I know Comet rates the 40 series at 18 horsepower max, but many people run them far beyond that rating. I see them on built big blocks pushing 30-40 horsepower, Predator 670cc builds which already have 22 horsepower stock, and even on a 60 horsepower Predator 670cc lawn mower. My question is how far past the rating can you reliably go before you start getting belt slip/shredding? Would a 40 series even hold up to a Predator 420cc with a mild cam?