Replacing Copper Lines for Reliability
My 1912 Cadillac has three copper oil lines. My previous research regarding copper oil lines was when I restored the engine compartment of my 1932 Packard. When I received the car, all of the oil and fuel lines were copper. Further research indicated that the finish on these lines should be nickel plating, but the underlying tubing material was unknown. Looking at a lot of older Packards plus other marques of older cars, I saw copper was used quite extensively for these lines. However I also found out that copper is not the ideal material for use on a car because copper will work harden as it is subjected to vibration. It's failure mechanism is then to split. Therefore on my Packard I used steel lines and then had them plated. However the steel lines where a lot more difficult to bend and flare then copper would had been.
I believe copper is still used by a lot of home restorers as it is easy to bend and is the correct material for early cars. However in my opinion the questionable reliability of copper lines precludes me from using them on my vehicles which are regularly driven. This all came to a head a few weeks ago as I was troubleshooting an engine timing issue with my 1912 Cadillac. I had gone on a tour only to come back from the tour meeting place on a flatbed. While troubleshooting, I brushed against one of the oil lines and saw that it had sheared off at the connection to the engine block. Perhaps I was fortunate that I didn't make the tour as even though the oil drip gauge would show oil was being pumped into the engine. In reality it might had not had been pumping oil into the engine because of the line breakage. Remember this car does not have an oil pressure gauge as the lines are not pressurized. Also the previous owner had experience a oil line breakage. So two oil line failures in 5000 miles is not a good track record.
I had remembered reading about a copper alloy tubing in a Restoration magazine called "Skinned Knuckles" that had the easy bendable quality of copper, but did not work harden like copper. Also a fellow HCCA and Packard club member John Koziol, sent an inquiry to Carl King, who is a good friend of John's, outstanding engineer/machinist/mechanic, and a fellow Packard owner in the Seattle area (1930 Packard 740 Roadster). He described a copper nickel alloy tubing he was using for an Auburn restoration.
Doing some further research, I found both John's friend Carl King and the Skinned Knuckles magazine were talking about the same tubing material. The article from Skinned Knuckles can be read here. On the same web site there is an interesting video at the bottom of the page about bending this material and proper double flaring technique.
The tubing is called Cunifer, and it is mostly copper with 10% nickel. It had most of the benefits of copper tubing, but without the problem of work hardening. This material is used quite a bit on European modern cars. You can buy it at Brake and Equipment Warehouse 800-233-4053. It is $3.50 a foot. I received the material, and I easily replaced the three oil lines with this tubing. I used a combination of manual hand bending and using a tubing bender. The color is more of a bronze, but for a non-concours restoration it is a suitable replacement for copper lines. It will also buff easily to a high shine. If I was doing a concours restoration, I would have the lines copper plated after having fitted them to the car. The ease of bending, a reasonable facsimile of a copper color plus the ease of bending and flaring makes this material a must for my car's oil, brake and fuel lines vs. using steel or copper tubing.
Other suggestions were received from club members in regards to using copper tubing. Steve Weber suggested this option. "First is to make up your copper oil lines with all fittings ready to attach to the engine & oiler, then anneal the copper line. This is easily done by heating the line with a propane torch till red hot then quench the line by dropping into a water bath. The copper line will be dull in color after it is chilled but can be polished with brass polish." He has seen lines treat ed this way last for many years of service.
Mark Shaw suggested "making a loop in the line near the connections to absorb the vibrations."