[Alan Roehrich]

James is correct.


However, efficiency in the engine itself makes a considerable difference.

The problem for TBI is that fuel injection, even electronic fuel injection, by itself, makes little difference in efficiency. Put that on top of the old 1973 design truck 454, and you get next to nothing, on a good day.

The advantages of the Vortec system are considerably higher compression, better cylinder head flow, better intake manifold flow, and even a moderate improvement in camshaft design.

Even then, the Vortec left plenty on the table. The cam profile still isn't enough, they moved to non adjustable rockers, the exhaust system is a product of design by cost, not efficiency, and the computer tune is mediocre at best.