Wednesday, May 23, 2007

My First Attempt at a Custom Exhaust!

Remember that Schmidt-like urge to rush things I talked about in the last post? Well, the lack of step-by-step pictures in this post are a direct reflection of that urge.

So, why a custom exhaust? Other than stock, very few quality exhaust systems are available for the 75-78 bus. A complete stock system will run into the high hundreds, low thousands - a lot of money for any vehicle's exhaust, let alone an occasional driver. Other systems that are available include eliminator style exhausts (basically a tin can with the right connections) and header/quiet pack systems like the one I installed last year from BugPack.

The advice that was given to me was to get the cheapest thing possible so you don't mind regularly replacing it.

I was still surprised that already this year the exhaust started getting louder, followed by an obvious seam split and burst on the way home from the Michigan show. Thinking back, the quiet pack tip always had an upwards tilt, allowing rain water to get in the muffler (my spring start-up blew a slick of black carbon soup against the garage wall) so they aren't exactly made to last, let alone the support flange tacked in place right on the seam - what a design flaw!

Granted, as per the original plan, I could have picked up another quiet pack muffler for $70 and bolted it on with the four obligatory bolts. However, I don't want to be doing that every year....

So, with about $100 in parts I set out making this monstrosity which I am actually pretty proud of. The mufflers are universal units off the shelf at The Partsman, basically a jobber shop. They had poster with all the different universal mufflers they can provide, so I found the smallest oval, shortest unit with a sufficient offset of the pipes and 1.5" inlet and outlet. They were $25 each.

The lower centre section is the Bugpack manifold cut and rotated. The rest I made up out of off-the-shelf Canadian Tire bends and a bit of creativity.

My first observations after installing it were mostly positive. It has a very nice, quiet exhaust note at idle and at speed. The cans are hidden away in the recesses under the batter trays so all you really see is the twin tailpipes, so I am very happy with the look.

My negative observation was that I didn't account for the moustache bar engine support and I got a lot of vibration between the pipes and the bar. This week I modified the support brackets I engineered into the flanges and lowered the outboard pipes and cans about 3/4 inch, eliminating the problem. I also added a galvanized flange between the left hand manifolds which bolts up to the cooling shroud to support the left hand heater box - something that is missing in the Bugpack design.