Thread: C5 gto
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Old 12-14-2010, 11:10 PM
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heinke heinke is offline
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Join Date: Nov 2009
Location: Prescott, AZ
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Default C5 GTO - belly pan

The beauty of a bare chassis is that you don’t have to crawl underneath to work on the bottom. I used my engine hoist to roll it on its side and that made building out the belly pan much, much easier.




I first made paper templates for the large panels and then made them from .050 3003 sheet (still white in these pictures as the protective poly coating hasn't been removed yet). My brother had given me a 4’ wide end roll from a news paper printing plant that’s near to him. I’d recommend news print like this for a cheap source of paper for templates. I used a combination of step roll and 1/2” half round roll to bead roll these belly pan parts. There’s a chassis triangulation member under the half round beads and I was trying to get the belly pan close enough to pop rivet it in place. It mostly worked but I had to use a few shims in a couple of areas. The belly pan edges are hammer formed over the chassis tubes using a rubber dead blow hammer.




The belly pan is completed with a panel down the middle. This panel is attached with nutserts and screws so it can be removed for access. The belly pan is the lowest part of the car and sits about 5 inches off the ground. That leaves no room for exhaust under it. So the exhaust pipes run through the chassis backbone and mufflers are located in the middle of the backbone. After this picture was taken, I took the middle panel to a friend with a punch press and had some oval holes punched in it for air ventilation. I considered louvers but was afraid they just get crush shut on a tall speed bump.

The chassis backbone is covered inside with aluminum similar to the belly pan. It’s bead rolled in a similar fashion for pop riveting to chassis tubes. It was harder to do because of being enclosed. If you’ve ever tried to place sheet metal around triangulated tubes, you know what I mean.

The open space in front of belly pan is where the engine sits. The cross member with holes is used for engine mounts. With this engine setback (front of engine is about 6” behind front wheel center line), the C5 GTO is almost a mid-engine car. The engine is set low with the oil pan bottom just slightly higher than the chassis tubes and belly pan. In addition, the aluminum suspension cradles are clearly visible in this picture. Lower A arms, transverse composite springs, sway bars, and in front the rack & pinion steering all mount on these cradles. In short, they make great unitized suspension modules with four bolt chassis attachment that works great for custom chassis applications like this.
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