Vacuum Brake Conversion

[mike67goat]

Gather up all the parts you'll need. Don't forget a large jug of BRAND NEW brake fluid too. No reason to use some old stuff that's been absorbing water for years.

First is removing all the Powermaster stuff.

Standard safety stuff here... Make sure to depressurize the system (odds are if you're doing his is because you don't have any pressure in there. lol), And keep some rags handy to mop up any spilled brake fluid. It makes plastic look good but will eat up some paint!

Once the two electrical plugs are removed, take the two brake lines and two mounting nuts loose. I find that vacuum caps make great seals for the exposed brake lines.

Next, remove the under dash cover and remove the clip that holds the Powermaster rod to the brake pedal. It helps to have a second person under the hood to move the Powermaster but it can be done alone. After it's disconnected from the pedal, it can be removed.

Then remove the adapter plate that converts from the 4 bolt mount on the firewall to the two bolt mounting pad for the Powermaster.

This little part is the reason there's two different pedals. It causes the Powermaster to point down a few degrees and as a side effect causes the pin location on he pedal to be higher.

While you're under there, remove the pedal as well.

Install the vacuum diaphragm and master cylinder.

Notice the front and real lines have been swapped relative to the Powermaster. Front is not rear and rear is not front. Much like doggie style.Luckily, thanks to the additional spacing of the booster one of them lines right up. The larger of the two lines need to be curled up to mate with the front of the master cylinder.

If you trust yourself not to kink the lines, it can be bent with your thumbs. If you don't feel that confident you need a tubing bender. Oddly enough the ones you can rent from the auto parts store wont' work. The one you need comes from a home improvement store like Home Depot. That one will go down small enough to handle the small brake lines. It can be found in the plumbing section.

Once the line is tweaked it can be attached to the master cylinder.



Once the pedal is out it can be modified to accept the new pin for the vac brake kit.

Measure 1-1/4" down (center to center) and closer to the edge. That is the new location for the pin. Notice the edge of the pin is now parallel with the large flange on the Powermaster pin.

Drill a 13/32 hole at that location. Then drill that hole out to 7/16" but ONLY go 1/3 of the way through. This is to get the pin started so that it can be pressed into place.

Put the pin on position with the cotter pin hole facing vertically and miss the Powermaster pin. Then smack it in place with a framing hammer. ...or if you have an arbor press, press, or vice I guess that will work too

Note: This is the "no weld / press fit" method. If you have a welder or a torch, feel free to start out and 7/16" and weld it.

Once the pin in installed the pedal can be put back in the car. Notice with this method the car can be returned to stock without having to drop the pedal again. You also don't have to lose sleep at night and feel shame knowing there's a Chebby part on your Buick!

Next is to run the vacuum line to the engine. Route the hose under the coil pack and tee into the PCV hose. Put the check valve before the tee. That way you'll keep from sending boost into the booster and it'll also keep boost from hitting the PCV valve. Bonus!
Another way is to get a aluminum vacuum block for the throttle body that's set up like a TTA with the vacuum port sticking out the side. I don't really care for how those look but to each their own.


Now that all the connections are made, all that's left is bleed the brakes and do a final inspection.

YICK!!

Now is also a good time to toss the 30+ year old rubber lines and upgrade to stainless lines. Not only would it be a safety upgrade but a performance upgrade as well. Since the system is opened and needs bleeding, it would be the perfect time.

All you have to remove is the wheels and they're already off.

There's no rerouting necessary. Just tuck the plugs under the harness or let them fall where they will.

 

[mike67goat]

Thank you for all of the great photos, very helpful, I have 1986 GN, brakes went to floor pulling out of my garage. Where did you buy the kit , the pin seems to be the trick,can I buy the rest at any parts store?
Is there a gasket between the booster and the firewall. Again your a lifesaver for us. mike67goat

 

[Johnnie]

I purchased the entire kit from kirban's .... Including the pedal. Not the cheapest way to go, but I had everything I needed at hand... And instructions came with it. And yes, if memory serves me correctly( and someone correct me if I am wrong) there is a gasket between the booster and firewall. I haven't regretted it at all. Just remember, you can't go immediately from boosted to hard braking ( unless maybe if you have some sort of vacuum reservoir) and if you have a big cammed motor, you might not have enough vacuum for the booster. My motor is stock.

 

[earlbrown]

You need to test your check valve then (the little black piece that snaps into the booster and accepts the 3/8" hose. On my car I used a redundant check valve where I tapped my intake manifold just because I had one.

Keep in mind, when you do a throttle chop, vacuum goes through the roof. It sounds like you might be running conventional squishiy vac hose to your booster and it's getting sucked shut (I knew a girl in high school that could do that). If that's the case, you won't get any brake assistance until the vacuum drops enough to transmit a (weaker) signal to the booster.

 

[Geezy]

Any one know the part number for the gasket that goes between firewall and booster? And where can I hook up the power brake filter? I am using a vacuum block. Any pictures? Thanks for all the help

 

[Johnnie]

Keep in mind, when you do a throttle chop, vacuum goes through the roof. It sounds like you might be running conventional squishiy vac hose to your booster and it's getting sucked shut (I knew a girl in high school that could do that). If that's the case, you won't get and brake assistance until the vacuum drops enough to transmit a (weaker) signal to the booster.

Thank you earl. That is something I did not know. I guess I shouldn't assume stuff. Still a steep learning curve for me !

 

[mike67goat]

You need to test your check valve then (the little black piece that snaps into the booster and accepts the 3/8" hose. On my car I used a redundant check valve where I tapped my intake manifold just because I had one.

Keep in mind, when you do a throttle chop, vacuum goes through the roof. It sounds like you might be running conventional squishiy vac hose to your booster and it's getting sucked shut (I knew a girl in high school that could do that). If that's the case, you won't get and brake assistance until the vacuum drops enough to transmit a (weaker) signal to the booster.

Thanks for the HEADS UP,, Was her name Margaret H ?

 

[mike67goat]

Thanks for the HEADS UP,, Was her name Margaret H ?

 

[earlbrown]

Any one know the part number for the gasket that goes between firewall and booster? And where can I hook up the power brake filter? I am using a vacuum block. Any pictures? Thanks for all the help

It's just plain ole squishy foam. Every master cylinder I've pulled left that gasket intact. If yours managed to get torn just get a kit from wal*mart or homodepot to seal up a door then use the scrap to make a new gasket.


On the filter, you can put that anywhere you want on the vacuum line. It's just there to keep gas fumes off the booster's internals and mess up the internal bladder. It can be anywhere on the line that looks good or out of the way.

 

[earlbrown]

Thanks for the HEADS UP,, Was her name Margaret H ?

Angie S (she looked at me after the first time and said ''i've been told I can suck start a Mac truck''.

I believe her.


....so about this Margaret.....

 

[Geezy]

It's just plain ole squishy foam. Every master cylinder I've pulled left that gasket intact. If yours managed to get torn just get a kit from wal*mart or homodepot to seal up a door then use the scrap to make a new gasket.


On the filter, you can put that anywhere you want on the vacuum line. It's just there to keep gas fumes off the booster's internals and mess up the internal bladder. It can be anywhere on the line that looks good or out of the way.

Thank you very much for the info! Really apprciate it

 

[Tori]

Notice the front and real lines have been swapped relative to the Powermaster. Front is not rear and rear is not front. Much like doggie style.Luckily, thanks to the additional spacing of the booster one of them lines right up. The larger of the two lines need to be curled up to mate with the front of the master cylinder.

Need some clarification on your post.... Regarding the line orientation. In the top picture with the original PM installed the large line is in the front.,
then the next pic with the booster installed, you show the thinner line mounted to the rear (indicating the the large line will go to the front again. But, the instructions say to swap positions of the lines. Another member showed his lines with the large line to the front also.

Can someone clear this up ?

 

[GNRick]

Tori, as stated earlier, the lines will only connect one way to the new master. When I installed my Hydroboost I had to switch the lines.

 

[Tori]

Thanks Rick, i read that but the fittings on my car look to be the same size.

So are is the large tube supposed to be at the front, or rear ?

 

[GNRick]

Thanks Rick, i read that but the fittings on my car look to be the same size.

So are is the large tube supposed to be at the front, or rear ?

Per this thread the front brake line is the smaller of the two. Does that help? http://turbobuick.com/threads/replacement-brake-line-help.401054/#post-3273389

 

[Tori]

no, that doesn't really help. Because that contradicts the two pictures posted above.

 

[Coelacanth]

In my comment posted earlier in this thread, I linked to a series of videos documenting this exact procedure, and it specifically states you need to swap the lines. It will still function if you don't swap them, but you'll lose braking power because the fronts need to do most of the work, and won't be able to do this as effectively if you have the front line going to the wrong part of the master cylinder.

 

[87GNSteve]

I dont know about this swapping lines thing, I have an NA regal and the larger line is up front. I believe if you get the correct master cylinder the lines do not need to be swapped since it is a stepped bore. The power master did not have the stepped bore.

 

[Tori]

In my comment posted earlier in this thread, I linked to a series of videos documenting this exact procedure, and it specifically states you need to swap the lines. It will still function if you don't swap them, but you'll lose braking power because the fronts need to do most of the work, and won't be able to do this as effectively if you have the front line going to the wrong part of the master cylinder.

I've read this entire post, saw all the photos, and watched the 3 videos you linked. The videos are for a hydroboost install. Forgive me for not assuming the same install procedure would carry over for the vacuum boost install.

Thats why i've asked the question, i wanted a clear, cut and dried confirmation of which was correct as the post has conflicting information.

 

[Coelacanth]

Thats why i've asked the question, i wanted a clear, cut and dried confirmation of which was correct as the post has conflicting information.

Yes there certainly is, and it would be good to have that question clarified: If doing the Powermaster to vacuum brakes swap, do you reverse the lines? It seems that you don't need to, but that some bending is needed.