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Harbor Freight sells a hydraulic tube bender for less than $100. This is the same unit I keep telling people to buy for making your own antisway bars- either tube or solid. It comes with 3 or 4 forming dies. If you're handy enough to use it you can probably make your own special forming die for custom setups (or modify one of the set that's close). Mine is now going on 16 years old, has been used several times and still looks & works like new.

The issue with stainless is that you need a specific wall thickness and alloy in order to bend it smoothly with no crimping and walls collapsing on you. In addition you will need a mandrel bender to do a tight radius.

It is much better and less expensive to buy them already done.

I have the Harbor Freight bender and it was very useful on bending PIPE for my roll bar but it basically destroyed the stainless tubing that I had.

That pipe is an uncommon size. Even a well equipped fabricating shop often will not have the proper sized dies

I would suggest you look into the vast array of different elbows available from the larger silicone hose suppliers, such as ASH or HPS. Why fuss with bending pipe when a $20 silicon hose  can likely solve whatever issues you are facing


Haven't actually tried (or needed) to tweek any ss coolant tubes. But back when I worked in a lab for a living, I worked with thin stainless tubes for gas chromatograph columns by simply filing the tubes with separation media (or dry sand). The stuff essentially becomes a particulate bending mandrel. Then you tape the ends closed so you don't spill too much. After bending  you remove the taped ends and pour the particles out with a little selective tapping.  Damn, that was a loooong time ago.....

As far as using the proper bending dies, I wrap hollow 4130 swaybar tubes with many layers of tightly wound duct tape so it fits snugly in the closest die. Seems to work at the low bending pressures & angles needed.

In order to bend stainless smoothly you need to buy it before it is annealed.

Un-annealed stainless will often flake, so mills don't want to loose stock by it ageing in the unsold racks, and almost immediately anneal it.

Packing the pipes with sand is an old process and still used by some but the problem with it is that you just can't tape the end of the tubes closed. As you bend the tube, you displace the sand, so if you can completely contain it within the tube it has a high percentage of effect from keeping the ss from crimping on the inside of the radius BUT the radius still tends to flaten.

There are a bunch of stainless alloys available but generally speaking it does not like to stretch or compress easily. I'd guess because of the hardness that the chromeum adds to it.

The easiest alloy to work with is 409. That is what is currently used in production automobile exhaust systems and what will turn a redish brown as it oxidizes and it will eventually rust through.

It is not what people commonly think stainless is, i.e., a shinny chrome like looking metal that is relatively impervious to oxidation but will blue like chrome does when exposed to high heat like on stainless headers immediately after the exhaust port of the cylinder head.

You can buy close radius mandrel bent tubes that you need to weld on to the straight tube but then you are getting into the issues of welding stainless and not having the welds crack down the road somewhere.

It might sound like it is easy to work with on the surface, "but it ain't".

THEN, even if you are working with straight TUBING (not pipe) you are going to want to bead it so the hose you clamp on to it won't pop off. Don't even go there.

Last edited by panteradoug

It would be helpful to understand what 'changes' you need to make, are you talking different routing for the already bent tubes and if so how much deviation and how many tubes?

The vendors obviously get them fabricated, will one work with you and their supplier to custom bend to your needs?

We just finished plumbing a car with one of the stainless steel pipe kits and I'll agree there's a couple of things that seem like they could fit better.

The pipes under the car to the front usually work ok, the fun spot is where the two quick 90's turn up to meet the water pump inlet and the long pipe coming down from the base of the swirl tank.

I cut the 90 off the 1 3/4" to 1 3/8"adapter section, and just the 45 off the long pipe down from the swirl tank. The short 90 degree elbow furnished wasn't used.

I am not so keen on the silicone hoses. They require special clamps and on a prior installation I had a lot of trouble with slight weeping of coolant.

With two cuts, one Gates 22147 molded rubber hose replaced three of those ss bends with molded bends that look like they were meant to be there. There is no stress on these connections. They just lay where they should. No forcing, no stretching. And I eliminated a bunch of clamps too. Ended up with about an inch and a half of leftover/wasted rubber hose afterwards.

The other area that just didn't look right was the pipe from the water outlet/thermostat to the swirl tank. It's not parallel to the engine in either the x or y axis. That was pretty easy to fix by cutting and shortening the section of pipe beneath the green stripe hose there in the photo. I let the hose run the length of the straight section of the pipe because it will provide a bit of insulation to the alternator below and wiring that gets routed there.

You will need a beading tool. I got mine from Graham Tool co.

Two Gates 28471 hoses will provide the tight 5/8"  90's coming off the steel heater line nipples. The long tails will be routed/trimmed to meet ball valves and then run on up to their respective homes. I used 1/4" shims to push the firewall electric panel out far enough to run the hoses between it and the firewall. Tidies things up a bit back there.

Good luck.


Images (9)
  • molded hose 1: Under car looking up.
  • molded hose 2: Coming over frame rail
  • molded hose 3: Run to swirl tank
  • molded hose 4: Nice and square now
  • molded hose 5: Water outlet pipe and hose
  • molded hose 6: Graham beader
  • molded hose 7: Cut off SS bits and unused elbow
  • molded hose 8: 1 3/8' dia. Gates 22147 and waste
  • molded hose 9: 5/8" dia Gates 28471 heater elbows
Last edited by larryw

Vendors and private owners have been making undercar water pipes for decades. So not all stainless pumbing 'kits' are the same- and some are not even stainless. Some early ones in the ;70s were thinwall copper, apparently for a little more heat radiation. That turned out to be another un-good addition to Panteras unless you insulate the console!   

For the engine ends of my 20+ yr old stainless tubes, I used 90 degree copper sweat-solder fittings 1-1/2" OD.  Std 1-3/8" gates hoses can be expanded enough with heat to slip on. No leaks in this century.....

@jb1490 posted:

@ larryw:  Keep an eye on that molded hose going to the water pump, as they have been known to collapse from the water pump's suction.  


That is what the 90° is for and why the original molded hose was replaced with a metal elbow.

I got a ss set from Hall and had to do some cutting and rerouting to the expansion tank. It wasn't overly complicated and fits better now.

I used Aeroquip hose for the pipe splices. Silicone will squiggle off and if you choose to use it, you need to get six ply reinforced silicone.

The Aeroquip is stiff. You can't collapse it.

Last edited by panteradoug

I heard about the potential for collapse of rubber hose at the water inlet location sometime after I'd re-plumbed my own car 15 years ago.

I am going to posit that the short amount of ss pipe we remove (4"+/-) for substitution of the molded rubber 90 at the bend, compared to replacing the whole ss water inlet adapter tube (about a foot) with a molded hose is likely why we haven't suffered any troubles. The other two cars we've re-plumbed with ss lines were also done similarly and have not shown any signs of cooling distress over several years of operation either. The photos above are of car 4 receiving attention.

After JBs comment on the issue here, I made a mockup to test this and found it all but impossible to collapse a length of hose between two rigid nipples 4" apart. It can be deformed a bit, but you can't squish it flat.

I'll admit that I don't get her out as often as I used to, (Miss P hasn't been the only horse in the barn for a while now), but 5 HPDE days at the NHMS (200+ miles on track), and 25,000+ road miles later, presumably overheating would be the manifestation of the issue. It hasn't happened. On an hour plus ride on a hot August afternoon in heavy traffic the temp needle will creep up a bit, but that's it. Once moving again, it recovers quickly and she has never barfed a drop of coolant

My cooling system is tight. During assembly I fitted a schraeder valve and a pressure gauge to the engine block temp sender port and charged the whole system. I chased leaks until it would hold 15 PSI overnight. To this day, even after a winter of sitting, when I remove the swirl tank cap it makes nice little sucking noise that confirms it's held a slight vacuum all that time.

YMMV, Good luck.

Last edited by larryw

Biggest problem with molded two-different-end-sizes rad hoses at the water pump is, the gearshift rod usually rubs the hose, since hoses expand and move when full of hot water. The engine also moves on its rubber motor mounts. This was a problem because some early Pantera gearshift rods WORE A HOLE thru the stock hose! Had ZERO to do with collapsing a hose in high speed use.

It was enough of a concern for Ford that a specific metal part with thinner walls than the molded hose, was developed by Ford (D26Y-8290-A) to fix all cars after Chassis #3564. There is a Tech Service Bulletin (TSB #12 article 101) covering this Factory Fix dating back to 1974 when the Pantera was still in production.. I would NOT use any molded hose combination in that area  You're just recreating a known 50-yr-old problem.

Hmmm. Maybe fixing a fifty year old problem?

Not the collapse thing. I'm confident I had mitigated if it was.

It's a routing thing. The way you put things back together when you're doing it for yourself. Attention to clearances at things that may abrade each other. Making sure things 'want' to be as you picture them.

Got that covered too.

SS tube bend at the shift shaft remains with 1/4" plus clear.  I could picture a rubber hose dragging there. But, no modifications to that end of the tube. Its what you get out of the box.


Last edited by larryw

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