More Exhaustion

 

After the last update and the start of the exhaust system I continued with making my slip couplings on the newly fabricated first section. These are made of some slightly larger diameter steel and have been welded on to the two horizontal sections. I initially had two stainless steel slip couplings (clamp on) to attach the pipes together however they were basically dog shit and wouldn’t compress/clamp onto the pipe so they were done away with in favour for these slip couplings. I welded a nut onto each end after drilling a hole through, this will allow a short M8 bolt to nip up through onto the sliding section and stop it sliding out. It’s a relatively good friction fit anyway and will have some exhaust paste on final assembly however prevention is better than cure. 

The next section was to weld a 45 degree angle onto the leading 90 degree leg. This will now direct the exhaust horizontal along parallel with the sill. This is just a case of mocking up on the car and marking accordingly before a few tack welds then checking everything before fully welding together. Just after the 45 degree bend I have also welded an expending cone which goes from the 38mm diameter up to 45mm this is the same as the original spitfire exhaust which in theory should keep the back pressure equal and not restrict the performance. 

It was all coming along quite nicely but the next bit was to notch the secondary down pipe and weld into the primary pipe. Another reason to have the slightly larger diameter pipe just after this join to cope with the increase gas flow. Before I cut this for real I used an off cut of pipe and made a thin cardboard sleeve in order to cut with scissors and practice the angle and cut for a good fit. This was all fairly good fun, and whilst I’m sure there are other ways to calculate these angles as long as I get the end result I’ll be happy with that. I’m no professional fabricator this is all part of the fun of kit car building you have to be a jack of all trades.

So after I was happy with the fit of my practice piece  I simply used masking tape to make a template then transferred it onto the secondary down pipe. And I’m pretty bloody happy with how it turned out. The notch cut was nice and uniform all the way round so will weld up nicely. I marked the circumference of the secondary with a pen so when it was all removed I could see the area I needed to remove before welding up. Then it was out with the grinding disc again and start cutting away. I have sacrificed another Dremel multitool during this project my first one lasted years and years and now I’m lucky if a get one to last 18 months…and I’m not giving them a hard life. 

 Once cut out I filed everything smooth everything was welded into place, after a few tack welds and trial fit first. Then when fully welded I dressed off the top with a flap wheel and then I could make a start on the exhaust wrap. I managed to get 30 meters of exhaust wrap online for only £10 so was happy with that and it’s a nice titanium colour so looks great also. I wrapped the exhaust in two sections first the upper pipes that come off the manifold up to the slip couplings, then the further two pipes as they come out the body and down along the main side pipe up to the edge of the drivers seat access. This should help keep the heat down directly under the carburettor intake filters and also reduce the risk of burning your legs getting in and out the car…. Not that I have ever done that in the Cobra either but it will help soften the blow if it does happen.

I can’t continue any further yet as I’m waiting for two further 90 degree bends to be delivered that have gone AWOL in the post. But when they arrive I will be able to finish the exhaust up to the rear silincer, which will be another custom fabrication idea that I have. I’m really pleased with how this exhaust is looking so far and it will genuinely be exciting to hear what it sounds like when I get the engine running still need to get the carbs built up properly first.