Well the time has finally come to do something I have been looking forward to for a long time….the exhaust. I am fascinated by exhaust systems. They are a sometimes complex combination of fluid dynamics and acoustics. Done right, they can sound amazing, however they can also sound awful. Hopefully mine is the former!
I bought a box of assorted 2 1/4″ mild steel mandrel bends and a couple of flex bellows from ECS Engines website. I bought the main mufflers some time ago – a pair of 2 1/4″ Hooker Maximum Flow units. My plan of attack was to use the mandrel bends and straight pipe to build the exhaust by butt welding the sections together using my MIG welder. I also plan on adding a 2″ balance pipe to help with overall efficiency and also the sound – a balance pipe take away the bark and make the exhaust more mellow.
To get started, I attached the flange for the right hand bank to a flex joint using a short piece of pipe. I had to keep it as short as possible, but still leave enough room to get the bolts on to the studs.
Once I tacked it all into place I took a 125 degree bend and adjusted the length to tuck it up close to the chassis.
The 125 degree bend was too tight, however this can be adjusted. The old exhaust system ran right in front of the idler arm grease nipple and prevented access, so I was mindful that I needed to keep clear of this.
I cut the 125 degree bend so I would be able to rotate it to achieve the correct exit angle, parallel to the body of the car. The cut off wheel leaves a large burr on the inside and the outside of the pipe. The outside can easily be dealt with using a bench grinder, however the inside burr needed to also be removed. I used the end of a broken file to remove the burr. Files are nice and hard, and the 90 degree edge ensures that it doesn’t dig in.
Once the pipe was cleaned up I put it back on the car and rotated it until the angle was right, and used a felt tip marker to mark the alignment. I then tacked it in place using my MIG welder.
Once the downpipe was sorted I started working on the rest of the pipe back to the muffler. The stands I made last week came in real handy – real glad I made 4 of them as 2 would not have been enough.
I bought a really cool adjustable pipe clamp which has vee blocks to align the pipes. I used these to help line everything up and then marked the pipes with a felt tip marker. I could then take them back to the bench for tacking.
Once the front pipe was done I set up the muffler and started to work on the pipe behind the muffler, following the same process. The trick is to be patient, and tack everything as it is easy to undo with a bench grinder. I only had to remove the welds and re-tack a couple of times.
By Saturday evening I had the pipework sorted up to where the pipe goes through the chassis. I welded on the mounting points, but still left everything tacked for now.
Sunday was a busy day, so I only got started at about 4:30pm. I first removed the existing rear exhaust pipes before starting on the left hand bank. The shape of the left hand downpipe is quite different, so I went trough the same process to tack it together. I ended up with the front pipe up to the muffler before it got too dark to work.
For anyone wondering what a mandrel bend is, it is a pipe bend where the cross sectional area is maintained through the bend by using a steel mandrel on the inside of the pipe while bending it. This ensures a more constant velocity and flow rate throughout the pipe. Most exhaust shops use press benders for their pipes as they are quick and easy however this crushes the pipe through the bend and reduces the cross sectional area. The following picture describes the difference much better than my words. You can see where the original pipe is crushed around the radius.
I spent some time working out what bends I need to get the exhaust over the differential to the back of the car. While I was doing this I noticed that the real seals were still leaking as there was oil on the back of the brake backing plates. I took the differential oil plug out and found that I had over filled it, but I am not sure this was the cause. I will have to remove an axle and see if it is the O rings or the seal in the bearing which is leaking. 😦
I will order the additional bends this week from ECS Engines again. Their bends are good quality and their service is great also. I also bought a pair of stainless hot dog resonators for the rear to complete the system. The plan is to have a system which is pretty quiet, but with a nice deep note.
The one thing I wish I had access to is a hoist….doing this on ramps on the ground is definitely more difficult.
Plenty of work to go, but I am pleased with the results so far.