Power master to vacuum conversion question.

[SCOOBY DOO]

Vacuum conversion here...zero issues...stopped on a dime.

 

[~JM~]

I'd be leery of a vacuum conversion. If the last owner hadn't done it I would have gone hydroboost. My vac brakes wont lock up the tires on an emergency stop. Not even close. Almost hit a car because they pulled out in front of me. Both feet on the pedal and it hit the pedal stop. Yes all the valves are working, yes i've bleed the brakes, yes it has the proper vac pedal, and yes the rear drums are adjusted properly. Just not enough stopping power in my opinion. There's also a huge "dead spot" in the pedal. It moves like maybe 2 inches before actually doing anything. My old 87 with the PM didn't have that problem.

Shouldn't be like that. Something isn't quite right. Mine works well, just won't hold much boost at starting line.

 

[TIMINATOR]

My 9" has half inch wider, and 1" bigger diameter drums, and with a wide variety of wheel cylinder sizes available, I think I will be able to hold some boost. I may be able to drive it tomorrow!
TIMINATOR

 

[grandnat_6]

I'd be leery of a vacuum conversion. If the last owner hadn't done it I would have gone hydroboost. My vac brakes wont lock up the tires on an emergency stop. Not even close. Almost hit a car because they pulled out in front of me. Both feet on the pedal and it hit the pedal stop. Yes all the valves are working, yes i've bleed the brakes, yes it has the proper vac pedal, and yes the rear drums are adjusted properly. Just not enough stopping power in my opinion. There's also a huge "dead spot" in the pedal. It moves like maybe 2 inches before actually doing anything. My old 87 with the PM didn't have that problem.

Maybe I should go the hydro boost route instead. Does the hydro boost cost more money? I know it works with the power steering system. I wonder what happens when the engine stalls. Do you still have some normal function braking ability like the vacuum system?

Thanks.

 

[TireFryer]

Shouldn't be like that. Something isn't quite right. Mine works well, just won't hold much boost at starting line.

Maybe I’ll go through the system again.

Hydroboost is more expensive yes. Others who actually have experience can chime in about the other questions

 

[TIMINATOR]

Buicks use an electric motor and pump for the pressure, and a cylindrical/ball reservoir for emergency stops if the pump/ motor fails. As with vacuum brakes, you still have power brakes in an emergency, at least till the Hydraulic pressure is used up, (or vacuum for normal power brakes) then you have manual brakes and need both feet for a panic stop.
TIMINATOR

 

[grandnat_6]

In either conversion system; how does the on dash brake light work? There must be something you need to plug into the system?

 

[TType85]

In either conversion system; how does the on dash brake light work? There must be something you need to plug into the system?

Dash brake light comes off the proportioning/distribution block on the frame rail; drivers side near the trans I think.

 

[blackazz]

I switched to a booster and a break bandit.
Pedal is so nice no rock hard pedal after boosting. And always enough vaccum to stop.

 

[Chuck Leeper]

A 3700# car with puny ass <11" disc brakes is always a gamble, unless there's some testing done.
1. Correct booster and pedal linkage?
2. Correct master cyl?
3. Sufficient engine vac?
4. Correct pads? Lots of choices there.
I/we use a brake pressure gauge to see what is REALLY at the wheels.
A case in point:
55 Chevy with the 9" rear drums, Buick/Chevelle style ft rotors D154 caliper's, AIRC.
Engine made about 12-14" vac.
Booster dual diaphram 8".
Mc is a 1.125" bore Wilwood.
Wilwood adjustable prop valve.
MAX ft wheel psi with max pedal pressure = 650PSI. Should be at least 1200.
Tried 3 pad combos.. Still no stop.
Hydraboost: Same brake combo. 2100PSI!
At those pressures I smoked 2 sets of pads and one set of rotors, just testing.
Went to EBC pads, required I use reduced pedal effort.
A brake pressure gauge is not expensive.
I get the HB units from Ebag. Elliott Sydnam makes them for me.

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[grass doctor]

why are we still talking about this .......chuck ended the thread...vacuum your car and/or floor and best for brakes on a TR

 

[CzyKats44]

Vacuum conversion here...zero issues...stopped on a dime.

X2, never looked back. (I've had PM and HB on other cars)

 

[earlbrown]

I'd be leery of a vacuum conversion. If the last owner hadn't done it I would have gone hydroboost. My vac brakes wont lock up the tires on an emergency stop. Not even close. Almost hit a car because they pulled out in front of me. Both feet on the pedal and it hit the pedal stop. Yes all the valves are working, yes i've bleed the brakes, yes it has the proper vac pedal, and yes the rear drums are adjusted properly. Just not enough stopping power in my opinion. There's also a huge "dead spot" in the pedal. It moves like maybe 2 inches before actually doing anything. My old 87 with the PM didn't have that problem.

You've got something wrong going on with your brakes.


Vacuum brakes have hauled down millions of Regals (and other G-bodys) over the decades with no problem.

I can lock my front brakes up at the drop of a hat with a vacuum setup. And that's with a 215/220 roller cam and heavely ported heads with O/S valves.

 

[TireFryer]

You've got something wrong going on with your brakes.


Vacuum brakes have hauled down millions of Regals (and other G-bodys) over the decades with no problem.

I can lock my front brakes up at the drop of a hat with a vacuum setup. And that's with a 215/220 roller cam and heavely ported heads with O/S valves.

What should I check? I know it has a vacuum pedal. How do I check the master? I'm going to bleed the brakes and do a fluid flush this weekend.

 

[Chuck Leeper]

What should I check? I know it has a vacuum pedal. How do I check the master? I'm going to bleed the brakes and do a fluid flush this weekend.

I already made a list...
Get busy and look.

 

[grandnat_6]

Thanks. I forgot the light was hooked to the proportioning valve.

One last quick question. Why hook the vacuum to the vacuum lines that see boost? Why not plumb it to the intake before the turbo or use the elbow that hooks into the passenger side valve cover breather that most of us block off anyway?

Thanks everyone!

 

[TIMINATOR]

The intake is the only part that sees vacuum! And it sees boost....
No vacuum in front of turbo....
TIMINATOR

 

[earlbrown]

Thanks. I forgot the light was hooked to the proportioning valve.

One last quick question. Why hook the vacuum to the vacuum lines that see boost? Why not plumb it to the intake before the turbo or use the elbow that hooks into the passenger side valve cover breather that most of us block off anyway?

Thanks everyone!

If you have enough vacuum in front of the turbo, you're intake is WAY to restrictive.


On the upside, the car would be so slow, you wouldn't even need brakes.

 

[SCOOBY DOO]

Scoob approved part for the vacuum conversion...but the vendor is your deal. I got mine from FT a million years ago...but I don't see it on their site.

1986 1987 Buick Regal Grand National Turbo T T-Type GNX VACUUM BLOCK WITH EXTRA VACUUM FITTING FOR VACUUM BRAKES #6797

www.kirbanperformance.com

 

[SteveZ82]

Went with Earl's kit. Threw my powermaster on the shelf and covered it so I never have to look at it again. Had zero issues with the conversion. Stops on a dime luckily because some asshole pulled out in front of me yesterday.