Quick run-down: Buick V6s were odd-fire (two rods share a common journal) until mid 1977. 1978-up engines are even fire; the rod journal was split 30 degrees to allow an even firing order. Some race builders later ran odd-fire cranks in their Stage motors as the oddfire crank is stronger (especially for stroker cranks where the split pin becomes a thin point).
The Buick racing program got into high gear in the 82-83 time frame; Buick began working on the Stage parts. The Stage 1 and Stage II blocks began production around 84-5; they were heavy duty, race-only versions of the production blocks with a revised, better casting.
The Stage 1 and Stage II share a common casting but differ in finish machining; the Stage 1s are machined the same as production blocks (wet sump, 2 bolt mains, 8 head bolts per side). The Stage IIs got 4 bolt steel mains, relocated pickups and later dry sumps, relocated cam oil galleries, and 14 head bolts.
The split pin for even firing motors resulted in a rod offset in the bore; this "off-center" design carried through for all production V6s. In 1987 at the power levels the Stage blocks were producing, this became a problem and the blocks were revised with shifted bores to eliminate this offset, creating the "on-center" blocks. The on-center blocks carried through into the early 90s with various production revisions including revised rear main oil seal, cross-bolted front and rear mains on later blocks, etc.
Corresponding to the Stage II block was the Stage II head development; this was a fresh design, race-only head. It shares no parts with a production head, requiring a different intake, valves, rockers, headers, valve covers..even the cam is different as the valve layout was revised.
This excellent head was the biggest factor in the success of the Buick V6 in circle track cars; it has a very small, efficient chamber, ports that easily flow 300+ cfm on the intake, and 14 bolts to match the S2 blocks. 274 ci circle track motors with a single 4 bbl carburetor made in excess of 525 hp; twin turbo race Stage IIs have made at least 1400 hp and run 6.90s@200+mph!
For pictures of various blocks, heads, cranks, etc., see
www.gnttype.org and look at the picture guides. OK...I am an insomniac and I need to go to bed now.
