Inliners International Forums General Discussion Drive Train 292 brake booster vac port?

I'm adding a brake booster to my '68 C10 with 292, and I'm not sure where to connect the vacuum hose. I've got to find a hose first, but it appears to require a large diameter.

I'm assuming I need to hook up to the intake. Is there a standard spot on the 292 intake for brake booster vac hose?

There's nothing obvious on my intake, but there is a small hole on the left side.

[This message has been edited by cruiserman (edited 05-17-2003).]

I had a '62 292 in my '74 GMC 3500, but the carb was the original '74 single barrel and it had a tube directly in the bottom rear of the carb about the size of the gas line that hooked directly to the brake vac hose with a check valve. It needs to get full manifold vac. A lot of the small ports on later carbs are regulated for various smog purposes and not suitable for vac brakes. You could just tap into the intake if there is no tap with a plug already. Just don't let any thread shavings get into the engine.

I figured the port on the passenger side of the carb on the intake would be the location, but the PO put on a little air cleaner, etc. The port is hooked up to the PCV valve. I'd like to find a paper filter air cleaner and go back to stock setup instead of oil bath. I've got a picture somewhere . . . see the black hose left of the carb?




Edited to fix PCV .

[This message has been edited by cruiserman (edited 05-18-2003).]

The hose you've pointed out in the picture is for the PCV hose, like you said.

The intakes that were set up for power brakes had a square-ish flat boss on the intake manifold directly below the carb on the drivers side. It appears that the shiny pipe in the foreground of the picture is routed to a fitting at that location. Is that true? If that's the case, then you can put an adapter on that fitting for multiple vacuum hoses. By the way, where does that shiny pipe go to back behind the engine? It's obviously not a fuel pipe, but it looks to be 3/8" diameter.

If there is no fitting there, then the safest way to drill a hole is to take off the manifold, lay it on it's side, and then drill and tap for a fitting. Then you can blow out all the chips with compressed air before reinstallation. Usually a 90-degree 3/8" pipe thread by 3/8" hose fitting is used. You can use 1/4" thread if you can't get 3/8", as the hole is a little smaller. It'll still work.

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David
newbie #4153

[This message has been edited by just a six (edited 05-18-2003).]

Hi again, David. I thought about doing a dual port, but wasn't sure if something like that is available. I'm averse to removing the intake from past experience, but this one looks to be pretty easy.

I don't know about the pipe, but it appears to go the tranny (Powerglide). I need to check that out.

Thanks again, Eric

cruiser,

It seems to me that a dual connection on the PG fitting would be a lot easier and should work well. I vaguely remember that PG operates by vacumn. After all, you won't be using the brakes and PG at the same time. Neither uses much vacumn (Volume)

If you choose to tap, put heavy grease on the drill bit and tap, the grease will catch most of the chips. After that I would try a shop vac to clean out the remaining chips, but the best way is to remove the carb and put a small suction tube inside the intake to get everything.

Forgot one thing. If you remove the intake manifold only be sure to tighten it first before you tighten the bolts connecting the two manifolds together last or you can crack a manifold. Do not overtighten any of these bolts.

I wouldn't take them loose at all because at least two-five of them will be so rusted they will break off, misery!! The double port is the way to go.

Will do. Thanks for the advice.

I picked up a 3 brass fitting setup to make a T to get 2 ports for the tranny and the brake booster. Hopefully this will work.

Edit:
I got everything installed, and the booster is leaking like a sieve. I think the booster is missing seals on front and rear. Is there a seal kit available for Delco boosters?

[This message has been edited by cruiserman (edited 05-20-2003).]

You need a check valve on the manifold to booster line. This gives you a couple of brake uses if the engine quits and may be your problem.

Your booster diaphragm may also be leaking, this is a common problem. I have the same problem on my Ford fire truck and hate to have to tackle that job because it is buried under the frame. I would like to repair it but doubt that any repair kits are available. Sure would save a bunch of bucks.

The rear of the booster seldom leaks unless the diaphragm is junk. On the front of the booster, where the master cylinder bolts on, there is supposed to be a black neoprene seal that seats down in the hole. It's called a "face seal." You can purchase them new from a dealer, as long as you call it by the right name, they should be able to get one for you if it's missing or torn up.

There are only 2 sizes, one for early model boosters and one for the later units that uses the plastic reservior "quick take-up" type masters.

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David
newbie #4153

This one is supposed to be off a '72. It has a zinc finish on it, and is quite large.

Is the face seal air tight? I figured not.