New Brake Lines-- Spriso Motorsports Style, a Tutorial

[spriso]

Since I have had several requests, I will write a tutorial on how we at Spriso Motorsports rebuild brake (and fuel) lines on our SR conversions in Datsun roadsters. I am doing an SR conversion for a customer in Canada right now, and will be building a full set of brake lines over the next few weekends, so I can go into full detail about what we do. This thread will be photo intensive, and will hopefully answer your questions.

At every show we go to, our brake line conversions are one of the first thing that people ask about... this is not rocket science, nor is it terribly difficult to do, but it does require practice, some new tools, and attention to detail.

First, let us take a look at a typical un-restored 67.5 and later engine compartment:



A thing of beauty, isn't it? Hmmm. I did not think so either.

What we do is something like this:



Since I am building this thread from photos from my library, bear with me in the fact that I am missing a cross-over brake line from the t-fitting to the passenger side of the car-- but trust me, it was hidden too!

The best part of doing the work to rebuild your brake lines is the fact of what people DON'T notice anymore-- and that is the stock mess! With the engine installed, everything kind of disappears-- they are no longer a focal point in the engine compartment, which is EXACTLY what we want!

No more distracting brake lines:



So, stay tuned, I will go through the tools, the routing, fasteners, etc. Everything that we know about brake lines and how we do them on our conversions!

Michael Spreadbury
spriso motorsports

[Dcyco1]

Dam that was fast! Can't wait to see more.

[Alvin]

subscribed
thanks for the how to

[spriso]

Ok, so let's talk about the stock roadster brake line plumbing. The stock (67.5-70) roadster brake master cylinder is a 3/4" SAE fitting master cylinder. This was the first dual reservoir master cylinder that Datsun put on North American cars/trucks. Because the roadster was designed for the Japanese market, it was originally configured for right hand drive. When the car was converted to left hand drive for export markets, the longer dual reservoir master cylinder hit the air cleaner assembly. Datsun's solution was to build a 'pocket' for the master cylinder to sit in, moving the master cylinder away from the air cleaner. A good solution for the problem...



From the master cylinder, the brake lines run across the firewall to the pressure switch/junction box located on the passenger side of the firewall. PASSENGER SIDE-- remember that. So, lets follow those brake lines from the master cylinder to the pressure switch/junction box. Now things get messy.

Across the firewall:



To the pressure switch/junction box:



Now, the driver's front brake needs a hard line run to it, so back across the firewall we go with ANOTHER brake line.... this right hand drive, to left hand drive conversion that Datsun engineered is not looking so impressive now... Back and forth, back and forth. We have 20+ feet of brake line in the engine compartment because Datsun did not want to move their pressure switch, and rear brake hard line!

It was a mess when it was new, and then add 40+ years of ham-fisted owners messing with the brake lines, and you end up with a disaster. Even cars that have been well maintained and freshened up still have brake line challenges:



We can do better. Much better...



By the way, the last two shots are the same car-- before and after!

Michael

[spl310]

You do exceptionally nice detail work. Just curious, why is it that you delete the pressure switch?

[notoptoy]

Once again, works of art!
Thanks!

[23yrRebuild]

I know the restos are two different cars, but in the very last picture, it looks like the lines from the master cylinders are penetrating the inner fender skirt rather than heading down and over to the passenger side as shown in the second picture. I'm curious about that.

I can't wait to what see this line re-routing would look like in a stock engine bay.

[spriso]

Sid wrote:

You do exceptionally nice detail work. Just curious, why is it that you delete the pressure switch?

There are two reasons why we get rid of the stock pressure switch. The first is that we can eliminate 2 of the brake lines by going with a simple 3-way T-fitting, and the second is that instead of using the pressure switch to activate the brake lights (on early cars), we use a conventional brake line switch at the pedal. This cleans up the engine compartment, gets rid of redundant components that are not necessary.

23yrRebuild wrote:

I know the restos are two different cars, but in the very last picture, it looks like the lines from the master cylinders are penetrating the inner fender skirt rather than heading down and over to the passenger side as shown in the second picture. I'm curious about that.

You are correct. Different builds, different techniques. On turbo conversions, we want to get the brake lines out of the engine compartment as soon as possible, so we route them out of the compartment, down the inner fender, to a T-fitting. I can show this more in detail later.

On normally aspirated cars, where exhaust heat is not an issue, we cross over for the front brake and clutch line just as you would on a normal setup. We re-route the rear brake line to run down the driver's side of the car (to eliminate another cross over brake line!) Again, I will show this in more detail as this post gets developed.

Michael

[spl310]

There are two reasons why we get rid of the stock pressure switch. The first is that we can eliminate 2 of the brake lines by going with a simple 3-way T-fitting, and the second is that instead of using the pressure switch to activate the brake lights (on early cars), we use a conventional brake line switch at the pedal. This cleans up the engine compartment, gets rid of redundant components that are not necessary.


Michael

I can understand the desire to reduce lines, but the pressure switch is a safety device to let you know of an imbalance in the brake system (IE: losing a caliper or wheel cylinder). I would think that would be a feature you would want to keep. On the pressure switch for the brake lights, I can understand wanting to get rid of it - I have had two fail...

[ppeters914]

There are two reasons why we get rid of the stock pressure switch. The first is that we can eliminate 2 of the brake lines by going with a simple 3-way T-fitting, and the second is that instead of using the pressure switch to activate the brake lights (on early cars), we use a conventional brake line switch at the pedal. This cleans up the engine compartment, gets rid of redundant components that are not necessary.


Michael

I can understand the desire to reduce lines, but the pressure switch is a safety device to let you know of an imbalance in the brake system (IE: losing a caliper or wheel cylinder). I would think that would be a feature you would want to keep. On the pressure switch for the brake lights, I can understand wanting to get rid of it - I have had two fail...

I thought its only purpose was to trigger the rear brake lights.

[spl310]

On the pre 68 cars, the switch is the brake light switch. On the 68 - 70 cars, that block senses a differential in brake pressure between the circuits, and trips a switch - that switch turns on the B (brake) light on the dash. (yes, the same light that the S/Brake switch turns on) to let you know of the failure. The 67.5 cars and earlier have no warning light. The pre 67.5 cars have a different warning indicator - the sound of your pedal solidly hitting the floor...

[spriso]

Sid brings up an interesting point about the pressure switch, however it has been our experience that it is not needed. The dual reservoir master cylinders are two different circuits one for the rear of the car, one for the front. We are adding the T-fitting for the front circuit, and the rear is plumbed directly to the rear brakes. If we were running a single reservoir master cylinder, then yes, a break in the line could cause the whole system to fail. This is not the case on the dual reservoir systems however. You can have a cut or disabled front or rear brake line and the brakes will still work, albeit with limited capacity. As a back up, the rear mechanical drum brakes will also still function independently of the hydraulic system.

I like to think that the pressure switch is probably one of the most misunderstood parts of the system. Many people assume that the pressure switch/junction box is a "brake bias" valve, but that is not the case at all. When we rebuild the brake lines, we do add a mechanical brake bias valve to the rear brake circuit, but that is an aftermarket Wilwood unit.... I will show that later in this thread.

Yes, you loose the function of the "B" light when you re-plumb the system our way, but I can be pretty confident that few roadster owners know what the "B" light function was, nor are they still functioning. We turn the "B" light into a charge light (ie. "Battery") when we rewire the cars for an internally regulated alternator. If someone insisted that they retain the pressure switch, it could be re-routed to the inner fender on the driver's side of the car and the wiring updated to keep it intact. There is no law saying that it needs to stay where it was originally.

We prefer the simpler solution however without the clutter and unnecessary plumbing. We have rebuilt the brake systems on a lot of roadsters. We always use new components, critically think about the routing and placement of hard and flex lines, and properly secure the systems. Brake systems are something to take very seriously-- your life and others depend on it!

Michael

[S Allen]

As always Michael truly amazing attention to detail.

Steve

[dbrick]

Hi Michael, great work as usual. I understand Sid's question and your answer. The brake warning light is one of those odd safety things. For someone with no knowledge of cars at all, a big red light on the dash when the brake pedal drops halfway and the car isn't stopping as well as normal is a good thing. Anyone who really pays attention to how their car feels will notice the failure immediately and take steps to address it. The government has to makes safety rules geared toward the most ignorant (not stupid) drivers. Ironic thing is after 40 years, I doubt most of the valves work anyway.

BTW, saw this, a new part from Wilwood 260-11179 Combination Proportioning Valve. Looks like a nice piece. Not as clean as the "T", but has the switch, proportioning valve and a split for the fronts.
http://www.jegs.com/i/Wilwood/950/260-11179/10002/-1

[23yrRebuild]

Can a proportioning valve somehow be used to make the rear drums brake more? I'm under the impression these valves reduce pressure, so in order to increase rear braking, it would need to be in the front brake circuit. Any comment?