Questions on 83 brake swap

Topic: Questions on 83 brake swap (Read 2826 times) previous topic - next topic

Questions on 83 brake swap

May 02, 2016, 10:37:15 AM

First off I searched all over this forum but surprisingly I didnt find my answers.

On my 83 TC Im planning to upgrade the brakes but have a couple questions to those who have done this before me.

So far I have a 88 TC 8.8 that will be going in with all new parts.
I also have 87 GT front 11" setup.

I have an adjustable proportioning valve and plan to run new lines to get rid of the stock valve.

Now my question is about the booster and the master. On paper it looks like Im building a 93 Cobra brake system so is it safe to assume thats the master I want to use? If so is the stock 83 TC booster fine to use? I see the 93 Cobras got a different booster but I dont know why. If a booster swap is needed what is the best option?

Questions on 83 brake swap

Reply #1 – May 02, 2016, 08:19:25 PM

I have an '83 Heritage with the factory 5.0, but am on a parallel path.

I have an 87-88 TC rear end going under the car, and I am at this very moment replacing the original steering knuckles and front brakes with 11" 87-88 TC rotors and 73mm Lincoln calipers.

I started a while back by first replacing my rotten master cylinder and booster, and for that I used a '93 Cobra booster, and an '85 Crown Vic master cylinder that has a 1-1/8" bore. The plumbing was pretty simple, as it was two connections at the master cylinder for both the original and the new master cylinders. The fittings required different threads, but the original nuts were rounded badly and the lines were too short, so I needed to make new ones between the master and prop valve, anyway.

You can use the newer master cylinder, but you will also need a line adapter, as the newer master cylinder has more than 2 line ports.

My somewhat heavier 80's master was brand new, and cost $25, and I had it delivered to my FLAPS same day. The '93 cobra master (I believe it was remanufactured instead of new) was something like $130 and four business days away. I accepted the older style cast iron unit which was more affordable and more easily available, but, absolute weight savings isn't a "money is no object" factor for me, or I may have decided in favour of the later aluminum/plastic Cobra master.

Questions on 83 brake swap

Reply #2 – May 02, 2016, 08:41:02 PM

Whoops. I forget to go in to detail about the booster.

I left out that briefly, I had used a remanufactured '83 booster with the larger Lincoln master cylinder, because it was a good deal less expensive, and much more easily obtained. With it, the brakes were extremely under boosted, and not much improved over manual brakes. It took more effort than my tired knees wanted, and upon testing it the same day it was installed, I returned to the store and ordered the Cobra booster. I continued using the reman '83 booster for the week it took to get the Cobra booster in. (Luckily, the manager at my FLAPS loves me, and puts up with the crazy shopping lists my projects all seem to require.)

As far as differences between the original style booster and the Cobra booster go, the Cobra booster is smaller in diameter, but deeper. Installing it in my '83 required slightly hammering in a bit of the shock tower about 3/16", and slightly slotting the mounting holes in the firewall. I also chose to paint the remanufactured brake booster with black semi-gloss chassis paint, because the remanufactured brake booster came straight out of the box in bare steel with oil on it. I was in a rush and out of 2k epoxy, so I used Por-15 brand chassis black once I had the fitment details worked out.

What other differences are there? I honestly have no idea, but it sure does make for an easy to use brake pedal once you throw that big-bore master cylinder under the hood.

Which proportioning valve have you settled on? I went with a Wilwood unit that several others here have used.

Questions on 83 brake swap

Reply #3 – May 02, 2016, 08:59:50 PM

Ok so I guess Im looking for that booster now too.

I have Summits copy of your Wilwood

Questions on 83 brake swap

Reply #4 – May 03, 2016, 05:30:37 AM

The Cardone remanufactured '93 Mustang Cobra booster is part no. 54-73155. I had a heck of a time finding an online source that actually had them in stock, and eventually ordered mine locally through CarQuest. CarQuest has now merged with Advance Auto, and the booster is available for about $100, not including the core charge. As an added bonus, it's eligible for a 20% off savings by purchasing online, but you can still pick up online purchases in store.

Rock Auto seems to have the best price from a quick check I just did, and it seems to actually be in stock currently. The downside for me would be shipping back the core. I always disliked needing to ship a core back for a refund.

As for the Wilwood/Summit prop valve, I very nearly picked up the Summit branded version myself, but at the time I found one on Amazon for $10 less that included free Prime shipping.

Questions on 83 brake swap

Reply #5 – May 03, 2016, 10:23:02 AM

Over on FEP it was suggested to use a 94-95 booster as well since they are more readily available

Questions on 83 brake swap

Reply #6 – May 03, 2016, 11:31:29 AM

I may be a day late and a dollar short but using the 1-1/8" bore MC is not what I would call optimum with the stock Fox 5.0 Mustang or 87-88 TC front brakes and the TC rear brakes. You really need a 1" bore MC which is what came on the 93 Cobra. Our cars have SAE threads on the MC so you can substitute an 85 Lincoln Town Car MC which is the old school style MC but has a 1" bore, SAE threads, two ports, and I have seen them come in aluminum but mostly you get a cast iron body. The reason a Cobra booster works so well with the 1-1/8" bore MC is that the pedal effort went up due to the larger bore of the MC and the Cobra booster is a higher multiplier than the stock T-Bird booster. The 1-1/8" MC will push more fluid but at a lower pressure due to the larger piston diameter. You can run the stock style Thunderbird booster and a MC with a 1" bore and not have any issues. To illustrate here is some data on the braking systems.

The Fox 5.0 Mustangs, the 93 Cobra, and TC front brakes all have 11" rotors and a brake caliper with a 2.358" (60mm) piston. The SVO Mustang and the Lincoln Mark VII also have an 11" rotor but have a caliper with a 2.876" (73mm) piston. All of these vehicles share the same spindle assembly and rotors so that is why the calipers are interchangeable. The TC and 93 Cobra have rear calipers with 1.786" pistons where the SVO and Lincoln Mark VII have 2.121" pistons. Now you can see why they ran the 1-1/8" bore MC on the Mark VII and SVO Mustangs due to the larger diameter of the pistons on the front and rear calipers taking more fluid to fill up the caliper body and displace the piston.

Running the larger diameter MC with the smaller bore calipers is not needed volume wise and will increase pedal effort due to the larger diameter piston reducing the pressure exerted on the braking system. Remember, the smaller area the force acts upon the higher the pressure being that pressure is the force displaced on area or pounds per square inch (psi).

The Cobra and SN95 boosters are a dual diaphragm unit so they can be smaller in overall diameter but have a larger area that the vacuum acts upon and can deliver more pressure with the same stroke brake pedal assembly than the stock single diaphragm booster that comes on all the Fox Mustangs, T-Birds, and Cougars minus the 93 Cobra.

The other issue you need to watch out for is brake bias which when mixing and matching brake parts like using the larger bore SVO/Mark VII calipers up front and the smaller bore Cobra/TC calipers out back with a large bore MC. The car will simply not stop as well as it would with the 1" bore MC and the smaller brake calipers up front or the large bore MC with large bore calipers on all four corners but that would then require utilizing the Mark VII rear end.

Do not forget that if you do all of this you will need to gut the proportioning side of the combination valve and install a manual proportioning valve for the rear brakes to dial the rear brakes in.

Questions on 83 brake swap

Reply #7 – May 03, 2016, 11:48:33 AM

So let's say you decided to go with the 1" MC, 60mm front calipers, and the 45mm rear calipers and either the stock booster or the Cobra booster. You put the system together and it just does not quite have enough stopping power. Now it is time to look at brake pad compounds as the they deal at the local parts stores is barely OEM. I would suggest EBC or Hawk brake pads as they both make some that are low dust and have some serious stopping power.

By the time you do all of this you could have swapped out to SN95 brakes and moved to dual piston 44mm front calipers (slight mod to 94-98 spindle to use these 99+ calipers) and made the move to five lug. The usual show stopper here is five lug rims and tires but I will tell you that the difference between the hopped up Fox system and the SN95 system (same for GT and V6 cars) is light night and day.

Questions on 83 brake swap

Reply #8 – May 03, 2016, 12:06:07 PM

1985 Lincoln what? 2wd? a/c? rwd? flexfuel?

EBC pads were always part of the plan as well.

SN95 brakes and 5 lug swap was never in the plans. I already have new 93 Cobra wheels and new tires on the car and I have two 88 TC 8.8 here to pick from. Im just looking to optimize my swap around the parts I already have to work with. I need this car done fast and for as little out of pocket as possible since Im still building my drag truck at the same time as this car.

Questions on 83 brake swap

Reply #9 – May 03, 2016, 12:14:06 PM

85 Lincoln Town Car. Good choice on the pads and completely understand about going five lug. I would stay with the 60mm front calipers and 45mm rear calipers with a 1" MC and you should be fine. Booster wise the difference between the 93 Cobra unit and the SN95 units is the bolting pattern on the fire wall. You have to slot the out of the fire wall to get the SN95 units to work but the Cobra require little to none if you have done a few.

Questions on 83 brake swap

Reply #10 – May 03, 2016, 12:19:31 PM

Thanks for the help, that sounds like the recipe I will follow. Maybe just a new stock booster for the 83 TC to start with and see how it feels.

Questions on 83 brake swap

Reply #11 – May 03, 2016, 04:21:54 PM

Aerocoupe knows his stuff. I have read a lot of his posts in my research.

What I put together is based on using 73mm front calipers, with the expectation that if I can figure out how to so, upgrading to larger than the '87-'88 TC rear calipers, too. (I have not pulled it off yet.)

It lookes like Aerocoupe believes that 73mm pistons are not worthwhile, and that without them, there is no need for more than a 1" bore, and I agree with him that the 1-1/8" bore is not needed if you aren't going to move up to the 73mm pistons, but I thought they were worth trying for the slightly better pad support the larger piston offers. I do think that the Cobra booster is the way to go either way, as it really makes the brake pedal action feel much more modern.

That all said, if money isn't a problem, then going five lug is the key to accessing really good brake performance. I just don't have that kind of money to throw at mine, and even if I did, I have a diesel Eurotrash toy that I would spend it on first.