How do you test Power Brake Booster

[ray1970 88]

LIFT ME UP...

[1969_Mach1 333]

I'm guessing your joking about that solid roller cam being more suitable.  It has longer durations, shorter lobe separation angle, more valve overlap, and the valve lift can be measured with a yard stick.  The first cam you show is slightly better for power brake operation than what is currently in the motor.

[prayers1 153]

Today I hooked a Vac gauge to the manifold vac port and drove the car. I immediately felt like I had NO brakes, similar to the feel of manual brakes.

I was quite surprised since I had the belief that the pwr brakes felt like manual brakes, but now driving w/o vac to the booster I can easily feel the difference.

After I reconnect the manifold Vac to the inline reserve tank I felt  power brakes but not the strongest pedal as our newer cars.

Cruising with the pedal down I was getting 17-18" of vac.

[1969_Mach1 333]

Without a vacuum source to the brake booster is usually worse than manual brakes.  It sounds like the booster is working some.  I was hoping you would have kept the brake booster connected while the vacuum gauge was attached.  Because now, you don't know if the power assist was better during times of 17"-18" of vacuum.

[ray1970 88]

The first cam card is from my 408 street car... 12lb of vacuum

I think the brakes work very well (front bumpers still there)

Cam card NO.2 from the 408 mud truck. Never put a meter on it

I'm thinking its very LOW..on vacuum..

My old booster worked a lot like P1s description of his new one.?

That's why I put a new one on mine and life was good .. At 12lbs

[barnett468 418]

12 hours ago, prayers1 said:

Today I hooked a Vac gauge to the manifold vac port and drove the car. I immediately felt like I had NO brakes, similar to the feel of manual brakes.

Cruising with the pedal down I was getting 17-18" of vac.

the vacuum gauge should be connected to the full time vacuum port on the carb and should have zero affect on the brakes.

17-18 at cruising speed means you have a huge cam. a newer stock type car is around 28. the vacuum will go up some when you release the gas pedal which is when the brakes will work their best.

 

[ray1970 88]

At the risk of compering mine to yours for they are 2 different set ups but not really..

Down the road  mine is 17-18lb       21lb if I let out at road speed --55mph

I want a bigger cam....what I have I don't see it being to big for a 408 with rollers..

idles smooth with some lump to it (that shaker needs to shake)      Runs good in town.

I find it a bit tame. And yes it will burn the tires without asking..

Stops better than my minivan or f250 ford. they could be better..

[ray1970 88]

P1 I think your system is to new for this..

Had a booster fill up with break fluid at one time do to a bad MC

It had that same feeling.   

[prayers1 153]

As some of you may have already read my previous post about the rear drums not stopping, when I forcefully turned the tire with someone applying the brake pedal.

Therefore at this point, I am combining the 2 threads which continues as follows:

I picked up a Mityvac brake bleeder and did both rear drums. I was not getting a solid steady stream of fluid, it had more bubbles in it as I that it should, but it did vacuum out the MC 2x, so I know the fluid was traveling. I looked all over and could not find any source of a leak in fact the pressure held still on the Mityvac even when it was fully pumped.

I then adjusted the park brake and readjusted the rear brakes. I had the wife apply the brakes while the car was on jack stands, in neutral and running, The left rear was tight but the RR still could be turned and inch of so, so I adjusted the brake again and it held. It was easier to turn the wheel in reverse, then forwards. I feel I may have it adjusted too tight, it's really hard to tell because I always feel friction as I spin the tire to check for tightness. I took the RR apart and applied some anti-seize to the threads of the brake star, put it all together and it felt the same as before, in fact both sides feel tight as I try to free spin it.

Next, I hooked the Vacuum gauge to the brake system in-line with the reserve canister, I was getting around 14" of vac at idle. Cruising it was 19 and wot 22.

The brakes are stopping the car and the front nose dives but not the same as our newer cars. I slammed on the brakes and had the right front lock up a little.

At this point I do not know how much the rears are stopping the car. The car does stop and I feel the somewhat feeling of pwr asst but I wonder how it would stop on a panic brake or stopping at high speeds. I do want to take the car to the track and I surely want to be able to stop after hitting 100 mph.

Any suggestion would be greatly appreciated. Thank you

[1969_Mach1 333]

To adjust the rear brakes, first make certain the emergency brake is fully releasing so that the top of the shoes are firmly up against the pin at the top of the backing plate.  Then simply rotate the adjuster wheel until there is very very light rubbing on the brake drum.  After that, put the car in reverse, back up, doesn't have to be fast, apply the brakes and let the automatic adjusting feature do the final adjustments.  Then go forward a little and stop, and repeat the procedure of backing up and applying the brakes.  You will have to do that a few times.  If the brakes were very far out of adjustment you will feel the brake pedal come up some as the self adjusters adjust the brakes.

After this is complete, adjust the emergency brake.  Be cautious not to go too tight on the emergency brake.  When completed, with the emergency brake disengaged, the brake shoes need to return to the pin at the top of the backing plate.

FYI, be certain the brake shoes are installed correctly, the shoe with the longer lining goes on the rearward end of the car.

If you manually adjust the brakes too tight they cannot "duo-servo" operate correctly.  You've probably noticed you can grab the brake shoe assembly at the bottom and move them front to back.  How they operate is when the brakes are applied, the wheel cylinder pushes the top of the shoes out into the drum.  The rotating drum will rotate the brake shoes a little and further wedge the rear shoe into the drum.  Hence the name "duo-servo", (some say dual servo) first  is hydraulic action from the wheel cylinder and second is a mechanical wedging action from the rotating drum. 

[Rsanter 152]

I don’t really want to compair mine to yours...but I will describe mine

i am using a booster from tuff stuff. It is a small booster but basically the same one used on the boss429 cars. Just not concourse correct.

my engine is modified but not as much as yours. 

i can use my big toe to operate the brakes and if you are not buckled up I can put your nose to the windshield.

 

some things that come to mind, you need to sort out the thoughts....

Are your front calipers on correctly? If you swap the left to right they will fit and they will work. But they will trap a little air in the caliper that will reduce your braking.

have you removed the bleeder screw and installed a pressure guage in its place to see what pressures you are getting at each corner?

i do not understand the vac readings, are you really getting more vac at WOT? I always thought that’s when your loose or drop vac?

a vac resivoir is used to store vacvume, your vac will go up and down. When the vac is up it should store in the can, when it’s down you have it stored in the can to use. Do you have a check valve between the engine and the can? You should have one. Then there is another one at the hose fitting to the booster.

is the vac can you installed big enough? Have you seen the size vac can they installed on the Cougars because of all the vac accessories they have on that car? Have you seen the size vac can they use just going to the AC system vac motors? Just reference.

some of the newer small diesel cars (VW I think) use an alternator that has a vac pump built onto the back of it, could be an option .

 

 

[LoneWolf2U 136]

Your lack of braking power to me indicates there is not enough pressure to the wheels.

Without checking the booster to master rod for proper clearance to plunger, the stroke from your brake petal is not applying full pressure to the wheels.

[Rsanter 152]

Oh, and one of the tricks I have used in the past to see if a booster is good on a non-running car

run a hose from a running car connected to the booster you want to test.

you could try this with your car and then run from another car and see if there is any difference in feel

[prayers1 153]

Rsanter- I'm using the Summit Racing® Vacuum Reservoirs SUM-G1464B, it measures 5"x 6 3/4", it doesn't list its volume, but I believe it to be big enough or bigger than the Cougar one.
What kind of brake system are you using, Stock or Aftermarket. I don't think its possible to switch calipers from left to right and vise versa.

Mach1Rider- What your saying might be possible but for now It will have o wait towards the end of Fall, because I need to lift the motor to get the valve Cover off and right now I'd rather try something else while I can still drive the car.

1969_Mach1- I will try your brake adjustment as I had my parking brake adjusted somewhat tight when I did the manual brake adjustment. I didn't know your procedure and I've been doing my brakes for years. It does make a lot of sense with the top of the park brake loose. First chance I get I will do it and I thought also to disconnect the driveshaft when adjusting the drums cause I feel the transmission is also causing friction or drag on the free spinning of the tires.

 

[larryc94 38]

10 hours ago, prayers1 said:

 I don't think its possible to switch calipers from left to right and vise versa.

Oh they switch very well, just don't work well when on the wrong sides

 

 

[prayers1 153]

Larry- How do you know which is right or left?

[det0326 179]

If on the wrong side the bleeder valve would be toward the bottom causing an air pocket at the top that would probably be trapped and not bleed out. I believe you said your pedal was firm tho so I doubt that this is your problem.  I think you have 2 problems not enough vacuum and a proportional valve not functioning properly.

[prayers1 153]

OK, THANKS! I thought I was losing my mind.

I've been doing brakes for years, now it feels like I have to retrain myself from bad habits.

What I'm trying to do now is to make sure the drums are properly adjusted, before tackling the port valve or depth of the booster pin.

I was having a hard time determining if the drums were causing the resistance from the adjustment or the trans. I felt the drums were adjusted too tight, the RH  I had to back off the star a lot to get the drum off and the LH the drum just pulled off. It sounds weird but I believed the shoes were rubbing as I spun the tire or it may have been the resistance from the drivetrian who knows!!!

I felt there was too much drag in neutral, so I just took the driveshaft off. Now as I spin the rear at the axle, I still feel tightness from the rear. It was rebuilt about a year ago.

I had the park brake adjusted to the point that it would only take a few inches to push down on the ER brake to lock up. As I look at the top pin the ER shoe is still against the pin.

[larryc94 38]

8 hours ago, prayers1 said:

Larry- How do you know which is right or left?

The bleeders have to point towards the back of the car.  If they point up they are wrong

[prayers1 153]

Thanks for the pic Larry, you really had me thinking. Mine are on right.

Its raining at the time so I can't go for a test drive, but I loosen the parking brake all the way and re-adjusted the drums w/o the driveshaft attached. There must be some tightness in the rear cause the wheel still has residence to spin but not as bad as when the driveshaft was hooked up. It will spin one full revolution if i spin it hard but I hear metal rubber, the same sound when you adjust the brakes and this time it had a lot of slack on the star adjuster.  I noticed when spinning the tire that there was a quite spot every revolution on each side somewhat of an oblong rotation, I do not have an oblong problem with the pads or drums.

All the above makes it hard to tell if the pads are adjusted, so for now I think I have it close enough and will do the back up adjustment per 1969_Mach1 suggestion.

All thoughts are welcome!

 

[Rsanter 152]

On 10/3/2017 at 7:16 PM, prayers1 said:

Rsanter- I'm using the Summit Racing® Vacuum Reservoirs SUM-G1464B, it measures 5"x 6 3/4", it doesn't list its volume, but I believe it to be big enough or bigger than the Cougar one.
What kind of brake system are you using, Stock or Aftermarket. I don't think its possible to switch calipers from left to right and vise versa

 

On 10/3/2017 at 7:16 PM, prayers1 said:

 

Stock front disc brakes, late model SVO/Lincoln LSC rear disc brakes

stock dist block with an adjustable prop valve

Tuff stuff power booster. This is the same booster used on the boss429 cars but not concourse correct.

willwood master cylinder, same bore size as stock. I used this one for the looks and for the lack of a residual valve for the rear brakes.

all new metal brake lines and hoses

 

yes you can swap the calipers left to right and they bolt on and work. The bleeder valve need some to be horizontal

[Brian Conway 264]

14 minutes ago, Rsanter said:

 

Stock front disc brakes, late model SVO/Lincoln LSC rear disc brakes

stock dist block with an adjustable prop valve

Tuff stuff power booster. This is the same booster used on the boss429 cars but not concourse correct.

willwood master cylinder, same bore size as stock. I used this one for the looks and for the lack of a residual valve for the rear brakes.

all new metal brake lines and hoses

 

yes you can swap the calipers left to right and they bolt on and work. The bleeder valve need some to be horizontal

...and the bleeders point to the rear wheels.

[Rsanter 152]

On 10/5/2017 at 4:20 PM, Brian Conway said:

...and the bleeders point to the rear wheels.

Yes