off days. I’ve added a photo of the truck for those who may be interested in the shape it’s in.

It would be difficult to find anyone with a 1987 with all those vacuum lines intact. Even more difficult to find one with a factory standard and 4wd like yours.

But I just happen to know a guy...

Awesome thank you! Is that one running from front of throttle body to valve cover on passenger side . And another running from top of throttle body to driver side valve cover?

Also vacuum on the MAP sensor runs back behind the throttle body it looks. Is that correct?

I’ve got a picture of the bigger (I believe) vacuum behind the throttle body that comes from the intake. Maybe you can help me out with what I need to do with that.

Also those larger vacuum lines. Can an OEM replacement be purchased that you know of? Or do I have to make one with vacuum tubing?

Thanks again!!

The big one on the front of the throttle body goes to the PCV on the passenger side valve cover.

The one from the rear of the spacer between the throttle body and air cleaner housing goes directly into the driver side valve cover.




That one in your pic feeds a couple of things. On mine it feeds (or pulls) the Cruise Control and it goes into the cab and could possibly be part of the AC... not sure.

Thanks for the photos and help! Waiting on some parts to come in. I will update when I get them put on, replace the vacuum lines, and see what it does.

Thanks again!!