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.