'In the October '00 issue, CC built an Olds engine ("455 Buildup: New Life for an Olds Engine"). That was a fairly typical build for the day based on a 455 and sporting Edelbrock heads. The basic idea was to show the type of power one could expect when assembling what was essentially a stock short-block with the then-new aftermarket heads along with a dual-plane and a streetable hydraulic cam. It made 460 hp with the tame cam a dual-plane, and nearly 500 later with more cam and a single-plane. A nice package, but not exactly a revolutionary combination.
Then, while shooting last month's cover at Westside Performance in Santa Monica-an old-school speed shop that's been under our noses for the past three decades-we spotted a bright red Olds big-block in the shop that appeared to be our 455's twin with its Edelbrock heads and Performer intake. Proprietor Ted Toki informed us that this was actually a more unorthodox approach to Olds power, using a 425 short-block with aftermarket rods and custom pistons, along with the Edelbrock hardware we'd started with. Opportunists that we are, we figured we could con the Westside guys to haul the red Rocket to our usual testing facility for some flogging and tuning.
The StrategySo why not just use a 455 and go for the extra cubes? Ted has his reasons. Primarily, he favors the 425's shorter stroke and the resulting over-square bore/stroke relationship it yields. This is in contrast to the 455's under-square arrangement, where the stroke is actually larger than the bore. Ted feels that if the goal is to build horsepower, the bore should be large in relation to the stroke for optimum cylinder filling, particularly when using street-oriented out-of-the-box cylinder heads.
Another advantage of the 425 is its extra-long connecting rods-nearly 7 inches from the factory. Ted intended to use aftermarket rods but didn't want to have to resort to radically altered piston designs for this street engine just to accommodate a long rod. In the end they used 7.100-inch Scat H-beams spec'd for a big-block Chevy to replace the stock 6.998-inch Olds I-beams. This necessitated turning the rod journals on the stock crank-a factory-forged steel unit unique to 425s-from the Olds 2.50-inch to the BBC's 2.100-inch. Custom Ross flat-top pistons with BBC 0.990-inch pins make up the difference and utilize a modern 11/416-11/416-31/416-inch ring package for reduced drag without sacrificing seal. The resulting compression with the 77cc Edelbrock heads is 10.25:1; as a bonus, each piston/rod/pin assembly shaves nearly 250 grams over the stock stuff.
Ted cautioned that the only real flaw with the combo was the issue of actually finding a 425, but Westside customer Navid Vahedi scored a complete standard-bore '67 425 on eBay for a mere $300.
After machining, the 425 was assembled using ARP fasteners, out-of-the-box Edelbrock Olds heads, an Isky 280 Mega-Hydraulic cam (232/232 duration at 0.050, 0.517/0.517-inch lift, 108-degree lobe separation angle), and an Edelbrock Performer intake.
At The DynoWestside's Jeremy White brought the 425-turned-433 to Westech for the thrash along with an anxious Navid, there to witness the moment of truth when his first engine build would see fire. The Olds initially ran with an MSD Billet Plus electronic distributor and an Edelbrock 850-cfm Quadrajet carb, which Ted favors for street BOP engines. Navid also brought the 131/44-inch Hooker headers that would eventually be installed in his Cutlass, which fed a pair of 3-inch tubes mounting Flowmaster mufflers.