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Old 04-02-2021, 07:34 PM
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TheBandit TheBandit is offline
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Join Date: Jan 2006
Location: Ventura County CA
Posts: 4,654
At this point I had built enough of the tunnel to pull the transmission back out for the remainder of the work. I decided it was important to pull the trans so I could have full access inside to check fitment and eventually paint. The access holes came in very handy for getting to the more difficult bellhousing bolts at the top passenger side of the transmission!

At this point I decided to extend the tunnel cut quite a bit so I would have room to transition the new tunnel back to the original floorpan.

For the final section of the tunnel, I elected once again to use painters tape to establish template and cut with an Xacto knife. Again I marked the tape with centerlines so I could match up dimensions later on.

I transferred the cut masking tape to a recycled piece of poster board that I used for the previous template.

Next I measured and laid out my pattern. I used a large socket to mark out the corner radius I would use for a beading path.

Here is what the flat piece looked like when I did a rough check in the car. Laying it in position helped me eyeball where it would need to be bent. Notice that the front of the piece would need to remain flat while the rear of the piece would need to curve over the existing tunel.

Before doing any forming, I used offset dies to make a relief area in the panel. This is mostly for cosmetic purposes to echo the design of the other tunnel section, but it also stiffens the panel quite a bit.

Then it was time to start forming the part. I try to form from the center outward because any changes at the center of the panel have a big effect at the edges of the panel. I wanted to get the center correct before I try doing the outside features. For this I used a piece of 3" exhaust pipe and I concentrated my hands at just the rear part of the panel, trying to maintain the straight/flat profile at the front part of the panel.

Once things matched up, I clamped the piece and used the same closet dowel I used previously to add a radius bend. This helped me match the profile of the previous tunnel section and bring it back to a point at the rear corner of the panel. Again I bent this by hand, placing one hand on the sheet and one on the back of the closet dowel and working back and forth along the panel in small incremental bends until I got the desired bend angle.

Here is the piece after hand forming. You can see while it is close, the front of the panel does not meet up with the previous panel just yet and the rear of the panel is at the wrong angle to meet the floor.

This is where tipping, flanging, and relief/pie cuts came into play. I started by tipping the rear edge using my offset upper die and polyurethane lower die. The offset die puts pressure on the material to yield it along the line while I and physically pushing upward at the opposite end to bend the flange. Again this takes some iteration.

Not shown, I also added flanges around the perimeter of the piece. I added a pair of Clecos to hold the the piece while I checked fitment. In the photo below, the piece is not fitted correctly just yet. It's sitting low and the flanges are not engaged correctly where the pieces met the tunnel.

Getting this piece to fit to my satisfaction took a bit more love that the previous ones. First I had to pie cut the front corners because I did not have a good method or tools to shrink them. Second, I needed to reposition my flange locations; after fitting it in the car I realized they were off by just enough that I couldn't get the panel to pop into place. So I actually flattened the side flanges back down using a hammer and a backing block, then marked off new flange locations roughtly 1/4" higher on the part and redid the flanges. That bit of rework made all the difference in fit and I was able to install Clecos to hold it in position.

At this point all the metal forming was done and it was beginning to set in that I might not get to play with my bead roller for a while. I took all the Clecos out and brought the pieces out for cleanup.

At about this time, mysterious monoliths started showing up in front of my house.

I primered the panels top and bottom using U-Pol copper weld through primer.

Next I used a Beverly punch to add holes for plug welding. Most areas I attached using plug welds, but some I stitched depending on what made sense for the particular area.

I am really satisfied with the plug welding approach. It was a lot easier for me to pull off than overlap stitch welding or butt welding, although by the time I finished this I felt much more comfortable with tackling those kinds of jobs down the road. To keep things from rusting, I dusted the welds with more copper primer

*I also rattle canned the bottom side of the tunnel with some satin black (still wet in the photo)

With the underside of the tunnel painted, I was able to reinstall the transmission for good.

Now's a good time to show you the shift knob I designed. I sent this design to Twisted Shifterz and they custom engraved it for me. I am kind of curious what percentage of the population would be able to drive my car now that I've done this conversion.

That's all for now. I'll come back and add more thoughts and updates later down the road.

Ongoing 70 Nova build:
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