He also pointed out that if you tried to adjust the manifold upward to cover the top of the Vortec intake port, the contact surface would be so minimal that it would never seal and now the floor of the port would present a sealing problem. It was a total mismatch!
Tuned-port people in the middle of Vortec head swaps were in a pickle. They had to take their intake to a special shop to weld extra aluminum and then mill the surface flat. The costs, not to mention a host of other "quirks" of compatibility we'll show you, defeated their purpose of inexpensive heads, . SDPC cured these problems with their new intake manifold and installation kit.
Ultimately, all this is in the name of power, and boy do the SDPC Vortec TPI base and heads deliver. Using a DTS water brake engine dyno, the Vortec TPI conversion twisted the needle to 305.6 hp, and that was using the stock runners, stock throttle body, a stock L98 cam, 92 octane pump gas, and 15 degrees of base timing. Calculating a 20 percent driveline loss for a 700-R4 transmission, power at the rear wheels is estimated at 244.4 hp. Next up was a combo which added an LT4 Hot Cam, 1.6 ratio roller rockers, a 52mm throttle body, and Edelbrock High Flow runners. Power swelled to 356.7 hp at a very streetable 4,900 rpm. With a conservative 20 percent driveline loss, that would come out to around 285.3 rearwheel horsepower. Now that's what we call affordable bolt-on power!