Plumbing your car can be a...
Plumbing your car can be a harrowing experience. AN this, NPT that--all these different designations can really add to the confusion. We plumbed our Buick and put it all down here for you.
Steel lines, spring clamps, and generic rubber hose have been the plumbing of choice for automobile manufacturers since the beginning. While these basics will get the car down the road, serious upgrades can quickly start to tax these stock components, leaving you with less than optimum performance. Replacing the stock stuff with aftermarket plumbing can be a little overwhelming, especially after staring at four or five pages of part numbers in a catalog. Proper planning is the key to taking some of the frustration out of any plumbing job. That's not to say the job will be simple; there will always be some obstacle you didn't take into account, especially if it's your first go-round.
Aftermarket plumbing involves AN (stands for Army/Navy) fittings, which were developed by the aerospace industry. Each AN size directly correlates with a specific outside diameter of metal tubing. Each size is listed as -X with the number after the "-" indicating a 1/16-inch increase in size. Therefore, a -3 fitting would be 3/16 inch, -4 would be 1/4 inch, and so on.
If the car will see a lot of street time, then running hard lines for the fuel is suggested. Even braided lines can collapse over time, and a properly routed steel line will last almost forever. Our GS had 3/8-inch line from the factory, but it had been hacked up over the years, so we replaced it along with the return, vapor, and brake lines with prebent lines from Classic Tube.
This is what we used to plumb...
This is what we used to plumb the fuel system, trans cooler, and heater lines. Even after we ordered this, we still had to get more and ended up with leftovers. Request a catalog and sketch it out on paper before making the order.
Going from hard lines to AN fittings and hose can be done two ways: with a hose clamp on bare hose, or the proper way with a tube sleeve, a tube nut, and an AN fitting. There is a trick to it, though, and if not done properly, the fitting will leak. The automotive industry standard flare is 45 degrees. This is the angle of the inside lip of the flare and is what seals against the fitting. All commonly available flaring tools are 45-degree kits. AN fittings, however, require 37-degree flares. Those 8 little degrees can mean the difference between a proper seal and a nasty leak. Finding a 37-degree flare tool might prove to be a little difficult, however, as your local parts store won't carry it. We sourced ours from the Matco truck, and it had to be ordered. (Ed. note: We found a good Ridgid 37-degree flaring tool at toolbarn.com PN 41162 for $102.00--that's a good deal.) A basic single flare is all you need once you have the right AN flaring tool for the job. Double-flaring will only cause the tubing to crack. Stainless, mild steel, copper, and aluminum tubing do not have seams and can be single-flared.
Careful measuring is important, as you don't want to order 25 feet of hose only to end up needing 26. Using a simple drawing of a car and marking out the route for the lines and hoses can greatly simplify the task. For fuel systems, determining the placement of the fuel pump (if using an electric unit) is key. We mounted ours under the car directly in front of the gas tank. For the transmission cooler lines, we routed the hoses through the frame to the TCI tranny cooler. We could have used the cooler in the radiator, but we are also running a loose-stall converter and the stock cooler wouldn't be able to handle the additional heat. The steering and heater core routing didn't change, so just measuring the stock hoses is suitable. If you need to make a sharp turn, figure in an angled fitting, like a 45- or 90-degree, instead of trying to bend the hose. A 3-inch radius is the maximum bend for rubber hose.
We made our own carb fuel...
We made our own carb fuel line using 3/8-inch hard line, two carb adapters, and a -6 T-fitting. Using a length of flexible conduit, we laid out the rear line.
Choosing which components to use depends on your budget and level of performance. Earl's Performance Plumbing offers several different types of fittings and hoses to suit each system's needs. We chose to use the Ano-Tuff hard-anodized fittings that resist corrosion and wear better than the more common red and blue anodizing. We also chose the Pro-Lite 350 hose for the fuel and transmission lines for its light weight and flexibility, while we went with the standard stainless steel AutoFlex hose and Econo-Fit clamps for the heater hoses. We used Swivel-Seal hose ends for most of the fittings, as these ends keep the hose from twisting when assembling the lines in the car--otherwise they can collapse.
Inevitably, once you have all your parts, there will be things that don't fit or you'll need additional fittings. If you order your parts online or from a catalog, you will have to wait for shipping, so keep that in mind when planning your system. Once you have all your lines fit and installed, test each system for leaks before setting out on a road trip.
 The hard line was mated to...  The hard line was mated to the AN fittings using a tube nut and tube sleeve. The end of the tube sleeve is pressed against the end of the tube, which will get a 37-degree single flare, and sealed against the AN fitting. |  AN fittings require a 37-degree...  AN fittings require a 37-degree flare. Buying a 37-degree flare tool at the local parts store is not a simple task. We had to source ours from Matco. |  The finished carb lines look...  The finished carb lines look pretty good and clear everything nicely. |