Cadillac Exhaust System

It’s always enjoyable building functional art and in this case it’s a Cadillac exhaust system built for a straight up show car.   The requirements for this project are:

• everything must be 304 stainless steel
• everything must be tucked tightly to the underside of the car as it can lay on the ground (has bags)
• all welds must be blended and not visible
• must be polished

And that’s it!  Working with raw materials and getting it to this level of quality takes a considerable amount of time.  Building a stainless exhaust alone requires the material to be TIG welded, properly backpurged and with the additional requirement of blending the welds, sanding and the final polishing.

The Cadillac was dropped off with a donor floor pan on it, many mock up parts and a simple primed frame.  This allowed a clean slate to allow fitting this 2″ tubing as tight as possible to the underside of the car and snaking it through the rear axle area.  First off we unload all our materials to begin!

Second was unloading the car off the flat deck and onto the hoist.  We had to get a bit creative as the rolling chassis didn’t have any springs in place and only had wood blocks to keep the wheels from rubbing and the rails from completely dropping to the floor.

Fabrication

This system was built in four separate sections to allow for easy assembly/disassembly.  Below are a few photos of the hours of mock up, tacking, welding and blending process.

Take special note at the Kapton tape on the flex section.  This is for two purposes, one to protect the woven stainless steel from arcing while tacking/welding and also eliminating snags and potential damage during sanding/polishing.

Since the exhaust is tucked so tight there has to be minimal movement, one mounting location the exhaust will be hard mounted to is this bushing location.  First a cardboard template is made and then it is CNC cut on the plasma table, and then welded on.  With the CNC cutting the hole is slotted to allow for some wiggle room during installation.

Note the existing hole right just above the rear exhaust tip.  That hole was already existing, instead of drilling new holes along the frame that hole was used (along with a necessary one drilled adjacent to it) to allow for securing the rear of the exhaust.

Prepping the rear section for final welding.  Kapton tape used to ensure no air is brought inside the tubing during purging, and also to reduce the waste of argon.  Kaptop tape has a decent temperature rating, so if it’s close to another weld and gets a bit warm, when it’s removed it doesn’t leave any adhesive behind.  This saves time having to clean up adhesive residue and just allows us to get on with welding right away.

Once the welding was completed the tip was polished prior to the hanger being welded on.  Once the hanger is installed it is very difficult to polish the pipe, so all the hanger sections have to be pre-polished prior to the hangers being welded on.  Then the area is protected and ultimately repolished when the rest of the exhaust system is polished.

And welded on.  The hanger was also CNC cut and is slotted to allow for some movement during installation.  The hardware threads into two Rivnuts installed on the frame rail.

One last modification.  Removing a bit of material and welding in a section to allow the pipe to tuck tight enough under the car to allow it to sit on the ground.  Material removal is done with a handheld plasma cutting torch, then the surface is sanded flat and deburred.  The hole is then transferred to a piece of paper and then ultimately to a sheet of stainless that is cut by hand in the bandsaw.  It is welded on with a taller than normal bead to allow for blending.

Once the system is fully welded and all the hangers are on, then the bulk of blending, sanding and polishing comes into play.

Some of the many many belts that were used to sand and polish the tubing.

A neat trick to share.  Spray machinist layout fluid on the tubing in order to see where you have sanded and where there may be small divots in the tubing (you can see one easily in this picture).  the layout fluid is essentially like very thin quick drying spray paint.  However unlike spray paint you can take it off with a remover as well, in this case it was just sanded off.  It’s thin enough that it doesn’t clog the belt even at the finer grit levels.

Not a lot of exhausts get this form of treatment but when you’re building a piece for a show car, it has to shine!  Here’s a picture of the car (courtesy of the owner __dekay__ on Instagram) at the first car show it was entered in:

This car will be insane when it’s completed.  Thanks for looking!