If you have the Chrysler master that most use , it’s a 70% to the front 30% to the rear from the factory.

they want you to swap the port’s because most drag cars run skinny front tires and at the top end the would lock up and pop the tires.

usually they don’t use a proportioning Valve when doing this.

I like having an adjustable Proportioning Valve to tailor my application personally. They will tell you if install one to keep it wide open.

I hope this is what information you needed?

I always wanted a 67,68 Mustang Bad Ass car ! Care to share a little bit about it?

I set my master line lock and adjustable Proportioning Valve up so I could just reach it at will. See picture.

 

Sorry I forgot to mention I use this wilwood master cylinder 260-15521-BK

The Mustang has a full aluminum engine 438 ci with close to 800 hp on normal fuel. PG completely build to my specs only the finest stuff. Suspension is nothing wild but nice with strange shocks, 9" from currie, mono leafs etc. just an old school drag racer.

 

Did you add roller spring perches? I have two 67 fastbacks and made my own…. Wow do they make a difference!

 

Don't guess.

Brake Pressure Test Gauge (strangeengineering.net)

What Brake Pressure Do I Need ? - Strange Engineering

 

I know that there is enough brake pressure. But my question is why should I change the brake lines when I can lock my rear brakes with the usual setup, I´m just scared that I will have more power on the rear brakes what is not needed.

 

I know that there is enough brake pressure.
But my question is why should I change the brake lines when I can lock my rear brakes with the usual setup,
I´m just scared that I will have more power on the rear brakes what is not needed.

I'm no expert, but I would rather have it the way you have it now.
Sounds like the perfect balance, I would much rather have the rears lock up well before the fronts.

Good luck.


.

 

You could always install a proportioning valve and customize the braking to whatever you fancy! 👍

 

I was always under the impression that the rear port of the master had the ability to move a larger volume of fluid. So that port would be used for whichever axle has more combined brake piston area, and not a hard rule of “the rear port always does the front brakes,” or “the rear port always does the rear brakes.”

 

IMO it's better to lock up the front brakes. Locking up the rear brakes will make the car swap ends, kinda like a "dukes of hazard" 180* spin when you grab the emergency brake.

 

I´m not sure if its so good to lock skinny drag tires on the front as they will stand really quick and then blow up in smoke but no braking force will be applied to ground. And when I swap the ports my fear is that there will be more braking force on the rears than now.

For the roller spring perches where is the difference? I always think about it but never did it.

 

They transfer weight sooo much better. An investment you will notice immediately.

As for braking,just put an adjustable proportioning valve on it.

 

The problem with balancing brakes is what is good at 40-60mph may bite your ass at higher speeds depending on the aerodynamics of the car. My stock body Fox Mustang gets light in the ass at higher speeds. Once I went thru the traps at high 150s and started my normal aggressive braking (not a panic stop). I felt the rear get loose and fortunately reacted correctly by letting up on the brakes. I think it may have been dew settling on the track as was late at night when the dew starts to form on the car tops.

And no, I would NEVER set up a car to lock up the rears first. Like someone mentioned, it's highly unstable and can easily send the car in a spin.

 

ok what I don't understand as a real good racer driver, for me when the ass is planted down to the ground and my rear start to lock up its better than a locking front with skinny tires that will raise the ass of the car and make it light there. I maybe need to mention that my car is good planted to the ground on all 4 wheels even with the locked rear. Maybe its sketchy to make a full stop on our shortest track. But it doesn't feel totally weird or wrong.

My only question was when I swap the ports that I will have more power on the rears than now and so they would lock up faster what is not good, right.?

Ok I wil check fro some roller spring perches maybe someone has them at the moment.

 

For drag racing, the port that is closest to the brake push rod goes to the rear brakes. The initial pressure should go to the widest tire first. If you run the initial pressure to the front you risk front tire lock up..... which is easy to do, due to the narrow front tire.

 

Exactly what I thought. thank you, but a lot of people do this swap and switch the ports.

 

Use more aggressive pads where you want more brake bias.
Proportioning valves often cause brake drag as they rarely fully release

 

You have a straight bore MC, the only difference between ports would be possibly a little volume. It can't have more pressure as both ports have the same size pistons pressed by the same pedal.

 

Amazing how many people do not understand this

 

Thank you all, I think this thread has so many informations that no one need to ask this question again. The volume is exactly the same in my master cylinder. So I stay like it is and just buy some more aggressive pads for the front. This idea was one of the best, thanks Matty and yes I also don't want a piece more in the puzzle like a proportioning valve so the idea with the pads sounds really good and maybe that's how I come to the perfect solution that my front brakes bite a little bit more.

 

.

I just checked my no box car.
It's a BBC 2nd gen that uses a stock Vette manual master with Wilwood's all four.
8.90 car with 10" tires.

The aftermarket proportional valve is on the rears full CW.
I have had zero issues using the brakes at the stripe, and I admit I have pressed a touch harder than I probably should a few times.

I also have the back port feeding the front brakes.

This thing has been a racecar for over 25 years and I have no clue what I changed or didn't change back then.
I'm assuming I matched the ports, and matched where the stock proportioning valve was??

 

Hello I´m working a lot on my 68 Mustang and I talked to Wilwood and they told me that I need to change my setup and put the front brakes on the rear port of my master cylinder and the rear brakes to the front port of my master cylinder.

But I know when I brake aggressive and hard that my rear tires can lock up also at higher speeds but my front don't. And that is with the usual setup front port to front brake and rear port to rear brake. All around Draglite Wildwood 4 pistons.

I use this master cylinder Wilwood 260-15521-BK

Does someone has a good idea on that and is it really necessary to do this, I´m scared that there will be much more braking power then and my rear will lock up more than now and maybe faster.

Thanks for the help.

And yes the car is very light with full aluminum engine etc.

View attachment 456421

lol, buy a M1931 master,I have installed over 75 of them since 1983, 4700 pound 10sec cars to 18oolb 7 sec cars rs, 4w drums 4w disc brakes what ever.
about every combo you can think of works great, with P Valves,and with out, on 64 thru 68 without
with stock brakes.aerospace,strange etc etc
also used it on power brake cars, works perfect on man/brake cars

big brakes,or small

 

Do you mean the classic mustang master cylinder or the strange look a like? Do you maybe have a picture?

 

I will try to rem to take a pic today, It looks like an OEM,its alum,( LITE WEIGHT )so it wont get rusty,and the lines come out toward the driver's side fender, looks like a factory with a spring overtop clip. Its from 1983/ 84 manual brake rangers. I have sold a few to guys on here also,you might be able to do a search.


Oh, I have switched lines on these front to back, and back to front,lol. MAKES NO DIFF, EITHER WAY, WORKS PERFECTLY. EVERYBODY loves them

 

 

Truth of the matter at hand is.....there is NO mystery at all. There is the right way, and the wrong way.....

 

with your part number I can't find them

 

https://www.autozone.com/brakes-and-traction-control/master-cylinder-brake-system/p/duralast-new-brake-master-cylinder-nm1931/248442_0_0

 

If you didn’t get the application in his reply it’s a a Raybestos MC39401 at RockAuto for $92. It has a 15/16” bore.

 

I cannot seem to get a picture to post PM me your cell number I’ll gladly send you pictures

Also, I have switched the front brake lines to the rear to master and the rear to the front and back and forth. I’ve done that with this master it’s made no difference. The brakes have always worked great.