If you’re new to Corvairs, one of the easiest and most important mods you can make to your engine is to block off the “fresh air” vent on the engine shroud.
Back when the Corvair was a new car, having mixed air was akin to modern climate control in your daily driver. If it was cool out, mixed air (fresh from the top of the engine) and the heat from the bottom of the engine would mix for a comfortable cabin temperature.
What wasn’t foreseen and what many Corvair owners have learned over the years is that cool air that would normally go over the cylinder head would escape through that vent causing the #5 cylinder to overheat and the valve seat to fail. A “dropped” valve seat is common parlance in Corvair circles.
Here is a very good video showing a dropped valve seat from Auto Anatomy
For this modification, you will need a drill, a sharpie, a pair of tin snips, and a piece of thin sheet metal. A cut and flattened soda can works! You can also buy one herefrom Clarks Corvair Parts.
Remove the “fresh air” hose that goes from the top of your engine shroud and into the firewall. Where the hose fitting comes out of the engine shroud, there are three small hex screws. Remove those and remove the fitting. Lay the flat side of the hose fitting over your piece of metal and trace along the outer perimeter of the fitting including the screw holes. Cut the metal, drill the holes and test the fit.
It should look like this:
You may want to put a very thin bead of silicone around the edges to prevent air loss, but the block off you just made will keep 99% of the cool air going to the cylinder head where it belongs!
Congrats! You just made a simple repair to your Corvair engine that may save you thousands of dollars down the road!
Do you have a story about a dropped valve seat? Have you made this repair? Have a tech tip you want to share? Let us know in the comments or send a message to sfbacorsa@gmail.com.
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