Help and Comments Please: Big Brake Upgrade on AC Cobra MK1

[maginter]

OK, I have been going through digging into those upgrades I want to do and as I uncover one thing I am researching, I uncover another obstacle. So, I am back to ask for more help and comments.

The MK1 I have is an old build and was built with a 1993 donor. I have discs in the front and drums in the back and has manual brakes. As configured, I am not a fan, but in all fairness, I don't think that the setup is correct as it was recently done by the previous owner converting to 5 lug hubs. I would like to go to the bigger brake upgrade with 4 wheel disc. It would be the 2003 Cobra caliper/disc configuration. I have the mechanicals sorted out, but do have a question on the master cylinder. I know I will need a bigger bore, which is no issue, however I am seeing applications that all seem to be upgrading to a power brakes form manual with a brake booster with the new master cylinder.

So, I have a couple of questions:

1) Are their people out there that have done this upgrade to an MK1 Roadster?

2) People doing this upgrade on an MK1, are you using a brake booster and is it required?

3) How are you able to fit a booster into that space if used?

4) If running without booster, does it still have good performance?

Thanks is advance!

Mark

[CraigS]

The vac booster requires cutting the 3/4x3/4" tube that runs out from firewall to LF suspension. There is a kit that has a filler piece but I didn't like that idea. What I would do if I were you is get the largest rear disc kit I can find and install it. Then run Hawk HP+ pads in the rear w/ HPS5.0 in the front. The Mustang based brakes were balanced for a front heavy car but the FFR is rear heavy so those brakes lack rear grip. Going as large as you can in the rear and also staggering pad compounds will help a ton. HPS5.0 are very grippy and HP+ are super grippy. The HP+ will dust some so I use this to make the wheels stay clean longer.
https://www.armorall.com/product/outlast-brake-dust-repellent/

[maginter]

The vac booster requires cutting the 3/4x3/4" tube that runs out from firewall to LF suspension. There is a kit that has a filler piece but I didn't like that idea. What I would do if I were you is get the largest rear disc kit I can find and install it. Then run Hawk HP+ pads in the rear w/ HPS5.0 in the front. The Mustang based brakes were balanced for a front heavy car but the FFR is rear heavy so those brakes lack rear grip. Going as large as you can in the rear and also staggering pad compounds will help a ton. HPS5.0 are very grippy and HP+ are super grippy. The HP+ will dust some so I use this to make the wheels stay clean longer.
https://www.armorall.com/product/outlast-brake-dust-repellent/

Thanks for the feedback! So, just change out the rears and go from there.... OK, but I do have some additional questions with this configuration.

1) My assumption is that I will need a larger bore MC, replacing the 1993 MC, correct?

2) The previous owner did a 5 lug upgrade, but the front was still the 1993 spindle. In this setup that rotor looks like it is pushed out to far.
- Should I still do the 94-95 spindle swap still using the caliper I have on the car? (Pic attached)

3) Do I leave the Pedal Ratio the same for the brake pedal? (93 Pedal Box)

[rich grsc]

NO, you do not need a larger bore MC. Where did you get that idea?
Yes you leave the pedal the same as long as you keep manual brakes

[David Williamson]

I did the 5 bolt conversion when I built my Mkll using a 93 GT donor, the front rotors are from a Lincon Mk7. The Lincon front brakes are the same as the Mustang ones except 5 bolt so it was an easy change. What you have looks correct.
David W

[maginter]

NO, you do not need a larger bore MC. Where did you get that idea?
Yes you leave the pedal the same as long as you keep manual brakes

I am still pulling information from everyone's builds. The consensus for the move to big brakes 4 wheel disc is to go with a larger MC, however. if I would have thought about it, I am not increasing the front, so I don't need the extra volume. Since I have purchased the car, the brakes take a lot of effort to get the car stopped. I am just asking all the questions now so I know what to dig into in the next layer.... Thanks for your feedback!

[maginter]

I did the 5 bolt conversion when I built my Mkll using a 93 GT donor, the front rotors are from a Lincon Mk7. The Lincon front brakes are the same as the Mustang ones except 5 bolt so it was an easy change. What you have looks correct.
David W

OK, thanks! This helps!

[Jeff Kleiner]

First and most important question before we go any farther—-was the brake pedal modification done when it was converted from power to manual brakes?

Jeff

[maginter]

First and most important question before we go any farther—-was the brake pedal modification done when it was converted from power to manual brakes?

Jeff

I cannot answer that question and need to look. What am I looking for? Isn't this the linkage movement to a different hole.... or maybe not. I read something about that some time ago, but made the assumption it was correct. I know..... don't make assumptions with these builds....

What do I need to look at in the pedal box?

[Jeff Kleiner]

The mod is to change the pedal ratio and can be accomplished multiple ways. One is to cut and reweld the pedal between the pedal box pivot and pushrod stub. Another is to move the pushrod actuation point as described here:

http://www.norcal-cobras.com/projects/brakes/brake_pedal.htm

Mike Everson offers a pedal exchange service which relocates the upper pivot bushing:

http://www.replicaparts.com/brake%20pedal%20mod.htm

However you go about it the goal is to have the pedal box pivot point and the pushrod actuation point about 2 1/4" apart on the arm. You'll have to get in there and do some checking and measuring to see what you've got. If the pedal hasn't been reconfigured to correct the ratio you'll just be chasing your tail with further changes.

Jeff

[maginter]

The mod is to change the pedal ratio and can be accomplished multiple ways. One is to cut and reweld the pedal between the pedal box pivot and pushrod stub. Another is to move the pushrod actuation point as described here:

http://www.norcal-cobras.com/projects/brakes/brake_pedal.htm

Mike Everson offers a pedal exchange service which relocates the upper pivot bushing:

http://www.replicaparts.com/brake%20pedal%20mod.htm

However you go about it the goal is to have the pedal box pivot point and the pushrod actuation point about 2 1/4" apart on the arm. You'll have to get in there and do some checking and measuring to see what you've got. If the pedal hasn't been reconfigured to correct the ratio you'll just be chasing your tail with further changes.

Jeff

Thanks Jeff, this is really helpful and it looks like I have some more digging this weekend and report back

[David Williamson]

Going back in the memory bank from 20 years ago when I built my Mkll. I have the full 93 GT donor brakes on my car same as yours except I kept the power. One item that lots of us did back then was to remove the rear proportioning valve so the back brakes had more hydrulic pressure. Ford sold a plug that let you take the proportioning valve out of the distribution block. I have toyed with upgrading the back brakes to discs over the years but have not done it because what I have works fine, it would be more just for cosmetics and hard to justify the $$. So the old Mkll is the only car of 4 we have with back drums and no IRS
David W

[CraigS]

You don't really want to just substitute 94/95 spindles. They are maybe 1.5" shorter than Fox spindles and require more than just swapping them in. I would concentrate on the brakes for now and leave the front suspension for later. I did the FFR spindle conversion on my mkII so can fill you in on what that entails later on.

[maginter]

Thanks Jeff, this is really helpful and it looks like I have some more digging this weekend and report back

OK< I did some digging around above and below the pedal box and have some information to continue my work.

I did measure the distance from the center of the pivot point and the pushrod actuation point. It was as exact as I can get, but it is currently at 3 3/4 inches. So, the pedal has not been modified. I have to say that I am not real impressed with the builders pushrod, but that is another story.

So, I will need to send the pedal off for a swap. This does prompt a few question:
1) Moving the distance closer will result in the need for new holes for the pivot point to keep the pushrod inline with the master cylinder, correct?
2) Does this require the removal of the pedal box, or are there holes there already? (Guessing it needs to me removed)
3) Assuming the pedal box needs to come out, are there other mods that need to be done for accelerator or clutch pedals?

Thanks again for all your help

[CraigS]

Usually there is another pair of holes already in the sides of the pedal box. The pedal arm gets shortened between the pivot and the pushrod. This way the pivot is lower and matches the placement of the other set of holes so the pushrod to the MC stays in the same place relative to the MC. The red box indicates where it will be cut.
204451
When I did mine I had to cut the aluminum on the outer side of the footwell to get the pivot bolt out. I cut a 3 sided square and used the 4th side as a hinge to bend the aluminum out of the way. When done, I bent it back and sealed it w/ silicone sealer.