Most of the automobiles manufactured during the 20th Century used tubing in some form for various purposes. Fuel lines, vacuum lines, oil lines, and even water lines may have been fabricated using copper, brass, steel, or aluminum tubing. During a car restoration project, you can expect to have to replace or even fabricate from scratch a line made of metal tubing. In this article we look at fabricating three custom bent tubing lines for an oil filter, a fuel line and water line for a firewall heater. Fabricating tubing lines follows three parameters, the Length of a segment, the Bend Angle, and the Rotation Angle (if any) as shown in Figure 1. Keep these three in mind as you read the article and view the photos. In the case of the existing oil line (Photo 1), the shape and orientation did not seem right, and an inspection of the existing oil line showed portions that were not straight and one section was worn thin (Photo 2). It most certainly would have burst under pressure, so a complete new fabrication was required. The fuel line was also fabricated using an existing pattern, however the water line was a new fabrication.
Figure 1 — Graphic showing the three tubing parameters: 1) Length (of a segment), 2) Bend Angle, and 3) Rotation Angle. Segment Lengths (L) and Bend Angles are straight forward, but in some instances the tubing is rotated making the next bend.
Photo 1 — This length of original copper tubing was examined and found to have a one inch long scrape almost as deep as the thickness of the tubing's wall. Clearly this length of tubing rubbed against something during its life, causing a worn spot on the side of the line. No doubt that under pressure, this tubing would have burst apart.
Photo 2 — Close-up view of the worn section. This length of tubing cannot be trusted and is not worth repairing.
Our inspection of the original oil line showed that it had been modified sometime during its life, so its shape could not be used for an accurate pattern. So a new pattern had to be made. Bending tubing into nearly exact angles and at specific locations can be complicated enough; having a good pattern is essential. Solid copper wire could have been used to create our pattern, however this reusable rubber Twist Tie calledGear Tie (Photo 3) was an even better choice. They are readily available in hardware stores. Originally designed to organize electric extension cords, using it as a tubing pattern worked well.
Photo 3 — Side view of the oil filter mounted against the firewall where this oil line must be connected. The 5/16 flare fitting is at the bottom of the filter and is a important consideration in making this tubing line. Note the orientation between the oil filter and the engine's head. The tubing as it descends from the fitting has to be offset (bent) towards the firewall and then straighten downward before the bend to the flare fitting on the crankcase.
A first step in making this oil line is establishing the route the line will take between fittings. It has to travel around the engine's head, near the firewall and close to the exhaust manifold, and finally bend its way towards the crankcase. Photo 3 shows this path and the small space available for routing the oil line. The flare fitting under the oil filter is our starting point. This permits a length of about two inches before we come to the offset needed to clear the engine head. As the GearTie is much longer than needed and we didn't particularly want to cut it, the excess was rolled onto itself and a bend was placed where it could be wedged into place, keeping the access out of the way while adjustments were made (Photo 4). Photos 5-8 show the GearTie pattern bent into shape and placed against the brass tubing to layout the bends.
Photo 4 — As with most projects where there is some uncertainty, making a pattern helps the fabricator by offering a visual guide that replicates the desired part. In this case a reusable rubber Twist Tie from GearTie (stiff flexible rubber coated wire) was found at the local hardware store. They are intended to wrap electric extension cords, temporally hang things and many other uses. Its ability to be easily bent and retain its shape was the primary factor for using the GearTie for this pattern application and it worked exceptionally well. Note: The GearTie is rolled onto itself because it longer than needed.