At the top of the engine we find the induction system comprised of an Edelbrock Performer
A stout bottom end and ample compression ratio will provide the right foundation for a stout street performer, but to get the job done you'll need the right combination of power parts, including the cam, heads, and induction. In keeping with the budget-minded theme, the cylinder heads are Pro Comp's affordable aluminum castings, which were ordered with Pro Comp's CNC porting. That was not the end of the story, however, since Henderson reworked the heads with hand-finishing of the ports and chambers, as well as revising the valvejob.
At the valves, Henderson focuses on the exhaust valve configuration. Henderson favors a tulip profile valve form over the conventional nailhead valve. The theory here is that the tulip shape will help the flow quality out of the chamber, but the same valve will cost some flow. Henderson figures the trade-off is worth it, taking other measures with the camshaft, header, and a larger valve diameter to compensate for any flow loss. Both the intake and exhaust valves are Ferrea hollow-stem stainless units, measuring 2.125 and 1.625 inches, respectively.
You may notice the extra purple blocks sandwiched between the original carb metering block
Working those valves is a custom hydraulic-roller camshaft from COMP Cams. As noted above, the cam was designed with extended exhaust duration, which Henderson relates is just the right move when using the tulip exhaust valve. The duration specifications are 246 degrees at .050 on the intake, with 258 degrees on the exhaust. The cam was ground on a wide lobe separation angle of 113.5 degrees. Henderson says: "With the 113.5 LSA, I was trying to create a very wide broad powerband, which seemed to work, but I think I could have used even bigger heads. I kind of went to the conservative side." The cam was tested for the optimal installed centerline, with 4 degrees advance producing the best results. Henderson says: "Retarding the cam took away numbers across the board. I think because it was taking away the dynamic compression ratio, because the intake valve is closing a little later. It liked the advance."
Completing the flow system is an Edelbrock Performer RPM Air-Gap two-plane intake manifold topped with a Holley 830 HP carb. The manifold was deep port matched to the heads, while the intake plenum was modified by adding a 45-degree angle to one side of the divider. Henderson says, "The divider seemed to favor one side, so the angle was cut in to direct the flow." To make the carb adjustments easier and far quicker on the dyno, the metering blocks were fitted with Percy's Adjust-A-Jet system. These auxiliary metering blocks allow the main circuit metering to be adjusted with a simple turn of a screw rather than changing jets. On the exhaust side, a Stan's tri-Y header was selected to improve exhaust scavenging.
At the Engine Masters Challenge, Henderson fielded the Chevy along with teammates Tim Kran
On the dyno at Koffel's Place, the engine proved to deliver prodigious power. A custom ignition curve was programmed into the MSD Digital-7 ignition, coming in with full timing at 2,500 rpm at 34 degrees. At 4,500 rpm a smooth downward sloping retard of 2 degrees was initiated, taking the timing back to 32 degrees by 6,500 rpm. Peak horsepower was found in abundance, with 577 recorded at 6,100 rpm. In terms of raw twist, the 407-cube Chevy delivered bucket loads of torque, hammering out 430 lb-ft at only 2,500 rpm, and rising to a swollen 538 lb-ft by 4,600 rpm. Power and torque like this doesn't just appear by magic-it's the details that make the difference.
The plenum area of the manifold was mildly modified, with the bulk of the work focused on
Handling the exhaust is a set of tri-Y headers from Stan's. Henderson tells us the tri-Y h
MSD components were selected for the ignition system functions, including this Digital 7 c