- Corvair of the Month
- Posts: 9343
- Joined: Mon Aug 06, 2012 12:33 pm
- Location: Lake Chatuge Hayesville, NC
If you are installing a stock steel oil pan, check the mating surface to ensure that it is flat and not deformed around the bolt holes. If it is deformed you may be able to correct any flaws with a hammer and backup "dolly" (a block of wood). Select a good gasket, and try a lower torque setting. Use a 3/8" drive inch-pound torque wrench, as a 1/2" drive foot pound torque wrench may not be that accurate at the lower levels.bbodie52 wrote: » Sun Aug 16, 2015 8:25 am
The torque specifications for the oil pan bolts is stated in the 1961 Shop Manual to be 40-60 inch pounds. In the 1965 Corvair Chassis Shop Manual, the specification was increased to 85-105 inch pounds! [The valve rocker cover specs in 1961 were only 30-50 in. lbs., and in 1965 were increased to only 40-60 in. lbs.] The bolt size remained at ¼-20 for all model years, so apparently the GM engineers changed their minds and revised the oil pan torque specifications to reduce oil leaks.
The aluminum casting design [used in aftermarket aluminum cast valve covers and oil pans] should not be subject to the problem with stamped steel pans that can deform and crush into the thick gaskets in the areas directly beneath the bolt holes. When this happens the pressure against the gasket is not distributed evenly, with less pressure against the portions of the gasket between the bolt hole areas. The cast aluminum pan will not crush or deform, so it will tend to distribute pressure more-evenly around the perimeter of the pan to help seal the gasket surfaces. The problem with the Corvair oil pan design is that about four quarts of liquid resides ABOVE the gasket, unlike conventional oil pans that serve as a reservoir with the oil stored below the gasket surfaces. In those oil pans the gasket surface only has to seal against splashing oil, but the Corvair has to seal against continued pressure from a liquid that is constantly trying to find a way to escape — even when the engine is turned off!
Lake Chatuge, North Carolina
1966 Corvair Corsa Convertible