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 Corolla AE101 (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 the SC blocks too).
The individual 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 head design (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 surface area- 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 dramatically reduced 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 iron block- 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. Laying out 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 block design (of the pre-multi-valve engines). The difference in the connecting rods between 16 and 20 valve engines is dramatically surprising. However for purposes of radical modifications a Silver top will probably be a better engine to work with (slightly stouter rod).
In Japan these engines were used in Formula Toyota, a series much like Formula Atlantic where there is only one SPEC engine available to all competitors. The magic of 20-valve is apparent on the ability to attain and sustain a high RPM threshold. The addition of variable cam timing allows the engine to surpass both low-end torque and high RPM horsepower figures of the older 4AGEs. This is the closest to race spec engine Toyota has ever produced.
