Hey Ken
I used appropriate sized aluminum tubing for the exhaust. Usually I polish it first with very fine sand paper.
I bend the end to the appropriate angle for the front most header.
It helps while bending to insert some thinner copper wire to mitigate having the tubing collapse and flatten at the bend.
Copper wire can later be removed or trimmed and left in there if it gets too stuck.
I then cut and dress the other straight header pieces to fit the profile of the main tube (angled cut with sanded vertical concave profile) and crazy glue them parallel to the first header piece.
It helps when crazy gluing aluminum to lightly sand it in the glue contact areas first for better adhesion.
I then reinforce the underside with more crazy glue with baking powder sprinkled on it as aluminum to aluminum bond is pretty weak. The baking powder is pretty rock solid once it dries into the glue and won’t be seen much on the underside of the header (unless you’re a bad driver ;^)).
Test fit the exhaust piece in the body opening and add bends as needed in the rest of the length of the exhaust.
Trim to length and I usually gently ream out the tip with a small Phillip’s screw driver to make the pipe look more scale thickness and paint the inside of the pipe black.
I also added a thin aluminum strap cut from a beer can (Guinness in this case) as on the real car and fastened it just below the cockpit with a tiny amount of crazy glue. I used a piece from the bar code as it had a perfectly printed black stripe which added a nice extra strap detail I did not need to paint.
If you prefer a clean exhaust the aluminum can be polished to an almost chrome like finish or you can add further paint detail to represent heated exhaust patina as you may prefer.
I usually use a mixture of mostly clear with red, blue and/or purple and just wash it on gently in light layers near bends and joints in the pipe to add the patina. Oil based paints work best for this but in this case I tried citadel water based which goes on a bit too thick in my opinion.
I then clear coat with future to protect the finish.
Then in this case I added some matte burnt brown/black to the end of the pipe using dry brush technique to add further realism.
Cheers!
Bill’s Muffler and Exhaust Shop
