I built my 440 in 91 and it's been refreshed three times, this last time I decided to slow the rpm down and only run it to 6500 instead of 7200 with a cam of 20 degrees less duration. I have no idea of haw many pass's the thing has but we Magnafluxe the block, crank and heads gave it a line bore and new H beam rods just because. The 915 heads got new valves and hardware 2.18/1.81. This refresh was 7k before the dyno time. I've never blown a motor and not looking forward to doing one so I maintain them well, this is part of having a ten second ride.