Ok to all you back yard mechanics, This Vortec subject just drives me nuts. The '96 and newer 4.3 Vortec use Aluminum cylinder heads. But Vortec motors were first introduced by GM in 1988. The name first appeared in 1988 on a 4.3 L V6 that used "vortex technology" to create a vortex inside the cumbustion chamber, creating a better air/fuel mix. Chevy's production 4.3L 90-degree V-6 (V6-90) block is physically similar to a same-vintage 350 small-block V-8 with one important exception: the oiling system. Chevy small-block V-8s have three oil galleries above the camshaft. The central gallery feeds the camshaft and crankshaft bearings, while the two side galleries lubricate the lifters and valvetrain. Production V6-90 engines (including the 4.3) have only two oil galleries. The passenger-side gallery feeds the right bank of lifters, just like the small-block V-8. A large-diameter driver-side gallery feeds both the left lifter bank and the camshaft and crankshaft bearings; it is offset from the lifter bore centerline to allow oil to flow around the lifter bodies. The production V6-90 two-gallery oiling system has proven satisfactory through 7,000 rpm. In 1992, GM introduced a balance shaft on 4.3 engines.
All Vortec V6-90 degree motor use a cast iron block and heads with a 4 in (101.60 mm) bore and 3.48 in (88.39 mm) stroke, both of which are the same as a 350, which gives them a displacement of 262.39 cubic inches (4,299.8 cc). Connecting rods still measure 5.7 in (144.78 mm) although the rod journal diameter is 2.25 in (57.15 mm). 1992 and later cylinder blocks used a different timing cover since these engines used a balance shaft (some 1992 production cylinder blocks for the LB4 with TBI induction used the 'traditional' front timing chain cover from the small block Chevrolet). This change created a situation where most aftermarket timing chain alternatives do not fit. This is true of gear drives and double roller chains
