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When installing polished louvers in the side gills of a 1969 car, I stopped, not wanting to mess anything up. The rear-most gills are blocked off and blacked out, which I know is normal. My understanding is that if they were open, then the car's ventilation system wouldn’t work properly. That area of the fender, is where the cowl is closed up, to create a plenum for outside fresh air, to be fed to the interior. Air is drawn in at the base of the windshield, down through the plenum formed in the cowl, and out through the vent ***** in the dash. The first three gills are open to vent hot air out from under the hood. If that fourth vent were open, it would draw the hot under hood air and fumes, from the other three vents, into the interior. Not good.
QUESTIONS:
Drilling holes for the rubber well nuts in the rear gills necessarily means drilling into the plenums that close off the fourth gills. Is that a problem? How is this properly done? Recommendations? Screwing the car up to add unnecessary bits would be really dumb.
Both the aft most and second to aft most lower holes penetrate the plenum area. Once you push in the rubber well nut and install the screw, you have effectively restored the integrity of the plenum chamber.
This picture is of my 69 which had the gill trim factory installed. I placed drill bits in the holes so you can see them.
Thank you. What is the size of the factory holes for the well nuts? They look smaller than I imagined. Are they 3/8 inches? Thanks!
I can slide a 21/64 bit in mine. Keep in mind that I have a small amount of overspray on them so 11/32” is probably closer. Be sure to drill a pilot hole and progressively enlarge to avoid ripping the fiberglass. LIGHTLY smooth the holes with a piece of fine - e.g. 320 - paper wrapped around a smaller bit. Wet the well nut with spit and push in.
Drilling for louvers
