I had my 70 LT-1 on a chassis dyno this Summer. Currently, just because I like the look, I have '69 style side exhausts on the car. The horsepower curve went 'flat' at approximately 4500 rpm producing 230 HP at the wheels. A contributor to the results, I'm certain, was that the valve lash was loose, but I'm more curious to know if there is data indicating a reduction in HP when using the factory side pipes. Given the incredible wealth of information in the 'exhaust' department on this forum, I'm hoping for an answer! Thank you.