# Brakes, low vacuum?



## kjk990 (Sep 1, 2010)

I replaced my four wheel manual drums in my 67 GTO with Right Stuff four wheel disk kit. It is a huge difference but I think my cam isn't allowing enough vacuum to get the maximum performance. 

When I come to a stop the peddle feels like it comes to the bottom. It's not all the way to the floor, it just comes to a point it won't go any further. At that point, if I put it into neutral while still holding the brake peddle down, then give it a little gas at the same time, the peddle goes down another inch or so. 

If I do that same procedure while I'm moving, the car comes to a much easier stop. 

The other option to get better braking is downshifting my automatic transmission, as the RPMs come up a little, the braking gets much better. 

Am I correct in thinking I have low vacuum? 
My vacuum hose is connected to the manifold. Is there a stronger or more consistent vacuum?
I've seen vacuum reservoirs and pumps. Would one of those help?

Thanks


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## jmt455 (Mar 26, 2012)

The vacuum pump might help, but before spending another dime I would ask the folks at Right Stuff what minimum vacuum level is required for the proper operation of their system.

Then check your engine's manifold vacuum at idle to see if it meets that minimum level.

If your engine vacuum at idle is at or above the minimum required for their system to work properly, then you can proceed (with their guidance) to determine what's wrong with the installation or the parts.

If your engine isn't producing sufficient vacuum, you'll need to make decisions about eliminating the power boost, adding a vacuum pump or hydroboost system, or learning to live with it, if that is even a possibility.


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## 05GTO (Oct 6, 2004)

If you've checked and found no vacuum leaks you could change the cam for one with a higher LSA. Do you have a rough idle?


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## kjk990 (Sep 1, 2010)

I have to get a vacuum gauge, then I will check the vacuum.

Yes I have a rough idle.


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## 05GTO (Oct 6, 2004)

I have the same problem with my 67 which has a 108-110 LSA cam, I'm nervous when I attend cars shows with one foot slightly pumping on the gas to get enough vacuum for the power brakes to stop the car. But the car really has a great sounding idle, so I've just learned to live with it.


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## BearGFR (Aug 25, 2008)

If it's a vacuum problem (sounds like it very well could be) and you don't want to change the cam, then the two most popular options (other than full manual brakes) are an electric vacuum pump or a hydroboost system. I'm running hydroboost on my car. Go to the parts store and get an inexpensive vacuum gauge. If you don't have at least 15" of idle vacuum, then that's likely your problem.

You can get an off-the-shelf hydroboost for about a grand, or engineer your own from parts like I did for about $500.

Bear


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