Building a classic truck is a rewarding experience, particularly when you get to drive the end result, but there are also some sobering realities involved in assembling an automobile from the ground up. First off, despite what you may see on TV, it takes more than a couple of weeks for the average person to do it. Secondly, you and your loved ones will be riding in it, so the importance of building a safe truck above all else can't be overstated. One of the tasks involved in truck construction that is both time-consuming and critical to functionality is plumbing. Last month we looked at the variety of fittings commonly used, so this time around we're going to give you a few tips and tricks on how to hook them together.
Brake Lines
First let's deal with a common misconception-the relationship between brake line size and hydraulic pressure. Simply put, there is no relationship. The master cylinder establishes the pressure in a brake system; all the lines do is deliver the pressurized fluid.
Brake lines are most often 3/16- or 1/4-inch-diameter and, while there will be no pressure difference between the two, there be a difference in the amount of fluid delivered. The bigger tubing will carry more volume, so 1/4-inch line may be preferable in some instances, four-wheel disc brakes as an example.
Regardless of the size, when it comes to selecting the type of rigid brake lines to use, there are only two choices: steel or stainless steel. Copper or aluminum should never be used. And Gary Clausen of Pure Choice Motorsports points out that excessively long lengths of flex line, including the braided variety, should not be used, as a spongy pedal will result.
One of the most common mistakes made when plumbing a chassis has to do with routing; brake and fuel lines should be a minimum of 3 inches away from any significant heat sources, most notably the exhaust system. And while it's a little off the subject of plumbing, we have to mention the problems associated with positioning the exhaust pipe too close to an underfloor master cylinder. It is very common for these components to be quite close, but be aware that a master cylinder, and the fluid it contains, will readily absorb heat. We've seen instances where the proximity of the master cylinder to the exhaust was such that the fluid would get hot enough to expand and make the brakes drag, or in the worst-case scenario, not release after being applied. If you opt for an underfloor master cylinder and the exhaust pipe is anywhere in the area, consider fabricating some sort of heat shield.
Another important consideration when plumbing a chassis is securing the lines. Clausen recommends using clamps every 18 to 24 inches for adequate support. Putting bends in lines cause them to be more rigid, but too many clamps isn't the problem that too few are. But while the goal would normally be to hold a line secure, there are cases where movement is necessary. Take for example firewall-mounted master cylinders. There is usually some movement between the body and frame, so that needs to be taken into consideration when installing the lines. One method is a short flex line between the body and frame. Another is what's called a vibration loop. Clausen recommends putting several coils in the line to provide the needed flexibility.
Flex Lines
When measuring for flex lines it is critical that suspension travel and wheel movement are taken into consideration. The front wheels must be able to turn lock-to-lock and both axles must be able to go through full suspension compression and rebound without putting stress on the hoses. More than one rodder has checked compression travel then jacked their car up only to find out the hoses weren't long enough when the wheels dropped.
Although flex lines are necessary, excessive use in the brake system will result in a spongy brake pedal.
There are loads of handy tools...
There are loads of handy tools to make plumbing a chassis easier. This handy little device from Made For You Products makes it easy to determine line size.
In our minds there have been...
In our minds there have been two great inventions-crackers with peanut butter already on them and this flaring tool from Pure Choice Motorsports.
There are two kinds of rodders...
There are two kinds of rodders in the world-those who have flared lines without putting the nut in place first and those who are going to. Just remember, this is the first step.
We opted to use steel brake...
We opted to use steel brake lines for our Model A. And while various lengths of flared tubing is available at most parts houses, we elected to buy tubing in bulk, cut it to length, and flare the ends. The first step is to cut the end of the tubing square, deburr it, and then clamp it into the tool.
Steel lines require a 45-degree,...
Steel lines require a 45-degree, double-inverted flare. That means the tubing is folded back on itself. A special die is used in the flaring tool to begin the process; this is what the first step of the operation looks like.
With the first part of the...
With the first part of the flare formed, the dies are changed in the tool for the second operation. This step will establish the 45-degree seat.
In addition to g-flares, this...
In addition to g-flares, this tool will also form the proper ends for GM automatic transmission cooler lines. By trimming the ends, this same treatment can be used for extra security with hose and clamps.
When bending tubing, we make...
When bending tubing, we make reference marks at the middle of one bend to the middle of the next. It takes practice, but eventually you'll get all the bends in the correct place the proper distance apart.
Clausen showed us a neat trick;...
Clausen showed us a neat trick; here he uses a file to make the surfaces around the outlet ports of this master flat so banjo fittings can be installed.
Fuel Lines
Many of the considerations concerning the placement of brake lines apply to the fuel system as well. And while steel and stainless steel are the recommended materials for hard lines, aluminum tubing is sometimes used.
Aluminum tubing is light-that's why it's often found on race cars-but it chafes easily and needs more support than steel or stainless steel. For most carbureted applications, 3/8-inch line is adequate, although high-horsepower engines may require 1/2-inch for enough fuel volume.
When plumbing the fuel system, keep in mind that today's gasoline additives (including alcohol) will cause conventional hose to deteriorate. Plan on replacing any rubber hose in the system every two years, or bite the bullet at the outset and buy the best braided hose with an inner liner you can find.
Ready, Set, Plumb
Before you begin to plumb a truck chassis, here are some suggestions from the experts at Pure Choice Motorsports:
• Identify the type of plumbing you want to use (stainless steel or steel).
• Match the fittings to the type of flare used: AN fittings use 37-degree flares, SAE use 45-degree, double-inverted flares.
• Use quality tools for installation to prevent rounding off fittings.
• Do not over-tighten fittings. AN fittings should be snugged finger-tight then tightened approximately a quarter-turn. While 45-degree fittings require slightly more torque to seal, over-tightening should still be avoided.
• Use anti-seize on all aluminum-to-aluminum or stainless-to-stainless fittings.
• Use sealer on pipe threads with the tape or sealant starting on the second thread to keep from contaminating the system.
• Keep all lines as far away from heat as possible.
Take a look at the following photos for a few more tips and tricks on plumbing a chassis.
Clausen showed us a neat trick;...
Clausen showed us a neat trick; here he uses a file to make the surfaces around the outlet ports of this master flat so banjo fittings can be installed.
This is a close-up of the...
This is a close-up of the filing operation. Thanks to gravity, none of the filings ended up in the master cylinder.
Here's the finished produ...
Here's the finished product.
Using banjo fittings on the...
Using banjo fittings on the master cylinder can clean up the looks considerably and keep the lines tighter to the master cylinder.
Often improperly used, Teflon...
Often improperly used, Teflon tape is great for pipe threads. Note that the first two threads are exposed, and the tape is wrapped so it is "pulled" into the fitting as it is tightened.
When using a flex line in...
When using a flex line in a fuel system, make sure it is compatible with today's fuel. Unless you want to replace rubber lines every two years, the best option is plastic-lined braided hose. Note how this line has some slack in it to prevent putting the ends in tension.
There are all sorts of line...
There are all sorts of line clamps available; we chose the old-school rubber-lined variety.
Pure Choice has a complete...
Pure Choice has a complete line of clamps, including these trick pieces that hold a pair of lines.
Made for You offers the All...
Made for You offers the All Plumb Kit with everything necessary to secure brake and fuel lines, as well as electrical wires and air-conditioning hoses.
Frequently it's necessary...
Frequently it's necessary to install a T in a hydraulic brake system. To make sure our lines were adequately anchored, we used these OEM-style fittings that include a bracket.
To mount the T to the chassis,...
To mount the T to the chassis, the tube frame was drilled and tapped. The T was then secured with a socket head screw.
This is a bulkhead fitting;...
This is a bulkhead fitting; in this case it's used to pass through the firewall. A solid steel line comes from the master cylinder and connects to the inverted flare seat on the front side.
On the backside of the bulkhead...
On the backside of the bulkhead fitting, a flexible AN line will lead to the hydraulic slave cylinder that operates the clutch. The arrangement provides the flexibility needed between the engine/trans and the body/chassis.
While it's not exactly a plumbing...
While it's not exactly a plumbing issue, here is how to make sure an electric fuel pump isn't unnecessarily noisy. Make sure nothing but the bracket touches the frame; we had to space the bracket out with a couple of flat washers to keep the body of the pump from contacting the frame.
There is some debate as to...
There is some debate as to which side of the fuel pump to put the filter. We have a simple solution to that problem. We use a big Fram fuel filter between the tank and the pump. This style filter also acts as a water separator. Note the shut-off valve; it makes it much easier to change filters.
In a maximum effort to keep...
In a maximum effort to keep crud out of our Stromberg 97s, we installed a second fuel filter between the fuel pump and carburetors.
For those who want the latest...
For those who want the latest in braided brake lines with a vintage look, Pure Choice Motorsports offers these stainless hoses with black jackets. They also supplied the brake line tabs and clips.
To attach the -3 AN brake...
To attach the -3 AN brake line to the F-100 wheel cylinders, we used more adapters from Pure Choice. In this case, a crush washer between the adapter and the wheel cylinder provides sealing.
The brake line used to hold...
The brake line used to hold the ends of the flex lines are often welded to the frame in the wrong place. After deciding where they should be, we attached ours with 10-32 button-head screws.
Pure Choice supplied the adapter...
Pure Choice supplied the adapter to allow the use of steel 3/16 inverted flare hard lines with -3 (3/16-inch) AN brake hoses. Note the groove in each for a brake line clip. The brass fittings are called trailer Ts (or branch Ts). They have two female 3/16-inch inverted flare ports and one male 3/16-inch inverted flare connection. The male port supplies the left front brake, the female port connects to the master cylinder, and the other to a line leading to the right front brake.