vacuum brake conversion kit - wrong master cyl.???

[at7we2]

Hey guys, I'm in the middle of doing a vacuum brake conversion on my '87 and I've run into an unexpected snag. I've got the booster and master cylinder bolted into place, but when I tried to connect the brake lines, I realized they are not even close to lining up with the connections on the master cylinder. The lines fit dead-on perfectly with the powermaster, but they connections on the new vacuum setup are too high and too far toward the front of the car.

Here's a picture of what I have, is this the correct master cylinder?? If not, what does the correct one look like and what vehicle do I need to get one from?

Thanks,
Rob

 

[JDSfastGN]

they sometimes need to be bent a bit. Looks like they will go in without much trouble to me but the pic may be deceiving

 

[at7we2]

just went and looked at it again. the rear (smaller) line *could* be pursuaded to connect to the rear port with a little bending. *However* the front (larger) line is no where near connecting to the front port and it looks like it would have to bend back over on itself in a very sharp u-bend in order to line up. If I try to just gradually bend it, the coiled part of the line hits the power steering resevoir.

can someone post pics of their vacuum brake installation? I'd like to see what your master cylinder and brake lines look like.

Thanks,
Rob

 

[at7we2]

ok....nevermind

I just had to stare at it for a while and get pi$$ed-off enough to *make* the lines fit!

all connected now. just need to install the vacuum block and bleed the system.

Thanks for the post JDSfastGN.

Rob

 

[GNregistry]

How did you do that

Interested in converting to vacuum, how did you do it? Is there a manual to read or print to read and see how you did that...

How much work, time and parts needed, why did you switch?

Brett
GNregistry@aol.com

 

[POWERBRAKEBOB]

Hydroboost Vs Vacuum Vs Powermaster

That master is a two stage type. It has a larger piston to the front brakes. It will be pretty stiff to push, when it is bled out. It looks like a truck master. The standard Regal vacuum booster/master combo used a 24mm, or 15/16" piston. The pedal also has to be replaced with one from a vacuum braked car, or the valve body (plastic) will break, causing a major vacuum leak, and hard pedal. The larger reservoir always goes to the front brakes, using the 1/2" threads. The truck master lines are sometimes reversed. Don't forget to read the "hydroboost?..." threads here.

 

[at7we2]

That master is a two stage type. It has a larger piston to the front brakes. It will be pretty stiff to push, when it is bled out. It looks like a truck master. The standard Regal vacuum booster/master combo used a 24mm, or 15/16" piston. The pedal also has to be replaced with one from a vacuum braked car, or the valve body (plastic) will break, causing a major vacuum leak, and hard pedal. The larger reservoir always goes to the front brakes, using the 1/2" threads. The truck master lines are sometimes reversed. Don't forget to read the "hydroboost?..." threads here.

not truck parts. all the parts are for a normally aspirated g-body. the dual diaphragm booster is what came on the later 80's g-bodies. the pedal feel is very smooth and easy, although it does feel different than the powermaster. it's a very simple procedure to unbolt the powermaster parts (including pedal) and replace with the vacuum setup. all parts use the same bolt holes. the hardest part is removing the powermaster brake pedal, but it really is no big deal once you figure out which tools to use. I highly recomend using a "Gear-Wrench" or similar ratcheting box wrench to remove the old brake pedal and install the new one. but it could be done with standard box wrenches.

 

[at7we2]

Interested in converting to vacuum, how did you do it? Is there a manual to read or print to read and see how you did that...

How much work, time and parts needed, why did you switch?

Brett
GNregistry@aol.com

Very, very easy. The parts swap took less than 3 hours not including bleeding the brakes. I probably could have done it in even less time but I got distracted and ended up fixing a couple of wiring issues I found under the dash.

As far as a manual, I purchased a complete kit from another board member and it came with a brief but effective step by step explanation of the process. The process basically goes like this:

1. disconect battery
2. remove brake fluid from powermaster resevoir with turkey baster or syringe
3. disconnect electrical connections from powermaster
4. disconnect brake lines from master cylinder
5. remove old brake pedal
6. remove four nuts under dash holding powermaster to firewall
7. lift powermaster out of engine bay
8. put on steel toe boots and punt powermaster as far as you can being careful not to hit innocent bystanders :biggrin:
9. insert four mounting studs on vacuum booster through existing mouting holes in firewall
10. reuse four original bolts from powermaster to bolt vacuum booster to firewall (underdash)
11. install new brake pedal
12. connect brake lines to master cylinder
13. bleed entire brake system.
14. install TTA style vacuum block with port for vacuum brake booster
15. connect vacuum hose from vacuum block to vacuum booster with inline filter
16. reconnect battery
17. carefully test brakes

as for why I switched, this is the third turbo Buick I've owned and I've had problems with the powermaster in all of them. I've owned several normally aspirated g-bodies and they all had excellent brakes (same parts as what I installed on this GN) and I've read plenty of positive posts about the conversion. I've also talked to a few local guys who are running vacuum brakes and they have zero complaints. I decided to give it a try for myself.

HTH
Rob

 

[JDSfastGN]

glad you got it and its working ok. I haven't quite gotten used to the vacuum brakes yet on mine but they feel pretty good.