I built a 340 with KB 243 hyper pistons in 2007. I used a stock bore block and honed it myself. I have driven the motor 26K miles so far and have driven the motor hard and long in Bonneville at 120 mph for miles at a time more than a dozen times. Driven it in 114° temps in Vegas and Reno several times and the motor has the same cranking compression today as when it was new. Nothing wrong with hyper pistons for the street. I wouldn't use them for nitrous or boost.