Aftermarket brake Boosters

[Lippyp]

Who's using one of these? Are they easy to fit and will I need new brake lines to fit it? Its a 67 with drums all round. I have an ad for a used factory set up in the classifieds at the moment but am also considering a new aftermarket setup as at least that way I know its not gonna crap out on me in six months. My rightlegs ghetting tired and having recently driven a friends 68 Impala 427SS with drums all round but with a power booster I can't go back to my old stand up and pray manuals. Mind you, now the front shoes have been replaced and put in the same way on each side they might be a little better!

[Bob Moore]

I think Jugernot was going to use one on Lemon Drop. Contact him.

Good luck - Bob

[Lippyp]

Anyone else running one?

[Lippyp]

Is the stock Brake Booster the same for disks at the front and drums or were there different ones for each setup. I've been offered a stock setup from a disk braked truck and want to know if it'll work with my drum setup.

[dave2953]

I'm not absolutely certain, but I don't think there are differences between the boosters. I know our years had either Bendix for Delco, but I think they were the same internally. I think the difference is the pressure applied to the front or rear. If you go from drum to disk you'll need a proportioning valve to keep the rears from locking up. Hope this helps.

[shifty]

Originally Posted by Lippyp

Is the stock Brake Booster the same for disks at the front and drums or were there different ones for each setup. I've been offered a stock setup from a disk braked truck and want to know if it'll work with my drum setup.

I don't agree with you, Brad.

This is the lowdown as I understand it:

If you are running all discs, you do not need a proportioning valve.
If you are running all drums, you do not need a proportioning valve.
If you are running disc/drum mix, you need a proportioning valve.

The purpose of the proportioning valve is to balance the amount of pressure placed on the disc brakes as opposed to the drum brakes. One requires more than the other, so the valve is required to prevent one from locking up when the other is just getting to operational pressure.

The all-disc and all-drum setups just use a distribution block that normally has a pressure indicator on the underside of it that is tied into your console.

I tried time and time again to get anyone here to explain this to me. I even emailed SSBC (Stainless Steel Brakes Corporation) and asked them for some explanation, and I think I called also - but got no response. I was ready to buy something from them, but I guess they didn't feel like I was important enough to answer if their drum/disc or disc/disc application would work for drum/drum setups.

Nobody here has really told me what the difference is, so I went and looked it up and confirmed it with someone I believe knows brakes well while on the phone earlier today.

I don't think anyone really has a clue about brakes, upgrading to power brakes, boosters or master cylinders. If they do, they're pretty damned tightlipped about it, because I've been asking around these parts for almost 18 months now

[mbgmike]

Not really complicated

4 wheel power drums should use a metering valve (not same as prop) to help prevent nose dive, premature brake show wear, spongy brakes etc.

Disc frt and drum rear as stated earlier require a proportioning valve and or a later style combination valve

4 wheel dics obviously would have to use a combination valve

Hope this helps

[jaros44sr]

Shifty, let me put it this way. He has drums all the way around, I have factory discs up front of mine, we want to know if my 1/2 ton booster M/C will work on his truck? I don't want to ship this unit to Merry Old England and not have it work. Thanks guys for all your input, pls. help

[Brad]

This can get to be a rather confusing subject, but bottom line is make sure that you get the proportioning valve for a drum/drum if using drums or the propotioning valve from a disk/drum setup and I would stick with the year it came from rather mixing and matching different years although it can be done.

[mbgmike]

If using four wheel discs it is better to use a dual diaphragm booster. They require more pressure

[shifty]

What is difference between metering valve and combi valve?

[mbgmike]

Originally Posted by shifty

What is difference between metering valve and combi valve?

they are sort of the same thing but the proportioning valves are used to on the rear brakes of a disc/drum setup. just on the rear brakes.to prevent rear wheel lockup in SEVERE braking conditions

The metering valves are used on the front circuit allows the reare brakes to catch up with the fronts.

[shifty]

Well, in that case, I don't want the pressure riding on me.

As I understand it, and as others have said in here, the booster and MC seem to be the same, the big difference is whether it will need a combi valve, a metering valve or a proportioning valve. But, it's really next to impossible to get anyone to tell you that info here (I assume nobody really knows, which I find hard to believe )

[Brad]

The booster will work just fine.
The m/c may or may not work depending on what it looks like.
The pic below shows an original drum/drum m/c and a later model disc/drum or drum/drum m/c. The m/c's that came on '73 and later with the bigger front resevoir probably won't work for his application.

[shifty]

Just out of curiosity, what's the actual difference between the two that would allow it to work with one application, but not the other?

[mbgmike]

Originally Posted by shifty

Just out of curiosity, what's the actual difference between the two that would allow it to work with one application, but not the other?

drum brake mc's have residual valves inside disc do not and also a smaller bore than a disc mc
if you use a drum brake master cylinder on a disc brake setup you don't have enough volume applied to the brakes and they will drag because of the residual valve built into it.

drum brakes use less fluid than discs do.
e is
if you use the disc mc on a manual setup that doesn't work good either. the bore is too large and piston depth is too shallow to work for the drums.

[Brad]

Here's the part where I look really stupid.........drum roll please.................'I don't know, it's just what I've been told'.

Actually, I think it has something to do with the fact that the bigger resevoir puts more pressure on the front lines......er something like that, lol.

[mbgmike]

Originally Posted by Brad

Here's the part where I look really stupid.........drum roll please.................'I don't know, it's just what I've been told'.

Actually, I think it has something to do with the fact that the bigger resevoir puts more pressure on the front lines......er something like that, lol.

They require more volume is what it is

[shifty]

I've heard so many conflicting stories, I had to ask Thanks for being honest.

I ask because I am picking up a 1985 Fiero booster and a newer truck master cylinder that are mounted together on a bracket that will fit our trucks from what I understand, it will work.

I also saw that FirstGen used a newer truck or car master cylinder on his truck as well with no hacking and no problems.

I honestly think the master cylinder is just a resevoir, but I haven't looked at the internals. It seriously is starting to look like, to me, a lot of these boosters and master cylinders are pretty universal, as long as the post on the brake pedal is long enough to engage the thing properly.

It would be really cool if a brake specialist could jump in and clarify on this! (wink wink, nod nod, nudge nudge )

[shifty]

Brad - Pics are on this page:

http://home.comcast.net/~taylortsims/exhaust.html

Scroll down and you'll see the MC he was using on his truck. Definitely newer...

[Brad]

Jason, the pics are pretty dark but I see what's going on. That reminds me of what I did. For about 2 weeks I had just the m/c from a 1991 S-10(pd brake) on my truck using the prop valve from a 1977. It worked ok, but I really had to put my foot in it and I'd hate to have to rely on it during a panic stop. It was just the m/c without a booster. I think it would have been ok if I had a booster to go with it, but I didn't have that around. After that, I tried attaching it to a 1968 3/4T booster but the rod going to the m/c was too long and I gave up drilling a longer hole in the pushing end of the m/c. That put me in my last and final metamorphasis; using 3/4T brackets, booster and a 1977 m/c with the '77 prop valve. It stops very nicely- not too touchy, but just right. That's why I think it's important to use the prop valve from the same style and year as your m/c- whatever that is.

Sorry to hijack your thread Phil.

[Lippyp]

No problems, I'm learning all the time. I don't need to change the master cylinder as it works fine, all I want to do is slip a booster in behind it. I'll go and take a picture of whats on there now if that will help someone clarify what I can use.

[kbs71]

QUOTE: "Well, in that case, I don't want the pressure riding on me.

As I understand it, and as others have said in here, the booster and MC seem to be the same, the big difference is whether it will need a combi valve, a metering valve or a proportioning valve. But, it's really next to impossible to get anyone to tell you that info here (I assume nobody really knows, which I find hard to believe )"


Here's what I know from reading about prop valves, risidual valves and our combi valve along with M/C's and boosters.

Boosters come single or dual diaphram. The single basically takes vacume source(s) to help "boost" the pressure exerted on the M/C by having vac on the brake M/C side of the diaphram of the booster and ambient pressure on the brake pedal side of the booster. When depressing the pedal you reach a point when the booster opens allowing the vacume to assist in pushing the brake control rod from the booster to the M/C. A dual diaphram does the same thing only using two diaphrams of diffrent vacume pressures, thereby increasing the force exerted on the M/C rod, The dual system is used in either extream heavy duty applications or smaller diamater boosters.

On to the M/C's, the amount of line pressure exerted by the master cylinder depends on the "bore" of the cylinder which is measured as you look into where the rod end goes into it and presses on the piston. Bigger bore less PSI exerted. smaller bore more PSI exerted. The reservoirs depend on several items. Type of brake used, line length and line flex. The longer the line the more flex and the more area of the brake applicator (ie: caliper/# of pistons, vs. brake cylinder) will determine the size requirement of the reservoirs. More of all the above, larger reservoir. Now here where it looks contradicting because the larger reservior is for the front brakes, here's why. Our truck use a combination valve that has a residual and proportioning valve built in. The rear brake system has a lot less area to push due to the residual valve keeping the brake cylinder from returning all the fluid back to the M/C and less pressure is requires to exert the same stopping power to the drums due to the fact that their surface area is probably 10 times that of the front disc. The front reservior is larger due to the fact that brake fluid must return there when the pedal is released, because there needs to be more room between the pads and rotors to prevent squeal and drag. Remember there are no return springs in the calipers like on the rear brake brums keeping them away from the braking surfaces.

Residiual valves (used mostly in drum set ups) do just as it sounds, keeps a constant residual pressure on the brake wheel cylinder so it doesn't have to move as far, there by applying brake pressure before the non-residiual valved brakes can. They are usually either 7 PSI or 10 PSI depending where the brake M/C is located. They will help apply braking pressure slightly sooner to the rear wheels to prevent nose dive, and premature brake lockup. This will also keep the brake cylinder full with fluid so there is less brake pedal travel.

Prop valve or proportioning valve regulate how much pressure goes to which brakes. They do this by regulating the opening size for the fluid to that brake pair.

The combonation valves found on our trucks do the following. On the drum/drum and disc/drum trucks, they keep residual pressure (7 PSI) applied to the rear brake system so the rear brake are applied slightly sooner than the front to prevent nose dive and better brake actuation, there by equlizing braking pressures at the start of braking. It also acts as a proportional valve allowing more pressure to be applied to the fwd disc and less to the rear drums to prevent rear brake lockups. There is also a brake pressure switch internal of the valve that tells if the valve has failed. This is done by compairing brake pressures from both sides of the valve. If it is incorrect there is an internal piston that will move in one direction assisted by a spring, causing a ground to be completed and turning on the "Brake" light on the instrument panel.

Residual valves should be used in all rear drum applications to apply the rear brakes sooner, and keep proper pressure in the brake cylinder so it doesn't have to move as far during brake application.
Prop valves should be used in all applications to properly distribute braking pressures to prevent rear wheel lock up.
Most disc/disc combonations will need at the least a proportioning valve.

Thus the combonation valves found on our truck are specific for that brake set up for that model. Sure they will work on diffrent applications other than what they were made for. That's the beauty of working on older vehicles, you get to experiment to see what works best in your set up. It may be a crusty looking combonation valve off a C-60 or a old Impala. Or you may go and buy all new after market stuff and put at all together and make it work.
It comes down to what ever you want. Just remember you dealing with an application that's trying to stop a 2200 pound monster so what ever you do test it out going slowly and work your way up to hi-way and freeway driving. It's better to find out in your neighborhood or a back road that your front brakes are locking up and your rears arnt working at all, other than it is at 55 MPH during a panic stop.
Hope this helps.

[jaros44sr]

Thanks KBS, good read. I had to read it a couple of times for it to sink in. J

I really wasn't putting 'pressure' on any one, I just wanted to do right by Lippy

[shifty]

Hey kbs71, that was some of the best info I think I've ever read at this forum and it was very long overdue!

From reading that, it looks like, basically, you can swap any master cylinder with any booster, as long as the rod will reach properly. Although, if the booster is double-diaphragm, you can expect some more kick in the teeth