The 20-Valve 4AGE replaced the 4AGZE Supercharged engines. Just like the early and late 16 Valve 4Ges, they also underwent revisions. The Silver Top was introduced in the CorollaAE101 (1992), and the Black Top in the Corolla AE111 (1997). Both engines used Toyota’s version of Variable cam timing- VVT. Bore and stroke remained as in the original 1st and 2nd Generation 4AGEs(early) big port (TVIS) and (late) small port (non-TVIS). Similarly compression was upped in the later models. The blocks are identical to the late model AE92 generation blocks (and naturally theSC blocks too).
The 20-Valve engines never came officially into the US (and many other foreign markets where the old 4AGEs were available- and of course it imparts a very exotic presence. Theindividual throttle bodies look like they came off the fabulous 503 race engines. Think about it, no Toyota factory RACE Engine had 5 valves per cylinder!! Yamaha- who works with Toyota on cylinder headdesign (and manufacturing), have been a very avid pioneer and supporter of the 5-valve design. The short-lived Yamaha Formula 1 engines had 5 valves per cylinder. In terms of maximum valve to surfacearea- the 5 valve design cannot be beat- theoretically and geometrically.
Aside from the obvious 5-valve and variable timing cylinder head design- the difference from the 4-valve is the dramaticallyreduced weight of the internal components. Pistons, connecting rods, and to a lesser degree, crankshafts have all been updated with lighter weight design. The good news is that it remained an ironblock- the engines were still on solid foundation for heavy and serious modifications.
Between the Silver and Black top- the later Black models came with still lighter rotating components. Layingout the engine components side by side…there are miniscule differences, Toyota was tuning the engines to a higher degree by rotational mass reduction, a lesson advanced from the earlier lightweight...