That's shifting too early for a small block. For maximum acceleration you want to shift at a high enough RPM that the RPM after the shift will be very near the torque peak of the engine. Somewhere closer to at least 4,700 RPM is where a stock small block should be upshifting at full throttle with an auto tranny. /forums/images/graemlins/cool.gif With a mild cam the proper shift range can move up into the 5,000-5,500 RPM range.
You need a pretty hot cam and some serious valve springs to make it up to the 7,000 RPM range that PI likes to play in. /forums/images/graemlins/shocked.gif A good balance job is also in order when revving 'em up that high. /forums/images/graemlins/cool.gif