Vacuum Brake question

[Evilttz]

Switched by Powermaster over to a Vacuum system and I was wondering what would be a good vacuum source to tap into?
Thanks

 

[T-CHRGD]

Best is to get a new vacuum block with an extra port designed for the vacuum brakes. :biggrin:

 

[Evilttz]

Thanks, Where can I get a new Vacuum block with the extra port?

 

[T-CHRGD]

I would think most Buick vendors would carry them.
Kirban's, GBodyParts, etc. Links on the bottom of the main forum page.:biggrin:

 

[Red Regal T]

Switched by Powermaster over to a Vacuum system and I was wondering what would be a good vacuum source to tap into?
Thanks

I like cutting in right above the PC valve and installing a 3/8" T with the odd leg going to the booster. You run the 3/8" hose behind the coilpak and connect. The vacuum block requires you donate $40 for one, and have this unsightly, out of place, fat hose going to the booster.

 

[GUNMETAL T-TYPE]

Im doing my conversion in the mourning and was wondering the same thing good thread

 

[Nick Micale]

I like cutting in right above the PC valve and installing a 3/8" T with the odd leg going to the booster...........

Just make sure you use a metal tee, NOT a plastic one.

I agree with John, why mess with the vac block replacement as it can also be a real PIA.

 

[scot w.]

I like cutting in right above the PC valve and installing a 3/8" T with the odd leg going to the booster. You run the 3/8" hose behind the coilpak and connect. The vacuum block requires you donate $40 for one, and have this unsightly, out of place, fat hose going to the booster.

I agree 100%, This is what I have done years ago on my white T-Type and it stops remarkably well for vacuum brakes!


Scot W.

 

[JimP]

As mentioned above get your self a T fitting and tap into an existing vac source. Don't use a hose that's too large either to the booster. If the hose is too large (diameter) it won;t work as well. 3/8 hose should be perfect.

 

[Nick Micale]

As mentioned above get your self a T fitting and tap into an existing vac source. Don't use a hose that's too large either to the booster. If the hose is too large (diameter) it won't work as well. 3/8 hose should be perfect.

You bring up a good point about the proper hose.

A good auto parts store will stock 11/32" brake hose that is stronger than vac hose, and will not collapse on the inside as is gets old and tired.

 

[meanchicken]

How much boost should a properly functioning vacuum brake system with S-10 wheel cylinders in the back, be able to hold at the line?

 

[meanchicken]

How much boost should a properly functioning vacuum brake system with S-10 wheel cylinders in the back, be able to hold at the line?

Howdy.
Anyone?:redface:

 

[1quick6]

I don't have any personal experience with vacuum and holding boost, but I would think you should be able to do as well as a PM as long as your brakes are in overall good condition. Once your booster has vacuum to assist, it's not going to get sucked out while building and holding boost at the line due to the check valve. Now, if you are road racing, that's a different story. You'd be in and out of boosting and braking, so that could present problems.

I think the advantage hydroboost offers is the increased line pressure, which seems to overcome deficiencies in the braking system, such as small rotors/pads/calipers. Any of the braking systems do quite well if the overall health of the entire system is good.

 

[Nick Micale]

................I think the advantage hydroboost offers is the increased line pressure, which seems to overcome deficiencies in the braking system, such as small rotors/pads/calipers. Any of the braking systems do quite well if the overall health of the entire system is good.

I know you said "I think" when stating HB offers increased line pressure, and even if it does, the limiting factor in braking is the ability of the tires NOT to skid.

I do agree with you that the HB offers an increase in line pressure, but I have found that the vac system also has an difference in line pressure.

This is NOT due to the method of assist, but the difference in the master cylinder piston sizes.

When I started doing vac conversions in the mid-90's, it was because the stopping performance was lacking with the PM, and my customers wanted an improvement.

When testing a PM equipped GN, I found only the front tires would skid in a panic stop, so this indicated to me not enough rear braking effort.

After the vac system was installed, same testing showed all 4 wheels brakes evenly.

To take this a step further, when changing to a manual master cylinder set up, it also was much better than the PM.

 

[meanchicken]

Sorry for the hijack of your thread Evilttz...just didn't see a need to start a new thread on vaccum brakes and figured this is good info for you too.

Thanks for the feedback, guys.

When I was at the track a cole months back, best my PM would hold was about 7-8psi before the rear tires (MT 275/60/15 drag radials) would start to spin...yup....started spinning my tires while staged and brake boosting...that was embarassing...:redface:

I still was hitting 11.6's.

So as long as the vacuum brakes can do at least this good....I'll be happy.

 

[1quick6]

I know you said "I think" when stating HB offers increased line pressure, and even if it does, the limiting factor in braking is the ability of the tires NOT to skid.

I do agree with you that the HB offers an increase in line pressure, but I have found that the vac system also has an difference in line pressure.

This is NOT due to the method of assist, but the difference in the master cylinder piston sizes.

When I started doing vac conversions in the mid-90's, it was because the stopping performance was lacking with the PM, and my customers wanted an improvement.

When testing a PM equipped GN, I found only the front tires would skid in a panic stop, so this indicated to me not enough rear braking effort.

After the vac system was installed, same testing showed all 4 wheels brakes evenly.

To take this a step further, when changing to a manual master cylinder set up, it also was much better than the PM.

I am sure the vacuum systems performed nicely since they've been doing so for years. In your many conversions, I am sure you went the extra mile to make sure the rest of the braking system was in good health, thus ensuring increased performance. I am sure not everyone does this, so they perceive the vacuum systems as inadequate when it was really only inadequate installation that caused their grief.

My PM brakes performed pretty well even before I switched to hydroboost. It was well maintained. I was just bored and took on a project, knowing it would head off expensive repairs in the future and possibly give me more holding power at the line. It wasn't really a vac vs hydro situation to me. I drove turbo Regals with all three types of brake systems prior to switching and I just preferred the pedal feel of hydroboost.