April 2025

Because I have chosen the Autobionics 'cool air intake' solution for the LS3, I also had to use their engine mount system to locate the engine further back from the cabin bulkhead to provide sufficient clearance for the air filter and intake pipe.
This creates a challenge with the long tail G50/52 transaxle that I have. If I was to fit the rear grill on the inside of the clip, when selecting first, third, fifth or reverse gears, the linkage would make contact with the grill and push it outwards. Making a clearance hole would look clunky at best. Not fitting the grill makes it look incomplete.

I figure that I need to rebate the grill into the opening. I tape some cardboard to the outside of the opening and with a Sharpie transfer the opening onto it from the inside. Once cut out I trace around it onto some hardboard this enabled me to correct the edges a bit to ensure a good fit in the opening, allowing clearance for the grill thickness using some grill offcuts I had as shims.

Once I was happy with this template, I transferred it to some one inch thick plywood I had. The advantage of this is it is solid enough to dress the grill around all of the edges. The disadvantage of this is it is solid enough to resist bending to recreate the curvature of the rear clip.
I cut another piece of the plywood with a curve that I need and strap the curved surface to the back of the template and apply as much tension as I can. I repeated this several times also soaking the wood and leaving it over night. This does not work very well, to assist it I cut a lot of vertical slots in the back of the template with a skill saw and repeat the water and stretching processes. This helps a lot, although it tends to lose its curve quite quickly so when not using it, I strapped it up again.

Using a dead blow hammer and a hide faced hammer I gradually dress the edge of the grill around the plywood template, at the sharper corners I need to cut out small wedges to get a good edge finish. I was surprised how well the grill material could be shaped without the actual mesh pattern getting damaged. I expect the sides that were dressed with the hammers to collapse and flatten but they did not.

Once I am happy with the fit I use the template to cut out under sized holes for the exhaust tail pipes. The grill was then folded inwards over a pair of aluminium rings that the factory suppled many moons back with the grill kit. I believe now they use a two piece anodized set of rings that clamp onto the grill. If am unhappy with my result using the original method I could still go that way.

To secure the grill I will need to remoe the rear clip and drill, rivet and Sikaflex around the edge from the inside. I am saving that job for another day... :-)