by Tim Palmer
Having recently purchased a used set of heads recently, I found a common problem with the Corvair's aluminum head. Four out of six holes for the rocker cover bolts were stripped out or appeared to be. Boo Hiss. I hate using Heli-coils. Fortunately I remembered an old trick of running a tap down the full length of the hole. Usually the hole wasn't tapped the full length. Assuming I found enough threads to grip, I then replace the stock bolts with the longest one's I can find that will still allow the cover to tightened.
A bit of Corvair rocker bolts history. 60 through mid year 63 Corvairs used a big Phillips head screws a 1/2“ long to hold the covers on with no springs to spread the load. This didn't work to good. The covers leaked from day one. Mid year in 63 GM changed to hex head bolts and introduced the springs. This was also to be used as a fix for early Corvairs that leaked.
My little trick worked on all the rocker cover holes I had problems with. This also worked for several other sheet attaching bolt holes that appeared to be stripped also.
One final note. Be careful torquing down the bolts. Aluminum does not have the strength of steel. That is why more threads are required in aluminum for the same size bolt.
NOTE: Since this was written I have gone to a different method on none concours cars. I use a piece of all thread rod (1/4”-20NC) with some of the street rod valve cover hold down nuts. I put some Locktite on the rod and then screw it in as far as possible. I then cut the rod so I have plenty of threads for the nut to hold on to. So far this has worked great.