[lust4speed]

So many variables to consider that it is pretty much impossible to know what RPM the power is going to stop - and seat-of-the-pants is going to lie to you every time. Big cam with mild heads is going to give up way sooner than a moderate cam and well ported heads. My engine in the Cruiser is a very mellow HR cammed 87 octane 400 with some well ported 670 heads. Doug's headers and ported stock cast iron intake manifold round out the system. The engine was put together before the off-shore aftermarket rods were introduced, so it has prepped stock rods with ARP bolts. Two different chassis dyno's several years apart said maximum horsepower was at 5,900 RPM with a fairly flat torque curve leading up to it. That high of number was surprising considering the compression ratio and cam, but the whole system was designed to let the engine breath. You need to think of the performance potential as a chain with total performance limited by any weak links.

Out on the street through the mufflers the Cruiser runs just about as good letting the 200-4R trans shift by itself at 5,200 RPM - even though the dyno only showed a six horsepower loss through my exhaust. You might be making horsepower at an elevated RPM, but that doesn't mean that you might not be just as quick shifting sooner and letting the converter and the engine torque do their thing.