over the years, i had 3 or 4 318`s and i never broke a main cap. but they were seldom used for racing, mostly street use in the 225 hp and 15 second range (when raced) . they were 318 stock short-blocks dressed with 340 intake and exhaust manifolds, 340 cams, and i tried stock j-heads, and 318 ported and milled heads. only trying to say that a 318 or a 340 built for the street, not racing , would last with these caps. you know as much as i do, that racing means broken parts, no matter the engine build.