One of the most common mistakes...
One of the most common mistakes when assembling a motor is bolting up the oil pan without checking for adequate clearance between the oil pump pickup and the pan. SAM recommends between .250- and .375-inch of clearance, and set it at .300 inch on our 461.
A short-block is only as good as the cylinder heads that feed it, and the Edelbrock Performer RPM aluminum castings we bolted to our 461 offer a tremendous improvement in performance over the stock units. They feature 188cc intake ports, stainless steel 2.072/1.680-inch valves, 77cc fast-burn combustion chambers, and thick 5/8-inch decks. Although the ports retain their stock locations, the exhaust port floors have been raised to improve flow. Out of the box, they moved exactly as much air as advertised at 270/180 cfm. That said, one drawback of the factory Oldsmobile cylinder head architecture is its intake port location in relation to the valve angle. While a near-vertical 6-degree valve angle looks great on paper, they yield a sharp transition at the short-turn radius due to the head's relatively low intake port entrance location. By creating a more gradual transition at the short-turn and doing a performance valve job, SAM's students were able to boost airflow to 315/200 cfm. Chevy buffs might contend that so much airflow through a 188cc (before porting) intake runner seems like an awful lot, but there's good reason for this. "With Oldsmobile heads, the distance between the intake port entrance and the valve is very short. This means that the Edelbrock heads pack enough cross-sectional area to support well over 300 cfm of flow despite having a relatively small port volume," Massingill says. "A typical 23-degree small-block Chevy head, which has much longer runners, would need 220-235cc intake ports to flow in this arena. This simply reinforces why cross-sectional area is a more accurate way to gauge a head's flow potential than looking at the intake port volume, and why comparing the port volumes between different cylinder head platforms is a meaningless exercise."
The Olds' COMP Xtreme Energy...
The Olds' COMP Xtreme Energy 240/246-at-.050 hydraulic flat-tappet cam is ground on a tight 110-degree LSA, and boasts .541/.544-inch lift. Order up PN SK42-225-4 from Summit, and you'll get a set of lifters and a double-roller timing set as part of a bundled kit for $250.
When it came time to select an intake manifold, conventional wisdom steered us toward an Edelbrock dual-plane design, however, the Olds gurus at Mondello Performance quickly corrected our errant path. Per the advice of Mondello's Lynn Welfringer, we opted for a single-plane Edelbrock Torker intake instead. "Oldsmobile motors are funny because they don't really make any more torque with a dual-plane manifold," he says. "An out-of-the-box Torker will actually do 12-13 numbers better in hp and torque than with a dual-plane. Our custom intake porting adds another 10 hp over that, for a total of 23 hp over a dual-plane. It's pretty amazing how well the Torker performs considering it was designed more than 30 years ago."
In keeping with our theme of simplicity and low cost, we skipped on the roller cam option and went with a COMP 240/246-at-.050 hydraulic flat-tappet stick. Although its less aggressive ramps most certainly give up some performance throughout the lift curve, we felt the rest of our engine package was good enough to compensate for it. In a 10.44:1 compression 461ci big-block, the cam's duration specs offered the rpm range we sought while preserving around-town streetability. Furthermore, the cam's .541/.544-inch valve lift allows retaining the valvesprings that came equipped on the Edelbrock heads, further reducing costs.
Hitting the Pump
With a Holley 750-cfm 4150 carb bolted to the intake, and 93-octane pump gas flowing through the fuel lines, the 461 was ready to run. After warming the oil and water temperature up to operating range, the 461 belted out more than 500 hp and 500 lb-ft on the first pull. SAM's students and instructors achieved a maximum output of 514 hp at 5,500 rpm and 540 lb-ft of torque at 4,100 to 4,600 rpm with 91 carb jets and 32 degrees of timing. This exceeded our expectations by 14 hp and 15 lb-ft, but what was most surprising was the shape of the torque curve. More closely resembling a plateau than a peak, the 461's stout low and midrange torque will certainly help our heavy A-body Cutlass rocket out of the procession of low-speed corners it will encounter on the autocross.
The factory 455 rockers are...
The factory 455 rockers are marginal even in a mild build such as ours, so we ordered a set of 1.6:1 roller rockers from COMP Cams. They're built from a rugged aluminum alloy rated at 80,000-psi tensile strength, and their needle bearing trunnions can handle in excess of 350 pounds of open valvespring pressure.
The Edelbrock Performer RPM...
The Edelbrock Performer RPM heads come equipped with 1.460-inch springs that can handle up to .575 lift. They actuate 2.072/1.680-inch stainless steel valves.
Since an engine's crankshaft,...
Since an engine's crankshaft, camshaft, timing chain, and timing gears are manufactured to their own tolerances, degreeing a camshaft is an essential step in any performance engine build. This ensures that the cam is phased correctly in relation to the crankshaft. SAM students set our cam at a 109-degree installed centerline.