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Exhausted:Build your own pipes 101

November 13, 2011

So i decided that before i drive the car and burn a valve running with no exhaust, i better make some kind of pipe to get the smoke out to the back of the car. I had two exhausts- one from an 84 that i parted months back minus the cat (see scrap yard $$), and the exhaust from the 87 that had some sort of aftermarket cat. Both were totally not race like. After several different set ups on the old Chumpcar 944 i had finally found the best setup sound and power wise so i figured i would start there. I grabbed the 84 exhaust pipes from the attic and hung them under the car, the front pipe attached with a couple of bolts to the header and front hanger, and the rear muffler section hanging on the rear center mount and rear mounts near the bumper. I took out my trusty sawsall and whacked the flange section at the front of the rear pipe off, and ground down the first 1″ or so near the end of each section so i could weld a new piece in there. Now off to the parts store.

For the sake of the budget and most bang for the buck im piecing the exhaust back together with small pieces of exhaust pipe available at Autozone and a Thrush “cherry bomb” muffler which is straight through, muffles the sound but keeps that awsome growl so people know you’re in a real race car. I purchased two 18″ sections of 2 1/4″ ID pipe, one section of 2 1/2″ ID pipe and a 25″ long 2 1/4″ ID  Thrush muffler.  Both 2 1/4″ sections go in the center to replace the catalytic converter – one of the pieces had an expansion at both ends and the other only had the expansion at one end- *expansion- where the pipe is bumped out larger to fit over another pipe. I fit these two pipes together, put them onto the front section of pipe  and then trimmed the rear section to fit this length. Then i tack welded all four pipes together so it can be removed and finish welded out from under the car. Then i moved to the rear of the car. Once again the sawsall came out and i cut the muffler off as close to the rear as possible, leaving a 45 degree slash cut on the back of this pipe. Then i cut the support bracket from the old muffler which fits the hanger on the back of the car, and welded the 2 1/2″ pipe to one end of the muffler which will be my tail pipe. This larger rear pipe gives an aggressive look and a slightly lower tone. Then i placed the muffler into position with the flange onto the pipe which has the slash cut- this means that the pipe will not be very far inside of the muffler but once welded will be plenty strong. I held the pipe in position and marked the muffler where the rear brace will need to be installed to mount onto the hangers near the rear bumper. Then i trimmed the inside of the bracket so it fits snug around the diameter of the muffler, ground down the paint in this area and welded this on. Then the muffler can be hung on the hangers and slipped slightly onto the exhaust pipe and once again tack welded.

At this point the pipes are secure with about three nice sized welds on each joint so the pipes will not bend or turn once the exhaust is removed. Any pipes that would move around can cause mis-fitment or rattles and contact with the undercarriage once re-installed. Then the exhaust is dropped out and slid out from under the car. Now i finish welded each joint, making sure each joint is clean and sanded and welding all the way around each piece, double checking for holes or spots not welded completely. ( I have found that trying to mark each piece and then re-assemble and weld makes for a poor fit so now i weld each piece this way. ) So now i have a full exhaust, no cat and nice flowing/sounding muffler installed which by the way also weighs about half the old muffler and minus the weight of the cat. At this time i took out the sand paper and scuffed up the paint on the muffler and the dirty/rusty oem exhaust. A couple coat hangers make for a nice way to hang an exhaust from the garage ceiling for painting. Thats right. I am trying to make my car not just pretty and clean but also resistant to rust and elements so i am painting the entire exhaust. The header on the car is sprayed black with some 1200 degree spray paint but since it was sprayed over 10 years ago, its very dry and probably wont burn off. The rest however is my problem so i am using some BBQ black paint that i found a few years ago that is brush on and works great as ive used it on a few other exhausts like my old 914 project and the Dragon. After sanding the pipes down i applied a good heavy coat of BBQ black which should be dry by tomorrow when i get back out to the garage. Tomorrow i’ll put on one more coat, allow to dry and then i can rehang the exhaust and fire her up! After that i’ll be a gallon of Swepco trans fluid and two axels away from the car being drivable. Can’t wait!


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