What is this hard line under the TBI plumbed to the Intake?

[jblaven]

What is it? I don't seem to have a comparable place on the GM Vortec Intake for it.

See the blue arrows. Not sure what it is for... I went back outside to look at the part. The hard line run along the length valve cover towards the firewall then turns 90 degrees (horionitally) behind the end of the valve cover, then 90 degrees vertical. Any ideas? I am sure I need to block off or "T" a line if I don't use it on my new intake, so I really need to know what it is.

[RJGeister]

I think it's for the power brakes. I would have to look at mine to be sure. I will let you know.

Rich

[jblaven]

Ah, thanks. Wow, I wouldn't have guessed that. I did a google search and found another thread where a guy tapped/threaded a TBI spacer. Funny thing is, I actually have the spacer already. I just need to get the tap for that size. I should be able to come pretty close to the angle and location of the original opening on the original intake.

[jblaven]

Originally Posted by jblaven

Ah, thanks. Wow, I wouldn't have guessed that. I did a google search and found another thread where a guy tapped/threaded a TBI spacer. Funny thing is, I actually have the spacer already. I just need to get the tap for that size. I should be able to come pretty close to the angle and location of the original opening on the original intake.

Talked to a guy today and we both feel that tapping into one side of the spacer into just one port may not be the best thing (having uneven vacuum). After reading some more, it appears that I need to tap the back of the intake instead.

[Berg]

I'm sure the uneven vacuum shouldn't be a problem and it works fine in factory configuration. The only time it will draw vacuum is when you use the brakes so it shouldnt be a big deal

[jblaven]

Originally Posted by Berg

I'm sure the uneven vacuum shouldn't be a problem and it works fine in factory configuration. The only time it will draw vacuum is when you use the brakes so it shouldnt be a big deal

In the factory configuration, it is below the TBI and pulls vacuum from the intake. After reading about how the inside of the TBI barrels have a certain level of polish (for fuel to flow) and how the spacer continues with the same idea, I felt that drilling a "hole" into the side of one of these barrels (albeit the spacer and not the actual TBI itself) may not be the best solution.

I did decide to use the threaded NPT opening directly behind the TBI. I am sharing it with the vacuum that is needed for the baffles for the heat/air in the dash. I picked up a "T" adapter that had the correct diameter ends. Two of the ends were large enough for the brakes. The other was smaller and went to the firewall for the baffle.

I was glad not to have to thread another hole in my new intake!

[Berg]

That sounds like a better alternative and less work too. It'll look cleaner in the end. That's probably the same port the carb'd intakes used to use. I know my older cars and trucks have the same type of deal you just plumbed up.


These are 2 GM fittings that are in a few of my Chevelle catalogs. They are meant for the sole purpose of splitting the rear vacuum port in the intake manifold. I wasn't sure if yours had the hole in it already or not. I bought a cheap polished Vortec 4 barrel manifold that came with vacuum ports and extra coolant fitting taps from ebay. I thought it was going to be a piece of crap but it turned out to be a decently machined manifold.