'65 KH disc brake problems

[Allan S]

Hi Guys,

I've fitted the original-style KH 4 pot calipers and discs (brand new). I'm running an aftermarket 7" booster and master:

http://nelcohotrods.com/products/1964-66-mustang-chrome-power-7-booster-master-cylinder-for-automatic-trans

Original rear drums (a little bit of take-up as I haven't fitted the residual pressure valve to the rear circuit yet), all new.

I've got consistent 13"hg at idle in gear (Mild cam 289 4V, c4 auto, nothing ridiculous).

I've Bled both circuits numerous times (starting with the furthest nipple), but it still feels like air in the system. No leaks anywhere.

I've fitted the Scott Drake pedal pivot kit to reduce pedal travel.

Pedal travel is good, but EXTREMELY soft until the very end of it's travel. Initial bite is good (almost a shock, as the pedal is so light), but not great, but doesn't improve with more pedal force. After that initial bite, I can stand both feet on the pedal and the car WILL NOT lock up, and won't brake any better that that initial bite.

It's o.k for normal driving, but a bit scary in traffic. Emergency braking is not something it's capable of.

Questions:

1. Have I got enough vacuum? Do I need a vaccum pump or tank, or is there something wrong with my engine, only producing 13"hg?
2. Will the take-up in the rear make much difference once I get rid of it?
3. Is there something else altogether I haven't thought of?

Cheers,

Al.

[barnett468]

.
ok, holy crap.

yes, if you can not lock the brakes up, i would not drive it.

you should have more than 13 hg with a mild cam up to maybe a comp cams xe262h.

the residual valve will have absolutely no affect on the brakes guaranteed.

i looked at the photo and that smells like some chinese made parts to me.

with your system with the booster, ideally, you should have around 75 mm of pedal travel until the pedal gets rock hard and it should require moderate/firm pressure on the pedal to stop but it should not require a lot of pressure . . if your pedal travels 100 mm, it should stop with fairly light effort.


1. remove the vacuum hose to your distributor and plug it.

2. loosen the distributor bolt 1/8th of a turn.

3. check and post the timing at idle.

4. with the engine idling, rotate the distributor clockwise until the timing is 4 more degrees advanced and listen to see if the rpm increases . . if it does, AND the engine still runs smoothly, leave the timing there, then reduce the idle speed to normal and check engine vacuum.

5. set both fuel mix screws until you reach the highest/smoothest idle, then reset idle speed and check engine vacuum.

6. remove the master and check the play between the booster rod and the master piston . . this is friggen hard to measure without proper tools but it MUST be done . . this clearance should be around .015" or around .3 mm.

7. sit in the car with the engine off and pump the brake pedal and tell us if it pumps up.

8. remove and plug the vacuum to the booster then try the brakes to make sure it is working . . if its working, reconnect it

9. drive at 50 kph, then put the car in second gear, remove your foot from the gas, and mash the brake pedal and tell us what happens.

10. pull the emergency brake out until it stops then let it in 50 mm and see if the brakes improve or pedal travel changes . . do not drive over 50 kph or farther than 1 kilometer like this.


please  answer ALL of these questions one at a time.

how far does the pedal travel until it stops moving towards the floor?

how far away from the floor is the pedal once it stops moving?

how far from the floor is the pedal without your foot on it ie, is it stick height or closer to the floor than stock?

what brake pads and shoes are they?

are they new?

did you turn the drums and rotors?

do the rears or fronts ever lock up and if so which ones do?

what is the size of the master cylinder piston?

what type of brake fluid is it?

exactly which cam is it or what are the specs?

do any of your brake lines from the master to the junction box have a loop in them?

are any of your brake lines higher then the middle of the master cylinder?

do you have a proportioning valve?

what did the booster and master cost you on ozzie dollars?
.

[boofhead]

There is not much more to add though if your chasing air in the system then a test you can do
is to get some clamps and use them to clamp the flexible (rubber) lines used in the brake lines.
You need three clamps, two at the front near the disks, and one at the rear just above the diff left side.

The push the brakes - it should be almost rock solid - if not then the problem is not in the bleeding of the lines (or it was so badly done you have air in the master cylinder). If it is rock solid then you pull the rear clamp off first and try again - slightly less rock solid - if more then slightly then the rear might be out of adjustment or need more bleeding - go and bleed it. Then the left front test again, then the right front test again. You will quickly get an idea where the air (if any) is likely located.

[scollist]

Is the master new? (you didn't say). I'm definitely no expert, but if it is new and wasn't bench bled then could that be the problem?

[Allan S]

Thanks Mate,

Won't get a chance to do most of that until Sunday, but here are the answers I know (as I've tried most of this in the testing and tuning process)

I looked at the photo and that smells like some chinese made parts to me. I'm pretty sure they're MBM parts, made in the USA (North Carolina, not that that's much better than China!)

1. remove the vacuum hose to your distributor and plug it. Will do ASAP and report back

2. loosen the distributor bolt 1/8th of a turn. Will do ASAP and report back

3. check and post the timing at idle. Approx 10-12 BTDC (markings not so clear any more, I set it there deliberately it just pings a touch carrying 4 people and luggage if I flatten it up a steep hill, so I can't really go any more)

4. rotate the distributor clockwise until the timing is 4 more degrees advanced and listen to see if the rpm increases . . if it does, AND the engine still runs smoothly, leave the timing there, then reduce the idle speed to normal and check engine vacuum. Didn't advance it further because of the pinging, but at the current setting, the idle screw is right out and idle is normal (650rpm-ish).

5. set both fuel mix screws until you reach the highest/smoothest idle, then reset idle speed and check engine vacuum. This is how I got it to 13"hg in the first place, it was about 11-12 before I did that, and I couldn't get it any higher while tuning. Car was idling at 1100 at the time, will check again now I've got it idling at 650.

6. remove the master and check the play between the booster rod and the master piston . . this is friggen hard to measure without proper tools but it MUST be done . . this clearance should be around .015" or around .3 mm. When installing, I adjusted this. I couldn't get it precise (not the right tools), bit it doesn't quite touch until you hit the pedal. it's definitely less than about .5mm, but not touching at all.

7. sit in the car with the engine off and pump the brake pedal and tell us if it pumps up. Will do ASAP and report back

8. remove and plug the vacuum to the booster then try the brakes to make sure it is working . . if its working, reconnect it Will do ASAP and report back

9. drive at 50 kph, then put the car in second gear, remove your foot from the gas, and mash the brake pedal and tell us what happens. Will do ASAP and report back

10. pull the emergency brake out until it stops then let it in 50 mm and see if the brakes improve or pedal travel changes . . do not drive over 50 kph or farther than 1 kilometer like this. Will do ASAP and report back


please  answer ALL of these questions one at a time.

how far does the pedal travel until it stops moving towards the floor? Will measure ASAP and report back

how far away from the floor is the pedal once it stops moving? About 20mm

how far from the floor is the pedal without your foot on it ie, is it stick height or closer to the floor than stock? Will measure ASAP and report back

what brake pads and shoes are they? Front - The ones that came with the SSBC caliper kit Rear- not sure, a mate got them in the US, from NPD, I believe.

are they new? Yes

did you turn the drums and rotors? Drums - Yes, Discs - No (New RDA discs with the 'bedding in' coating)

do the rears or fronts ever lock up and if so which ones do? None at the moment. Will try once I've done the other stuff you mention and report back

what is the size of the master cylinder piston? Not 100% sure, I didn't measure, the company makes 1" and 1 1/8" bore, but I'm not sure which one he supplied. I'll ask.

what type of brake fluid is it? Castrol Dot 4 protector series

exactly which cam is it or what are the specs? Don't know, engine builder can't remember exactly. He thinks it's on old school equivalent of about a stage 2, whatever that means.

do any of your brake lines from the master to the junction box have a loop in them? No

are any of your brake lines higher then the middle of the master cylinder? Without checking (I'm at work), I'm fairly certain they're not

do you have a proportioning valve? No, I have an adjustable restrictor valve on the rear circuit to prevent rear lockups, but it is fully opened

what did the booster and master cost you on ozzie dollars? About $300 plus freight. (Aussie dollar was about even with US at the time)

[Allan S]

Is the master new? (you didn't say). I'm definitely no expert, but if it is new and wasn't bench bled then could that be the problem?

Master was new. I didn't bench bleed it,as the whole system was new, so I bled it as a whole.

[Allan S]

There is not much more to add though if your chasing air in the system then a test you can do
is to get some clamps and use them to clamp the flexible (rubber) lines used in the brake lines.
You need three clamps, two at the front near the disks, and one at the rear just above the diff left side.

The push the brakes - it should be almost rock solid - if not then the problem is not in the bleeding of the lines (or it was so badly done you have air in the master cylinder). If it is rock solid then you pull the rear clamp off first and try again - slightly less rock solid - if more then slightly then the rear might be out of adjustment or need more bleeding - go and bleed it. Then the left front test again, then the right front test again. You will quickly get an idea where the air (if any) is likely located.

This is a great idea, I will try this also. Cheers!

[barnett468]

.
ok

you have kelsey hays calipers from ssbc?


the master should be bench bled

the brakes should stop decently and lock up with either of the master cyls so it may be air and/or adjustment.

you can gravity one wheel at a time for 2 minutes . . just remove the m/c cap and open the valve on one wheel at a time . . make sure the master doesn't go low.


less than .5 mm but not touching is fine.

you absolutely must do the timing test . . do not worry about the pinging, i can fox that by reducing your mechanical vacuum or delaying it, besides the pinging may be caused by the vacuum advance . . drive it without the vac adv and see if it pings.

your idle timing needs to be with the distributor vac disconnected . . when connected it must go to ported vacuum not manifold vac . . it may also be adding too much vac so you might need an adjustable unit . . you do not need it so just plug it until further notice.

the pedal is too close to the floor . . needs to stop at least 2 inches above the floor.

you should not use a restrictor valve.
.

[GLENN 70]

Sounds like air in the system . Some brake calipers have a left and a right and if put on the wrong way won't bleed up ,not saying yours are that type . If the master cyl piston is a 1  1/8 inch it will have a hard pedal and need a lot of pressure to work . A 1 inch will work with less foot pressure .  You might have to look at the push rod between the master cyl and brake booster ,that its set at the right length .

[scollist]

Master was new. I didn't bench bleed it,as the whole system was new, so I bled it as a whole.

the master should be bench bled

My understanding is that a new master must be bench bled, even if you are bleeding the whole system later. Now that it is on the car that will be a lot harder, but I believe it can be done. You'll have to ask people better than me on how to do it.

[shaunp]

Its very common complaint with these kits, they slow up but wont lock, I have never had a look at one that does it, but I suspect the master cylinders are the wrong size or the boosters are crap. EBC pads make them better but dont fix them.

[Allan S]

Ok Barnett,

Had a crack at a few of the things you suggested this afternoon:

1. remove the vacuum hose to your distributor and plug it. Done

2. loosen the distributor bolt 1/8th of a turn. Done

3. check and post the timing at idle. Approx 10-12 BTDC

4. rotate the distributor clockwise until the timing is 4 more degrees advanced and listen to see if the rpm increases . . if it does, AND the engine still runs smoothly, leave the timing there, then reduce the idle speed to normal and check engine vacuum. Did this, increased revs and ran smoother (Except for the very occasional "flutter" it has developed in the last month or so, I suspect an issue with the pertronix using the original resistance wire). However, idle screw is fully out, cannot reduce the idle back to normal. RPM is about 850 now (idle, park). vacuum at this is about 19"hg. proper vacuum test is at idle in drive, rpm at this drops to about 700, vacuum about 15"hg. Certainly an improvement, thanks. Not sure about the pinging at this point, haven't done a road test. I have a few ideas on how to combat that, though (Nulon, 12v high performance coil, etc).


7. sit in the car with the engine off and pump the brake pedal and tell us if it pumps up. It does, but not as much as I thought it would.

8. remove and plug the vacuum to the booster then try the brakes to make sure it is working . . if its working, reconnect it. It is working, but the pedal loses all feel with it connected. am I better off trying to drive the car without the booster connected and see how the pedal feels? It feels a heap better idling in the shed...


how far does the pedal travel until it stops moving towards the floor? about 70mm (see below)

how far away from the floor is the pedal once it stops moving? Wow! it's amazing how wrong I was! it's actually 70mm of the carpet, only looks about 20mm from drivers point of view, but when you measure it....

how far from the floor is the pedal without your foot on it ie, is it stick height or closer to the floor than stock? 140mm off carpet (about 35mm higher than loud pedal, feels nice & natural, was about 3" higher before fitting the pedal pivot kit!!)


Vac advance is definitely ported (brand new 570 street avenger and all lines hooked up exactly as per manual)

are any of your brake lines higher then the middle of the master cylinder? Checked, definitely not.

[Allan S]

"8. remove and plug the vacuum to the booster then try the brakes to make sure it is working . . if its working, reconnect it. It is working, but the pedal loses all feel with it connected. am I better off trying to drive the car without the booster connected and see how the pedal feels? It feels a heap better idling in the shed..."


The reason I suggest this is that I was told originally, you couldn't get these brakes boosted on a '65, the options were apparently manual drums, power drums or manual discs. Is this true?

Just not sure what effect the disconnected booster will have sitting there between the pedal & the master?

[Allan S]

Its very common complaint with these kits, they slow up but wont lock, I have never had a look at one that does it, but I suspect the master cylinders are the wrong size or the boosters are crap. EBC pads make them better but dont fix them.

When you say "these kits" do you refer to the callipers, discs and pads (SSBC), or the master/booster combo (MBM)?

Cheers,

Al.

[barnett468]

.
ok xlnt . . back in a minute.

exactly what do you mean by loud pedal?

what do you mean the pedal looses feel with the booster connected . . does it go to the floor and bottom out on the floor?


forget about the pinging . . i will fix it if it pings . . i have done this a zillion times.

you have an air leak or a carb problem . . your car should die when the screw is all the way out.


1. while idling, remove the pcv valve and plug it and tell us how much the idle drops . . leave it plugged with masking tape irregardless.

2. plug the line to the brake booster . . if the rpm drops, it has a leak.

3. remove the throttle rod and see if you can back the screw out more to reduce idle
once the car is warm, turn it off for exactly 5 minutes then try to restart it and tell us if it turns over slower than before you changed the timing.

4. spray flammable carb cleaner with the long nozzle gently around the carb base and hose fittings on the carb and around the intake at the head.

5. the pedal pump test needs to be done after the car has sat for maybe one hour and the fitting must be remived from the vacuum booster . . if it pumps up st all it has air.

6. yes drive the car less than 1k with the booster disconnected.,

7. pull the e brakes like i said and drive it with the booster connected.

[GLENN 70]

Was the master cyl and booster together in the kit or did you have to put them together . Did you adjust the rod between them . It's a low pedal and I think it still has air in the system . Is it a 1 inch master cylinder and is it an adjustable push brake rod from master cyl to booster .

[Allan S]

.
ok xlnt . . back in a minute.

exactly what do you mean by loud pedal? accelerator pedal. You can't slide your right foot from the go pedal to the stop pedal, you have to lift it about 35mm. this feels natural, so I think this is fairly normal?

forget about the pinging . . i will fix it if it pings . . i have done this a zillion times.

you have an air leak or a carb problem . . your car should die when the screw is all the way out. I am talking about the idle speed screw, not the mixtures. Maybe the jets are too big?

1. while idling, remove the pcv valve and plug it and tell us how much the idle drops . . leave it plugged with masking tape irregardless.  Doesn't vary

2. plug the line to the brake booster . . if the rpm drops, it has a leak. Doesn't vary

3. remove the throttle rod and see if you can back the screw out more to reduce idle
once the car is warm, turn it off for exactly 5 minutes then try to restart it and tell us if it turns over slower than before you changed the timing. Kicks first go, but throttle rod removal made no difference, the the only affect the screw has is if I turn it in a bit, it does nothing for about a half turn, then starts increasing RPM.

4. spray flammable carb cleaner with the long nozzle gently around the carb base and hose fittings on the carb and around the intake at the head.  Nothing happens, idles along consistently.

[Allan S]

Sounds more and more like the masters coming out for a bench bleed.

I'll try the road test stuff tomorrow. I really appreciate all your help, Barnett and guys. Been up since 1, better get a kip in...

I'll post my other progress tomorrow or Thursday.

Thanks,

Al.

[barnett468]

.
ok based on your info, something is keeping the front or the rear butterflies in the carb from closing.

there is a small screw on the left rear of the carb, this is the stop for the secondaries . . turn it in 1 turn so it closes the secondaries more . . i forgot which way that is.

[barnett468]

Sounds more and more like the masters coming out for a bench bleed.

I'll try the road test stuff tomorrow. I really appreciate all your help, Barnett and guys. Been up since 1, better get a kip in...

I'll post my other progress tomorrow or Thursday.

Thanks,

Al.

i would do the other tests first . . it does not sound like you have much if any air in the lines but we need more info.

[barnett468]

.
ok, it doesnt look like those cheap bastards use a screw to close the secondaries . . looks like they have a tab bent over on the bottom of the carb in the top left of this photo to stop them.

look inside the carb at the butterflies, the ones that are the farthest open are the ones you need to close more . . if it is the rear, bend the tab downward slightly unless there is a screw adjustment there . . if  there is, turn it out 1 turn.

if the fronts need to close more, make sure the cam on the cloke is loose . . the choke high idle screw may be holding it open slightly.

if nothing is holding the fronts open, you mist remove the carb and loosen the butterfly screws until you can move the plates in the rod . . spray wd40 on them then close and open the throttle twice then hold the throttle closed and tighten the screws.

as i mentioned, you absolutely must be able to kill the engine with the idle screw . . this is all interrelated.

[barnett468]

.
ok, we need all the other test results but based on the info so far . . if there is no air in the system, you can raise your pedal up 20 mm if your brake rod is adjustable, then if your master is 1 1/8", you can buy a 1" one . . this will make the pedal travel around 25 mm more than it does now and it will lock your brakes up.

if there is air in the system it might be ok, if it is not, you can still install a smaller master.

[PET-289]

The KH caliper is hard to bleed because of the cross over tube that links both sides of the piston.
Dont worry about bench bleeding the master cylinder.
Buy yourself one of these power bleeders and do it yourself.
http://www.ebay.com.au/itm/Motive-Holden-Ford-Billet-Rectangle-Bleeder-1-Person-Brake-Bleeding-Tool-/111596274339

[MACH_ONE]

Interesting read...I would of thought to bench bleed the master...also Im not sure on the KH but is it possible to have the bleeder screws on the bottom instead of the top again Im not sure never had KH.

[shaunp]

When you say "these kits" do you refer to the callipers, discs and pads (SSBC), or the master/booster combo (MBM)?

Cheers,

Al.

Is suspect it its a booster/master issue, every 2nd person seems to have an issue getting them to stop, but like I say I've never tried to fix one.