Remember 1992, when Chevy raved about the Gen II’s reverse-flow cooling? Well, reverse is, apparently, out. The new engine uses conventional pushrod V8 cooling. Coolant is pumped into the block, around the cylinders, up into the heads, then out to the radiator. The reason Gen II went reverse was that, to make the power Corvette Development wanted; it had to have a higher compression ratio (LT1, 10.2:1; LT4, 10.8:1). Higher compression made for detonation. The cooling system was revised to run the cylinder heads cooler as an antidetonant strategy, and to run the cylinder bores hotter for higher oil temperature and less friction. Clearly, reverse-flow cooling, the publicity darling of the Gen II engine, was really nothing more than a fix that allowed the limited cooling of the old Small-Block head to work with the higher compression necessary to reach the 300 horsepower level.

Air in the cooling system becomes problematic if it gets into the water passages surrounding the combustion chambers. This often causes localized boiling and that, in turn, allows hot spots to develop on chamber walls and they cause detonation. The problem with reverse flow is that with coolant flowing downward and air bubbles flowing upward; keeping air out of the Gen II cooling system was difficult.

Though the LS1 has a lower static compression ratio; its cylinder heads have improved combustion chamber design and intake ports that breathe better. Those features allow them to make more power. The clean-sheet-of-paper approach also allowed design of the cooling passages around the chambers to be more efficient such that the engine can put out more power than the Gen II but yet have coolant flow in the conventional direction to eliminate problems with aeration. With a better combustion chamber and water jacket design and improved antifriction technology in the block, pistons and rings; it made sense to go back to the normal-flow cooling system.