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Old 04-21-2015, 02:00 PM   #163
Michael
 
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Name: Michael
Title: Comp Diesel Sponsor
Status: Not Here
Join Date: Apr 2006
Location: Happy Valley, OR
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Posts: 3,411
Episode 28:

I had a little bit of a side project to complete, as racing season was here and my Vega was no longer making the noise limits at our local track (they got a new sensor system which is apparently more sensitive). I had been running two Dynomax Bullet mufflers per side, but switched to a single large Magnaflow stainless muffler per side, with mounts and 90° ends turned to face each other under the car.

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With some crude testing in my garage using a newly acquired noise meter, it appeared to drop my noise by around 3 - 5 dB, hopefully that is enough!

Next it was time to start the first of many diagonals in the double frame rails:

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After the first couple of diagonals I started "mass producing" them:

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Welding the diagonals in was a bit of a challenge, as I had to have my head way too close to the weld. I tried some reader glasses to help me focus on such close-up items, but they were more hassle than it was worth.

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After way too many hours with my body folded up to where it would fit between tubes, I finally had all of the diagonals fully welded.

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Next up was the start of the firewall support tubing. The "base" for all of this is a big diagonal on the passenger's side firewall, to help counter the torque of the drivetrain as it is transmitted through the mid-plate. This tube intersects a point with several tubes converging, so the notching was a bit difficult:

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This picture doesn't quite do justice to all of the weird contours I had to cut in that tube to eliminate gaps:

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The top side was a more conventional (and much easier) notch, aside from being a pretty steep angle.

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And finally I could weld the other end in with its weird contours:

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Next up was the first of many triangulating tubes coming off this main diagonal:

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Unfortunately as I had tacked this one in I realized that I forgot to drill pressure relief holes! Fortunately another tube would connect across from it, so I was able to drill the pressure relief hole from that point and through both walls of the large diagonal.

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At one point in this notching I realized that my notcher was allowing the notched tube to rotate, despite having the clamp screw so tight that it was deflecting. My solution was to carve a few longitudinal ridges in the clamp, which helped a bunch.

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In the immortal words of Britney Spears, "Oops, I did it again", I managed to forget another set of pressure bleed holes, but fortunately was able to drill across.

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After many more tubing cuts, notches, tack welds, and finish welds I had the passenger's firewall structure complete:

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Now it was time to do the driver's side firewall structure, which has a much different shape due to the opening for the recessed "foot box". This required the first tube to just cantilever out from the upper frame rail at a 90° angle. This was tougher than it looked, getting it positioned just right then holding it while tack welding it (and fighting against the weld draw as the weld cools).

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Now it's starting to get more exciting for me, as I build the area that will surround me as a driver. Needless to say, I'm taking my time and not cutting any corners when it comes to protecting me!
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ISSPRO Engineering Manager
Under Construction: 1999 Chevy Pro Stock Diesel Pickup
LBZ, GT4202R over GT5541R, sponsored by ISSPRO and Chris Alston's Chassisworks
95 F350 CC DRW, Intake, exhaust, chip, injectors, locker, gauges
00 Jetta TDI - tunes, clutch & gauges
And a bunch of gassers
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