I recently bought this '86 IROC, 305 TPI and as I was working on the engine noticed a vacuum hose coming off the brake booster and going nowhere.


I looked in the service manual and it pictures it going to some kind of filter then it looks like it goes to the base of the carb.


I cannot find anything even closely resembling that filter, plus I have TPI and all the vacuum ports are accounted for. Where does this hose go, what will I need, and how do I hook it all up??


Thanks!

 

First, how does the brake pedal feel when the engine is idling in park?
What page of the service manual are you looking at?

 

Long story short I bought the car from a guy who had taken off all the TPI and put a 4bbl carb on it. It ran like garbage and I am in the process of putting all the TPI back on.


I've only driven the car off the trailer and into the garage but I do remember it being VERY hard to stop when backing off the trailer. Like trying to stop when the engine is off.


Looking at page 5-9 in the brakes chapter.

 

It's not a "filter", exactly; it's actually a check valve.

Since you have TPI, you don't have a carb; so ... yeah. But, there should be a port on the side of the plenum for it. See this post here https://www.thirdgen.org/forums/tech...iagrams-i.html and hook your motor up accordingly.

{edit} more info in your new post while I was typing...

The reason the brakes didn't work right was because that hose was disconnected.

 

Everything I've seen shows that port on the plenum going to the PCV valve..??

 

The brakes are not part of the "engine", and therefore aren't on the diagram. They're part of the "car".

Common sense:

Hook up everything you see on the diagram for your engine. When you are done, there will be ONE port left over; a HUUUUJJJJJJJJJE one. Hook your brakes to it. (get a check valve off of some random car at the boneyard)

 

I stand corrected. the PCV valve connects to the intake manifold. I have every other port on the plenum taken. Where exactly is it??

 

Been awhile since I last saw one of those; seems like it's on the driver's side toward the rear but my memory fades. Like "they" say, memory is the 2nd thing you lose when you get old, but dammit, now I forgot what the 1st one was supposed to be.

 

Very good! Put that TPI back on!! I'll help you because you are wise.
Here's some pics where that hose from the brake booster goes. HTH. Good luck!

 

You guys rock! Sure enough, I pulled the plenum off and he had it plugged. Just need a fitting and I'm good to go. Is that check valve necessary?

 

Absolutely. Every make & model car, truck, van, etc. has one.
Um, except with brake systems that use hydro-boost from the power steering pump, and not engine vacuum for power brakes. Maybe that's where the previous owner was headed...

EDIT: Also radical cam profiles have low engine vacuum at RPMs approaching idle. You may have a rad cam dude, whereas you think it's running like crap...

 

No rad cam. I was told by ding dong the cam was "one step" above stock. We'll see..


Anyway, is this the check valve? I think it's still there.

 

yeah, that's a check valve to hold a vacuum in the booster in the event that the engine dies and you still need good brakes to come to a complete stop.. but that's not the one that goes inline, which is put there to keep gas fumes from eating up the big rubber diaphragm inside the booster. i've been driving my Camaro for 3 years now with no inline check valve and it still works... just hook it up without it, and if you stumble across one in a junkyard (GM put the same one on literally every car and truck they built in the 70's thru at least the mid 90's with vacuum assisted power brakes, so should be easy to find) you can put it in.. i don't think Ford of Dodge every put anything like this in anything they built, so it might not be absolutely necessary..