04-02-2021, 07:40 PM
(This post was last modified: 04-02-2021, 07:44 PM by Bob Culver.)
The original solid pistons were round with the fore and aft sides relieved except for a narrow band so the pistons were free to rock fore and aft in bores to some extent.(some after market ommitted and often emerge scuffed)
Then car pistons were made oval with the thrust dia clearance too small for normal expansion. Heat barrier slits concentrated the heat into the fore and aft direction which had very generos clearance (hence oval piston). The greater conducted heat expands and so pulls the thrust dia smaller under load. Engines can get stiff after stopping. Some makes have cast in steel struts to distort the expansion pattern.
Chev 6 engines had ci pistons into the 1930s, possibly 1950s. Dont know if were contoured.
Then car pistons were made oval with the thrust dia clearance too small for normal expansion. Heat barrier slits concentrated the heat into the fore and aft direction which had very generos clearance (hence oval piston). The greater conducted heat expands and so pulls the thrust dia smaller under load. Engines can get stiff after stopping. Some makes have cast in steel struts to distort the expansion pattern.
Chev 6 engines had ci pistons into the 1930s, possibly 1950s. Dont know if were contoured.