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Discussion Starter #1
I have a high lift cam in my L72. There is not enough vacuum feeding the brake booster, so my front power disc brakes do not work.

Anybody have a recommendation? Vacuum reservoir? Electric vacuum pump?

Are electric vacuum pumps noisy?
 

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How much vacumn does the motor make? Pulling off what source? Stock cam?
If you suspect you have a hole in the booster diaphragm, you could be misunderstanding the problem. Have you verified the booster will hold vac? You should also have a vacumn check valve at the booster , feeding the line. That thing sometimes cracks and leaks.
 

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There is not enough vacuum feeding the brake booster, so my front power disc brakes do not work.
When do they not work?
When u are coming up to an intersection with engine braking and high vaccuum?
Or when u are stilling in your driveaway pumping the brakes?
Or when u have filled up the gas tank and idling across the forecourt to the kerb to enter the street?

Basically in the real practical world at idle u dont need any vaccuum or boosted brakes cuse unles u are on a hill with the E brake off u have manual brakes... all other time u have high rpms high vaccuum and usually engine braking which is even higher vaccuum still.

Anything over 5 to 7" at idle is sufficient.. and if u need more ..at idle...then dial the idle advance and the idle circuits in carb to best STABLE idle... issue solved.
 

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Discussion Starter #4
How much vacumn does the motor make? Pulling off what source? Stock cam?
If you suspect you have a hole in the booster diaphragm, you could be misunderstanding the problem. Have you verified the booster will hold vac? You should also have a vacumn check valve at the booster , feeding the line. That thing sometimes cracks and leaks.
Yes, pulling off high lift cam. Booster works. Check valve is fine.
 

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Hydro-Boost is the best solution if you have a power steering pump. The next best would be a mechanical vacuum pump off of a modern diesel engine where you will have to make your own custom brackets to mount it to your motor based upon the length of a belt that fits the application. Either that or go for a diesel pick-up before the mechanical pumps that used an electric vacuum pump.

Cadillac used an electric vacuum pump back in the early sixties but it was a supplemental pump to the engine vacuum and not designed to pull a hard vacuum like the diesel pump is. Diesels don't have manifold vacuum because they are open to the atmosphere to maximize cylinder filling (with direct injection there is no mixing of fuel and air out side of the cylinder.

If you have a street strip car that is more strip than street you could install a Moroso vacuum pump and tap into that for brake booster vacuum and still get better ring seal. Of course if it where mine I would loose the power assist and go with manual brakes.

Larger Dave
 

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Discussion Starter #6
Hydro-Boost is the best solution if you have a power steering pump. The next best would be a mechanical vacuum pump off of a modern diesel engine where you will have to make your own custom brackets to mount it to your motor based upon the length of a belt that fits the application. Either that or go for a diesel pick-up before the mechanical pumps that used an electric vacuum pump.

Cadillac used an electric vacuum pump back in the early sixties but it was a supplemental pump to the engine vacuum and not designed to pull a hard vacuum like the diesel pump is. Diesels don't have manifold vacuum because they are open to the atmosphere to maximize cylinder filling (with direct injection there is no mixing of fuel and air out side of the cylinder.

If you have a street strip car that is more strip than street you could install a Moroso vacuum pump and tap into that for brake booster vacuum and still get better ring seal. Of course if it where mine I would loose the power assist and go with manual brakes.

Larger Dave
Thank you Dave.
 

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why not make/buy a vacuum can
I made one out of a small propane tank and it works great
While thinking out loud, Do you have vacumn head lamp doors, if not , that vacumn can will fit neatly on the fender and look stock and its near the booster.

But really, I don't think cheating the brake booster of its necessary vacumn. Ready to go hydra-booster if you have a ps pump?
 

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While thinking out loud, Do you have vacumn head lamp doors, if not , that vacumn can will fit neatly on the fender and look stock and its near the booster.

But really, I don't think cheating the brake booster of its necessary vacumn. Ready to go hydra-booster if you have a ps pump?
no headlight doors
here is a picture.
 

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Discussion Starter #10
While thinking out loud, Do you have vacumn head lamp doors, if not , that vacumn can will fit neatly on the fender and look stock and its near the booster.

But really, I don't think cheating the brake booster of its necessary vacumn. Ready to go hydra-booster if you have a ps pump?
No vacuum head lamp doors. Yes, I do have a PS pump.

Thanks for the pic.
 

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No vacuum head lamp doors. Yes, I do have a PS pump.

Thanks for the pic.
Well ,if you have a ps pump, then all you need to do is decide hydra booster.
 

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HydraBoost is found on diesel powered pick-up trucks and vans and on most medium duty trucks and buses if they didn't have air brakes. Here is a Hydraboost installed along with a hydraulic clutch (which why there is a hose going into the brake reservoir):.



Here is the part you need off the donor vehicle:



Big Dave
 

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have u actually driven the car?
Read mypost above again.. and aply to real life situation
?If u have over 5 or 7" that more than enough.. if u dont then something else is wrong.. like dialing in the idle carb/ dizzy specs for THAT engine
I have been driving daily for 30 odd yrs on low idle vaccuums...
 

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Discussion Starter #17
have u actually driven the car?
Read mypost above again.. and aply to real life situation
?If u have over 5 or 7" that more than enough.. if u dont then something else is wrong.. like dialing in the idle carb/ dizzy specs for THAT engine
I have been driving daily for 30 odd yrs on low idle vaccuums...
They don't work in most situations.

Still working on it. Carb may be the issue.
 

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Put a vaccuum gauge in the car .. THEN u will see and feel the brakes will operate exactly as I describe
When u are above idle say 1200 rpms u will have enough vaccuum for brakes with the most wild of street cams
When u slow down/ take your foot off the throttle the engine vacuum suddenly goes real high

And when u put your foot to the metal u have about 1" of vaccuum....but unlikely u will be using then brakes then anyway..
and once the engine produces enough vacuum about 7" u have at least 2 usually 3 to 4 complete pedal down up release , before the boster looses its vaccum... and that will be like say sitting on a hill, no e brake on , holding with foot brake rolling down, engine idleing or not runing.
 

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Put a vaccuum gauge in the car .. THEN u will see and feel the brakes will operate exactly as I describe
When u are above idle say 1200 rpms u will have enough vaccuum for brakes with the most wild of street cams
When u slow down/ take your foot off the throttle the engine vacuum suddenly goes real high

And when u put your foot to the metal u have about 1" of vaccuum....but unlikely u will be using then brakes then anyway..
and once the engine produces enough vacuum about 7" u have at least 2 usually 3 to 4 complete pedal down up release , before the boster looses its vaccum... and that will be like say sitting on a hill, no e brake on , holding with foot brake rolling down, engine idleing or not runing.
I have a similar problem, but I am not sure what you are saying. I understand some of it.
 

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I live at the top of a very steep hill

my car idles @1300 rpm. when I first took the car down the hill, I had very little to no brakes. I thought I would bust a brake I was pushing so hard.
I installed that little vacuum can and it solved my problem
 
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