Corvair Forum

Can someone tell me why some covers have 4 bolt holes and some have 6

Early Corvairs had 6 bolts and no spreaders and later they eliminated the center bolt hole and added spreaders on the other 4 bolts. Some people drill and tap the center hole on later heads and add the 2 center bolts.

Thanks for the explanation.

Belt AND suspenders!

The four bolt method, combined with the compression "springs" to distribute the tension across the valve covers, seems more than enough. Valve covers are not hard to seal, and they are only sealing against splashing oil collecting and draining through the pushrod tubes. The oil pan is more-difficult, because it is holding back several quarts of oil that reside continuously ABOVE the gasket — even when the engine is not running! Most engines have an oil pan that is shaped like a trough, that holds the bulk of the oil below the gasket mating surfaces. The Corvair engine is unique, because the oil sits above the gasket, and the oil pan is flat. Splashing oil is easier to seal against leakage than holding back a pool of oil that is continuously trying to escape!

Some people mistakenly install the retainer tension springs upside down. They should be installed as shown, so that the bolt in the center applies spring tension t the outer ends — effectively applying spring tension to the outer ends.



The use of acorn nuts on top of the cylinder head nuts helps to protect the stud threads, to prevent rust and corrosion damage that makes it difficult to remove the cylinder heads for maintenance purposes. These nuts are sold by Clark's Corvair Parts for this purpose. The use of a six-point socket instead of a 12-point socket will do a better job of gripping the sometime rusty and soft head nuts, so they won't round off and make head removal very difficult!

We could probably get a government grant to fund testing in order to determine which valve covers are faster, 4 or 6 hole.

They actually raced valve covers at last weekend's classic car show. Pretty cool.

That was very cool. Valve cover racing. Loved it. They needed a longer track.