More braking power needed

[Higgins56]

I recommend Hawk HB646F.526 pads for the front discs. Put them on my 71 when I did the brakes last year. Definitely more agressive grip.

https://www.amazon.com/gp/product/B004MW5WC8/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Thanks for the hint !

 

[Higgins56]

Old pads of unknown quality and whether they were broken in correctly may be the problem. Glazed over pads don't work very well. Old, rusted rotors won't help any, either. If the rotors are within specs (thickness and run-out) they can be turned to give them a nice surface to break in new pads with good friction material.

That was a good point - altough they look tidy - who knows what they really are....

 

[tony-muscle]

Something is amiss here. 20 in at idle is a lot, what cam are you running? I am only getting around 11 - 12 in at idle with a 351c and I can lock up all fours no problem with 17x9 all around and stock brakes.  I do not think your issue is a lack of vacuum.

HI,

the cam is Mechanical Roller Comp Cams Extreme Energy 242/248 @0.050"

Heads are AFR Bullit

Intake is Edelbrock Performer RPM Airgap

I made  another test and  connected the Hella pump directly to the booster - yah - I found more brakes but did not lock up yet....

Interesting  was also to find out that the pressure switch  from Summit cuts the pressure at 14 inHg !!!!!! At this level the brake  pedal was stone hard....

This same look pressure switch seems to be offered in different  kits as well ?

Where to get a  switch  to adjust it till 24 inHg ?

I also added a Hella vacuum pump as yours in combination with a vacuum reservoir to my system.

Here is a brief description: https://www.7173mustangs.com/thread-muscletang-mod-project-thread-1971-m-mach-1?pid=340221#pid340221

I ended up using an adjustable vacuum switch from Superior (K058) (https://superiortransmission.com/product/superior-k058/).

I don't think it will get to 24, but 21-22 should be okay.

BTW, vacuum may not be your issue (or your only issue). I have been trying to get my brakes to lock up in the front and have not been successful. I am now working in my last resort replacing the last OEM component left in the system, which is the combination valve. This is my recent thread about it: https://www.7173mustangs.com/thread-front-brakes-not-locking-up

 

[Higgins56]

Something is amiss here. 20 in at idle is a lot, what cam are you running? I am only getting around 11 - 12 in at idle with a 351c and I can lock up all fours no problem with 17x9 all around and stock brakes.  I do not think your issue is a lack of vacuum.

HI,

the cam is Mechanical Roller Comp Cams Extreme Energy 242/248 @0.050"

Heads are AFR Bullit

Intake is Edelbrock Performer RPM Airgap

I made  another test and  connected the Hella pump directly to the booster - yah - I found more brakes but did not lock up yet....

Interesting  was also to find out that the pressure switch  from Summit cuts the pressure at 14 inHg !!!!!! At this level the brake  pedal was stone hard....

This same look pressure switch seems to be offered in different  kits as well ?

Where to get a  switch  to adjust it till 24 inHg ?

I also added a Hella vacuum pump as yours in combination with a vacuum reservoir to my system.

Here is a brief description: https://www.7173mustangs.com/thread-muscletang-mod-project-thread-1971-m-mach-1?pid=340221#pid340221

I ended up using an adjustable vacuum switch from Superior (K058) (https://superiortransmission.com/product/superior-k058/).

I don't think it will get to 24, but 21-22 should be okay.

BTW, vacuum may not be your issue (or your only issue). I have been trying to get my brakes to lock up in the front and have not been successful. I am now working in my last resort replacing the last OEM component left in the system, which is the combination valve. This is my recent thread about it: https://www.7173mustangs.com/thread-front-brakes-not-locking-up

Thanks Tony Muscle !

I found out that this  miserable switch is  in a way  adjustable but you have to  take the  switch apart out of the "T" and  adjust it by yourself  ( maybe not thought  by the manufacturer in the first place) but anyway I will  give it a try first.

What kind of reservoir you are using  for vacuum - there is not much place  where the original  "tin can " sits.... Can you send a photo ? ( [email protected] )

maybe I have to go through the  fron brakes as well - clean and check them - maybe renew this and that.... what front brakes you have - original?

 

[tony-muscle]

HI,

the cam is Mechanical Roller Comp Cams Extreme Energy 242/248 @0.050"

Heads are AFR Bullit

Intake is Edelbrock Performer RPM Airgap

I made  another test and  connected the Hella pump directly to the booster - yah - I found more brakes but did not lock up yet....

Interesting  was also to find out that the pressure switch  from Summit cuts the pressure at 14 inHg !!!!!! At this level the brake  pedal was stone hard....

This same look pressure switch seems to be offered in different  kits as well ?

Where to get a  switch  to adjust it till 24 inHg ?

I also added a Hella vacuum pump as yours in combination with a vacuum reservoir to my system.

Here is a brief description: https://www.7173mustangs.com/thread-muscletang-mod-project-thread-1971-m-mach-1?pid=340221#pid340221

I ended up using an adjustable vacuum switch from Superior (K058) (https://superiortransmission.com/product/superior-k058/).

I don't think it will get to 24, but 21-22 should be okay.

BTW, vacuum may not be your issue (or your only issue). I have been trying to get my brakes to lock up in the front and have not been successful. I am now working in my last resort replacing the last OEM component left in the system, which is the combination valve. This is my recent thread about it: https://www.7173mustangs.com/thread-front-brakes-not-locking-up

Thanks Tony Muscle !

I found out that this  miserable switch is  in a way  adjustable but you have to  take the  switch apart out of the "T" and  adjust it by yourself  ( maybe not thought  by the manufacturer in the first place) but anyway I will  give it a try first.

What kind of reservoir you are using  for vacuum - there is not much place  where the original  "tin can " sits.... Can you send a photo ? ( [email protected] )

maybe I have to go through the  fron brakes as well - clean and check them - maybe renew this and that.... what front brakes you have - original?

Which switch are you using. Mine adjust via a tiny screw on the vacuum port.

I am using a Jegs vacuum reservoir. I was able to fit it in the same spot as the original tin can. I also manage to fit the vacuum pump under the reservoir. It took some work due to the tight space but in this location it is hidden from view. I also have a sump fuel pump from my EFI in that corner so things are tight but partially hidden. I still need to start a thread showing the build but here are some pics.

Vacuum pump below brake line installed with custom brackets:



Vacuum canister. You can see the vacuum lines and the gauge. The A/C vacuum line connects to the same fitting where the gauge is. I got a vacuum tee and drilled and tapped a barb for the A/C line.

 

[Higgins56]

Thanks Tony Muscle !

i decided to open the pressure switch from its hose connection unit. This revealed a setting screw under the switch. Mine was set more or less half way and it showed 14 inHg at the gauge. I turned the set screw clockwise as far as it went to obtain the max. vacuum - which I did now. It is ab. 22 inHg ( pump gives 24 mmHg ) so it is OK now.

The switch code at Summit is SSB-28146-SW and a similar switch can be found from Comp Cams, too. This switch seems to be present at many kits as well for vacuum pump.

So the switch as it is can give any figures rather than the specified 18-22 inHg range, so it has to be calibrated after the purchase to be sure what it can deliver.

 

[Higgins56]

and finally when the vacuum was OK and the hose connected to the booster revealed something new.

This lower vacuum ment that the booster has to be in tip top condition - no leaks..... but in my case there is a tiny leak which means that the vacuum pump after reaching the desired level starts to start and stop in ab. 2-3 sec intervals which is not good.

The vacuum pump worked as planned till the booster check valve - all connections were tight but when the booster was connected to this the pump started working in intervals = never stops...

This means that I have to buy a new brake booster.

So at the moment I am driving the car getting the vacuum from the intake manifold. Surpriningly it makes a decent vacuum to brake.

There MIGHT be a question as well to go through the front disc brakes calipers and pads to be sure that they work as they should.

 

[Don C]

Is the first part of your last post missing?

Have you verified that the problem is the booster and not a connection, or even an internal leak in the pump?

 

[Higgins56]

Is the first part of your last post missing?

Have you verified that the problem is the booster and not a connection, or even an internal leak in the pump?

Hi Don,

up to the  check valve of the brake booster  all seems to be  OK now but  this lower vacuum revealed  a  tiny ?  leak in the booster - as I see it...

as the vacuum pump  dont stop but  runs in  ab 2-3 sec cycles....

If I take  the hose  out of the  booster check valve and close it with my finger the pump is dead still..... then I took also the  check valve  out of the booster and the same thing..... which leaves only the booster to be the guilty one..... but it works resonably well with the engine vacuum, so I can drive the car.

The booster is a 9"  basic  flat  booster..... I think I will order  one and use the same master cylinder which is new or would you prefer nevertheless to buy a combination  ready mounted ?

 

[Higgins56]

I also added a Hella vacuum pump as yours in combination with a vacuum reservoir to my system.

Here is a brief description: https://www.7173mustangs.com/thread-muscletang-mod-project-thread-1971-m-mach-1?pid=340221#pid340221

I ended up using an adjustable vacuum switch from Superior (K058) (https://superiortransmission.com/product/superior-k058/).

I don't think it will get to 24, but 21-22 should be okay.

BTW, vacuum may not be your issue (or your only issue). I have been trying to get my brakes to lock up in the front and have not been successful. I am now working in my last resort replacing the last OEM component left in the system, which is the combination valve. This is my recent thread about it: https://www.7173mustangs.com/thread-front-brakes-not-locking-up

Thanks Tony Muscle !

I found out that this  miserable switch is  in a way  adjustable but you have to  take the  switch apart out of the "T" and  adjust it by yourself  ( maybe not thought  by the manufacturer in the first place) but anyway I will  give it a try first.

What kind of reservoir you are using  for vacuum - there is not much place  where the original  "tin can " sits.... Can you send a photo ? ( [email protected] )

maybe I have to go through the  fron brakes as well - clean and check them - maybe renew this and that.... what front brakes you have - original?

Which switch are you using. Mine adjust via a tiny screw on the vacuum port.

I am using a Jegs vacuum reservoir. I was able to fit it in the same spot as the original tin can. I also manage to fit the vacuum pump under the reservoir. It took some work due to the tight space but in this location it is hidden from view. I also have a sump fuel pump from my EFI in that corner so things are tight but partially hidden. I still need to start a thread showing the build but here are some pics.

Vacuum pump below brake line installed with custom brackets:



Vacuum canister. You can see the vacuum lines and the gauge. The A/C vacuum line connects to the same fitting where the gauge is. I got a vacuum tee and drilled and tapped a barb for the A/C line.

 I am having my installation exactly in the same place.

I see you have  an AC compressor there where I have the  vacuum pump and at the moment I am using the original "tin Can" as the reservoir but might consider the same  one as you did.

 

[tony-muscle]

Thanks Tony Muscle !

I found out that this  miserable switch is  in a way  adjustable but you have to  take the  switch apart out of the "T" and  adjust it by yourself  ( maybe not thought  by the manufacturer in the first place) but anyway I will  give it a try first.

What kind of reservoir you are using  for vacuum - there is not much place  where the original  "tin can " sits.... Can you send a photo ? ( [email protected] )

maybe I have to go through the  fron brakes as well - clean and check them - maybe renew this and that.... what front brakes you have - original?

Which switch are you using. Mine adjust via a tiny screw on the vacuum port.

I am using a Jegs vacuum reservoir. I was able to fit it in the same spot as the original tin can. I also manage to fit the vacuum pump under the reservoir. It took some work due to the tight space but in this location it is hidden from view. I also have a sump fuel pump from my EFI in that corner so things are tight but partially hidden. I still need to start a thread showing the build but here are some pics.

Vacuum pump below brake line installed with custom brackets:



Vacuum canister. You can see the vacuum lines and the gauge. The A/C vacuum line connects to the same fitting where the gauge is. I got a vacuum tee and drilled and tapped a barb for the A/C line.

 I am having my installation exactly in the same place.

I see you have  an AC compressor there where I have the  vacuum pump and at the moment I am using the original "tin Can" as the reservoir but might consider the same  one as you did.

I am using the engine in combination with the pump as vacuum source so I have a check valve between the vacuum pump feed to the reservoir and the engine manifold. Under normal conditions the pump will produce more vacuum than the engine but if for some reason the pump fails I will still have the engine vacuum to help.

 

[Higgins56]

Is the first part of your last post missing?

Have you verified that the problem is the booster and not a connection, or even an internal leak in the pump?

Don,

I am now 99% sure that the booster is  somewhat leaking . I renewed the  check valve and the  rubber grommet - no change. The pump continues in tiny burst when connected to the  booster...

I have  noticed that there  are many offerings for a 9 " booster  ( four  bolts connection) but what would you recommend for the 71  Mach 1 with original front disc brakes ?

I want to be 100 % sure that it fits  the car  and the  newish master cylinder.

 

[tony-muscle]

I have one from LEED brakes: https://leedbrakes.com/i-21155650-9-inch-power-brake-booster-black.html

You may have mentioned this earlier, but did you try capping (with finger works) the hose to the booster to make sure the leak is not somewhere else? During my install I had one leak that was a nightmare and after a lot of troubleshooting I figured it was one of my customized metal fittings that had a cracked.

 

[Higgins56]

+1 on Don C's posts. Here are some easy tests. "Booster Function Test: Check pedal feel and vacuum booster function while test-driving the vehicle. With the engine off, apply the brake pedal repeatedly with medium pressure until the booster reserve is depleted. At least two brake applications should have a power-assisted feel before the pedal hardens noticeably. If the pedal feels hard immediately, or after only one brake application, it may indicate a vacuum leak or a low level of engine vacuum. Inspect the vacuum hose to the booster for kinks, cracks or other damage. Check vacuum at idle with a vacuum gauge. 

https://s3.amazonaws.com/assets.knowyourparts.com/app/uploads/2016/09/automotive-vacuum-booster.jpg[/img]To test booster function once the reserve is depleted, hold moderate pressure on the brake pedal and start the engine. If the booster is working properly, the pedal will drop slightly."

Also, 20 in/hg is a lot of manifold vacuum for a modified 429 engine to generate at idle. Is idle speed high, or timing too far advanced, do you have another vacuum gauge to compare results? I currently have a 1969 Cougar and a 1972 Mach 1 that have aggressive cams and make 11.5-12.0 in/hg and still run the booster although these numbers are near the edge of not working with the OEM single diaphragm booster. Chuck

Hi Don,

well......there was a small leak  in the booster so I replaced it with a Leeds  Brakes 9" booster for 71 Mach 1. When changing the booster I noticed that  the old booster was  a 11" booster - maybe  for a bigger Ford - anyway the  bolt pattern was the same. I checked the  dimension  for the  rods for the pedal and the MC ( 145 mm / 25 mm) and the MC  cylinder diamameter  and stroke I checked , too ( 12 mm / 35 mm ) which was the same  as the old one  I replaced a year ago.

I also decided to buy new brake pads ( C-Tek Metallic pads = standard pads ?) . This change was important as the old pads  - altough hardly used - > 30 years old ? were about to crack and partly loose ( riveted pads !) so now this is OK.

After  priming the air out from the  MC connection I made  the test ride: First the  brakes did not  seem to be much better than before  but when I made  more stops they start to bite better. After  ab. 5 miles I was back at the garage and  noticed the smell from the front pads and saw that the  rotors were dark blue....= very hot !

I jacked up the front  and turned the front wheels by hand . They  could be turned without too much  effort but  my question now is: How much force  is accepted to use when  deciding what is too much when turn the wheel by hand ? 

If the  pads are too close what would you check first ?

The  new vacuum system works with the new booster otherwise fine.

 

[Don C]

Were the rotors new, or freshly machined for a break-in surface? If not they should have been scuffed. New pads on used rotors that were not prepared cause the pads to glaze, resulting in high temperatures and poor braking.

 

[Bentworker]

Did you check pushrod length when you swapped your brake booster?

The reason I ask is because if the pushrod is too long it can result in dragging brakes.

See this neat little brake setup paper from Jegs https://www.jegs.com/installationinstructions/500/555/555-631010-116.pdf

 

[Fabrice]

[When changing the booster I noticed that the old booster was a 11" booster - maybe for a bigger Ford ]

Same here, I still have the old 71 11 inch that I might attempt to restore one (far far away) day, for now, I had to do with the 9 inch as the shipping costs to Booster Dewey and back + repair would have made it idiotic. They are indeed identical aside the diameter. More space is this crowded corner isn't that bad

[How much force is accepted to use when deciding what is too much when turn the wheel by hand ? ]

Practically zero. tho depends on wheel weight to get started. but once it turns, it should stay turning on its own for a few, only noise would be may be a tad of friction on new pads but not really succeeding on stopping the wheel.

Considering your question and the dark blue tint, looks like the pads are always under pressure, never at rest. Chances are now also high the rotors are no longer flat and needs be turned or replaced.

 

[Robsweden]

Check the valve in the distribuiton block, If it stuck your front brakes will drag.