Highest boost held with vaccum brakes?

[Cheeseburger]

Originally posted by Epitome
I'm just an amateur, but isn't boost level pretty irrelevant? I mean a 72 turbo at 10 lbs of boost is certainly exerting a lot more pressure on the driveline than a stock turbo at 10 lbs, right? Isn't it really the air flow at a given boost level that matters, not the boost level itself? I don't see how boost level is relevant (for seeing how much you can hold on the foot brake) unless you have the exact same combo. Someone slap me around if I'm wrong

True, that's why i said ''big cam and make power''.

When i had vacuum brakes i was running a 252ci stage 1 motor with a 4 bolt pt 70 and 224/224 cam that was in 1994.
I think the guys that are making power and holding boost with vacuum brakes are possibly using there emergency brake to hold boost....which well eventually bend your backing plates and more.

9 times out of 10 a person changes to vacuum brakes because its CHEAPER!!

 

[bruce]

9 times out of 10 a person changes to vacuum brakes because its CHEAPER!!

BTW, where did you get the 9 out of 10, and cheaper **fact**?.

Who really cares if it's cheaper, if the system is more reliable, and not prone to single application failures?. Not to mention finding parts on a vac system if it should fail, isn't a major project. As I recall, there's been lots of threads about guys buying rebuilt PMs, and having to do it 2-3 times before getting a good unit. No thanks, I have other things to do with my time, then wait for replacement parts, and replace faulty *new* parts.

For the guy wanting a stock looking car, by all means, the PM fits that bill. The vacuum system was good enough that in 89 the TTA had them. To some they might see it as just updating the system, like GM did.

 

[Cheeseburger]

Originally posted by bruce
BTW, where did you get the 9 out of 10, and cheaper **fact**?.

Who really cares if it's cheaper, if the system is more reliable, and not prone to single application failures?. Not to mention finding parts on a vac system if it should fail, isn't a major project. As I recall, there's been lots of threads about guys buying rebuilt PMs, and having to do it 2-3 times before getting a good unit. No thanks, I have other things to do with my time, then wait for replacement parts, and replace faulty *new* parts.

For the guy wanting a stock looking car, by all means, the PM fits that bill. The vacuum system was good enough that in 89 the TTA had them. To some they might see it as just updating the system, like GM did.

The reason why the trans am got vacuum brakes is because of very limited room under the hood.
Bonneville supercharged sse's also had the powermaster.
If your parts are failing 2-3 times you must not be installing them properly, i would get a competant mechanic to do your install.

I never heard of all these failures you seem to be talking about, otherwise i am sure their would have been a huge gm recall and pending lawsuits!

Maybe brakes are not your fortay

 

[bruce]

Originally posted by Epitome
I'm just an amateur, but isn't boost level pretty irrelevant?

Yes, especially when you change the code. What can be done, is use true launch control strategy, ie not to be confused with a stutter box.

 

[INEEDAGN]

We're not all tightwads

I can guarantee that my decision to switch was not cost related at all. I bought all NEW acdelco parts, and the bill came to over $400, and this was at my MOM's dealership, at a really good discount. WHY? Because I saw firsthand just how hard it was to stop with no powermaster assistance. No matter how big and strong of a guy you think you are, you arent stoppin' that mf'er in any short distance when that thing fails. What happens when vacuum assistance fails? It does get harder to stop but at least it can be stopped, and vacuum failures are much more uncommon. My 70K mile car came with receipts for two previous powermaster replacements, and that stack of paperwork only went back to the 50K mile range. Tell me that's reliable. If the TTA's, syclones, typhoons, or virtually any other turbo car really needed a better braking system, they would have gotten it. My powermaster is going in the corner of the shed, and the next owner can take the risk if he chooses.

God forbid you might have to add a vacuum pump to do high boost launches, It'd kill the originality.

bob

 

[Cheeseburger]

Well i said my piece It's been fun, and i still do not like vacuum brakes on a gn!
Bruce i was just having some fun with you on the ''competant'' thing.

Food for thought, how much vacuum do you think your motor makes under boost?
Yes it does have some in the booster but while staging and holding the brakes down it goes away real fast!

I'm done, good luck on your decisions!

 

[2 SLOW]

I noticed some people put in S - 10 wheel cylinders. I also see that everyone has different results with mods. I tried S - 10 cylinders and had to take them back out because they worked too well. On a hard stop they would lock up way before the fronts, and the back end wanted to trade places with the front. I didn't even want to try it in the rain. So I would be careful you don't get the front to back bias out of whack. At least that's what happened to me. And that's with two long shoes, not that I think it makes a difference.

 

[Turbo Indian]

what about a vacume accumalator you see these hot rod guys with the HUGE cams use. not that I've got any problems in the firebird with vacume brakes.

 

[Red Regal T]

Well, shame on you guys who chucked their powermaster to save money. Really, these guys that want to run low 10s and 9s etc., has no relation to normal TRs. Apples and oranges. After spending untold thousands on their motor, you're not going to slow up spending on what you need brake wise. Race cars use trans brakes or whatever they need to turn fast times. For "normal" 11 and 12 second TRs, you can't beat vacuum brakes for overall effectiveness, reliability, and cost.

 

[denn454]

i think this is the first time i've seen people, other than me, complaining about the vacuume brakes. i have them on mine, the previous owner said the pm failed so he switched to vacuume. i later found a burned out brake fuse . but i absolutely hate mine. it recently occured to me after i parked my car that maybe the check valve is in wrong. but i honestly have had cars with non-power brakes stop easier. this thing is a complete joke in my oppinion.

but a lot of people use them with no problems so i'm sure they can and do work. my thoughts are for a street car vacuume is the way to go (if yours works...) but i'm wanting to switch back to the pm for racing reasons. theres nothing worse than having to do a quick burnout and fly up to the lights so you can stage before the other guy. i'd like to prestage, build boost and creep up, do that with vacuume and you better be holding on, you won't jsut creep up.

 

[Welby]

The T I bought in Oct. has a vacuum conversion, and it's horrible. Holding boost? Yeah right, I'm more concerned with being able to stop period let alone holding any boost.
The brakes won't lock up no matter how hard I slam them, and they feel like there are 2x4's for pads/shoes. It's actually semi-scary, the few times I got to drive it I kept some serious distance behind cars, lol.
In all fairness, I put the car right into storage, and haven't had a chance to look at the brakes at all, or at least bleed them. The guy I bought it off of said the rotors, drums, pads and shoes were new. Scary thought considering the way they *cough* work.
Looking forward to spring so I can get it sorted out

 

[bruce]

Originally posted by denn454
i think this is the first time i've seen people, other than me, complaining about the vacuume brakes. i have them on mine, the previous owner said the pm failed so he switched to vacuume. i later found a burned out brake fuse . but i absolutely hate mine.

Before you spent the money on doing that, try investigating putting some real brakes on the car. The tiny front rotors just aren't up to the task of working well on a modified GN. While the Baers are $$, the B Body conversion is semi$$, but the latest 02 Camaro conversion can be done for alot less then either of the above. And they can shut the car down in a real hurry. The 02 Camaros use a 12" rotor, that's 1.25" thick, and a dual piston caliper. They have the necessary mass and dimensions to effectively work at stopping a GN after a fast pass.

Oh, and before nixing the vac brakes you might make sure it has the right master cylinder on it. There are a number of M/Cs that look the same, but have different internal parts. Not to mention that some are packaged wrong, when getting rebuilt ones.

And you might also check the brake lines, and fluid. If you drive your GN hard, then you should be flushing the brake fluid at least annually. With the tiny rotors, and limited thermal sinking, they put alot more heat into the fluid then you might expect, and that reduces the effectiveness of them, ie soft pedal. If you still using the stock oem brake lines, you might even think of updating to the Russel Stainless Steel lines.

With my vac setup, 02 front brakes, PST rear discs, and little tweaks, I really doubt there's anything that's going to stop much better then my car. And yes, tweaks includes high rate front springs to keep the bumper off the ground during hard braking.

Sorry to rant, but I got a *thing* about brakes, and fast cars....

 

[Red Regal T]

Originally posted by Welby
The T I bought in Oct. has a vacuum conversion, and it's horrible. Holding boost? Yeah right, I'm more concerned with being able to stop period let alone holding any boost.
The brakes won't lock up no matter how hard I slam them, and they feel like there are 2x4's for pads/shoes. It's actually semi-scary, the few times I got to drive it I kept some serious distance behind cars, lol.
In all fairness, I put the car right into storage, and haven't had a chance to look at the brakes at all, or at least bleed them. The guy I bought it off of said the rotors, drums, pads and shoes were new. Scary thought considering the way they *cough* work.
Looking forward to spring so I can get it sorted out

Well, I don't have all the stuff that Bruce has mentioned, but my brakes are damn good. Pulls down fast from speed. I don't care that much about holding boost, but if you read this thread, some guys hold a lot, so it's doable. If your car is not stopping properly, something is wrong and it's not because they're vacuum brakes. Best advice I can give you is, fix it!

In fact, I just changed over a turbo T this morning. Took off that junk PM, and didn't even have to bleed the system. Anybody want to buy a malfunctioning PM cheap?

 

[Welby]

Yeah, I'm definitely going to take care of it. If you don't mind, when I drag the car out in the spring, I'll shoot you over some pics of how it's set up. Maybe you can spot something obvious that's wrong with it. I know it has a "T" off of the PCV valve for the booster hose.
On the boost gauge, at idle there is about 18 in. of vacuum if I remember right. Pics would probaby tell alot more than I can

 

[tes87gn]

Vacuum Brakes

I converted to vacuum brakes and it's the best thing I've done to the system. Not only does it work better, but it looks MUCH cleaner under the hood. PM are ugly and tempermental as hell. I also did the larger shoes and S-10 cyl. I can hold back as much as 12psi and maybe alittle more at the line.Of coarse I have to give credit where credit is due I thought the Vacuum upgrade was a horrible idea too until Bill Anderson showed me the trick to it now I'd have it no other way.....................Well except for a trans brake.

 

[Red Regal T]

Originally posted by Welby
Yeah, I'm definitely going to take care of it. If you don't mind, when I drag the car out in the spring, I'll shoot you over some pics of how it's set up. Maybe you can spot something obvious that's wrong with it. I know it has a "T" off of the PCV valve for the booster hose.
On the boost gauge, at idle there is about 18 in. of vacuum if I remember right. Pics would probaby tell alot more than I can

Sure, any help I can give. I have the TTA block on both my TRs. I just did a conversion today and did the PCV hookup. Seemed to be fine.

 

[TurboJim]

Originally posted by Cheeseburger
The reason why the trans am got vacuum brakes is because of very limited room under the hood.
Bonneville supercharged sse's also had the powermaster.
If your parts are failing 2-3 times you must not be installing them properly, i would get a competant mechanic to do your install.

I never heard of all these failures you seem to be talking about, otherwise i am sure their would have been a huge gm recall and pending lawsuits!

Maybe brakes are not your fortay

The bonneville SSEi's had ABS, the electric booster was used to pressurize the system under an ABS stop. They used this pressure for power assist too. Now they do it in a hydraulic unit and most cars are back to good ole vacuum brakes. Vehicles that see low vacuum for long periods, like trucks will usually have hydroboost. Which uses the power steering system to pressurize the assist section.

As for Powerbastard failures, I feel I am, and was at the time, a extremely competent TECHNICIAN, not mechanic. ASE thought so, Shell's Auto Care program thought so, AAA thought so, the state of NJ thought so, and my boss thought so. Anyway, mine failed one morning on the way to work coming to a busy intersection. I bent my seat pushing to try to slow down. Thank GOD the light was green! Like Bruce, mine was a single application failure. I switched to vacuum not because it was cheaper, but because manual brakes are better than no brakes!!! I am with Bruce on this one!

I can hold 5-7 or so psi in my car, which is a lot more power than many at 15psi for whatever thats worth. I havent tried to hold more really.

 

[TurboJim]

Originally posted by bruce
Before you spent the money on doing that, try investigating putting some real brakes on the car. The tiny front rotors just aren't up to the task of working well on a modified GN. While the Baers are $$, the B Body conversion is semi$$, but the latest 02 Camaro conversion can be done for alot less then either of the above. And they can shut the car down in a real hurry. The 02 Camaros use a 12" rotor, that's 1.25" thick, and a dual piston caliper. They have the necessary mass and dimensions to effectively work at stopping a GN after a fast pass.

Bruce, you by chance got a parts list for this camaro conversion?

Did you need to chance the prop/metering valve and/or use a larger bore master? Did you need special backspacing wheels or will the normal wheel fit?

 

[DonnieShort]

I switched to vacuum brakes a few years ago, and it's by far one of the best things I've done. I got my kit from Red Regal T and it has worked perfect. Oh, and as far as holding boost, I have the big wheel cylinders and use the large shoes from 2 sets of shoes. I can hold 20psi on the footbrake any time I want. Launching at 14psi on the footbrake get's me mid 1.5 60' times. So don't try and tell me that vac. brakes doesn't work. As long as your brake system is up to snuff there's no reason they shouldn't work.

 

[GNVYUS 1]

I got the Caddy pump for my 69 GTO about 6 years ago right from the dealer new at $225. I warn you though, its noisey, but does work very well. I plan on using it on Reds vacuum kit this summer.

Why would you use the PCV valve for your brake booster?
I would feel much safer with the TTA block that has the big port FOR the brake booster.

Big shoes and cylinders are a must on any GN looking to pull a good 60 ft. With the weakmaster I could only hold 2 psi and then the tires would smoke at the light ( which was cool when I was 20 ) but without those mods you can not hold squat back there.

The factory fronts suck big time. I did a write up on t6p on the Aerospace kit which only costs $675 ( without lines ). That bolt on kit will give you false teeth on an emergency stop.