***INSTALL UPDATE***

I was at WISR when I noticed the right rear corner of the vent had popped loose. Not a fun feeling watching a part of your car fluttering in the breeze on the front straight. I put a few zip ties through it for peace of mind the rest of the day, but knew a reinstall would be in order. Rivets, a different adhesive, or 3M foam auto tape...

It seemed that a good bead of a silicone adhesive might do the trick, so I reinstalled with GE Silicone II adhesive. Everything went well, let it cure 24 hours and when I gave it the "grab the corner and gently pull" test, it failed. It took less force to pry it up than the urethane adhesive, which didn't give me much hope for it holding up any better or longer than the urethane.

The 3M foam auto tape was used by someone on another forum and seems to be holding up, but it's thickness isn't ideal. I also wanted an install and forget solution and I wasn't convinced any adhesive based solution would do the trick.

So I said F-it and went with the black rivets I had already ordered from McMaster-Carr (part #97526A481; black aluminum rivets; 3/16" diameter; 5/8" head; 0.450" long).





Here's the revised install. Taking into account that the ABS plastic will expand ~ 0.5 cm more than the aluminum hood section of the same span over a 200 degree range (black hood can hit close to 200 deg. F in the summer, if not hotter coming off the track, and I was surprised that ABS has a greater coefficient of thermal expansion than aluminum), I did the following.

Drilled 3/16" holes through the vent, and then placed it in the opening on the hood, marked the holes on the hood and drilled.



Then I enlarged the holes in the vent to 5/16" which allows 1/16" of expansion/contraction in each direction for each hole. Given their spacing, that should be ample room for temperature swings it will experience.



To keep the rivets from clamping the vent down too tightly and defeating the differential hole sizing and ability to expand without buckling, I used a "shim" during the install. Didn't have any thin gauge steel around, so I took a length of plumber strapping and thinned it out slightly on the grinder wheel and took snips to the end to notch it.



Put some tape down to protect the paint during install.



Put a dab or two of silicone on either side of the hole to prevent any vibrating due to the hoped for *slightly* less than tight fit.



Then dropped the vent in place and installed all the rivets. Basically, dropped the rivet in place, slid the shimmer-thingy between the hood and vent, then popped the rivet in and slid the shimmer out.



Finished product:





(Yes, my car is in desperate need of a washing and waxing/buffing/etc...!!)

Impressions--I actually like the look! I was worried it would look a little too "Mad Max" for my tastes, but I was surprised. Believe it or not, the poorly painted rivets (sort of a textured black--not on purpose I'd bet--matches the slightly textured vent better than a smooth black rivet would).

More importantly, this thing is rock solid now. The vent is snugly installed with no movement or vibration while driving. I installed it mid-day, with temps at about 75-78 and bright sun. I'd bet the hood was at least 100 degrees (hot to touch), which is right about the middle of the temperature extremes it should see. I'll update if any buckling occurs, but I think this should do it.