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Oldsmobile 455 Big Block Engine Build - 511-LB-FT, 445HP 455 Rocket Olds

Not Every Street Big-Block Has To Be A Lumpy-Cammed, Tunnel-Rammed Animal, So We Decided To Build A Very Streetable . . .

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Edelbrock Aluminum Heads
Our own flow testing and DMR's experience showed us that the off-the-shelf Edelbrock aluminum Performer RPM heads flow about the same as a set of factory iron C heads. This limited flow is partly due to the requirement that the ports (especially the exhaust) remain in their stock locations. We wanted to improve on the intake flow slightly without spending big bucks for CNC porting, so we tried the classic 30-degree back-cut trick on the Edelbrock valves, which netted a minor flow improvement. The Edelbrock heads measure 77 cc and combined with the 15cc dished KB pistons create a 10.2:1 static compression.

Flow Chart
Edelbrock Performer RPM Olds Aluminum Head
2.07/1.68-inch valves (PN 60519 complete)
77cc chamber
188cc port

VALVE LIFT INTAKE EXHAUST EXHAUST TO INTAKE RESULT

OPEN WITH PIPE INTAKE 30-DEGREE BC (CFM)
(CFM) (CFM) PERCENT (CFM)
0.050 34 25 73 -- --
0.100 70 53 76 70 --
0.200 137 95 69 144 + 7
0.300 195 132 67 206 +11
0.400 234 168 72 246 +12
0.500 240 185 77 237 - 3
0.600 245 194 79 239 - 6

A simple 30-degree back-cut on the Edelbrock intake valves was worth as much as 12 cfm at 0.400-inch valve lift. The production 455 head we tested at 0.400-inch valve lift flowed only 190 cfm. Our modified Edelbrock's amazing 56-cfm flow improvement at 0.400-inch valve lift is a 29 percent gain over the stock heads.

Cam Specs

COMP XE-268-H-10 DURATION DURATION LIFT LOBE

DEGREES DEGREES (INCHES) SEPARATION
(ADVERTISED) (AT 0.050)
Intake 268 224 0.485 110
Exhaust 280 230 0.490

Test Day Edelbrock agreed to help us with the dyno testing, and Edelbrock dyno veteran Curt Hooker bolted our 461ci Rocket to the company's SuperFlow dyno. Before firing the engine, we pressure-lubed it with a homemade tool that really was nothing more than a 6-inch-long Allen bolt. The bolt head is used to spin the hex drive oil pump driveshaft. After properly timing the Performance Distributor D.U.I. HEI distributor, Hooker carefully broke in the Comp flat-tappet camshaft for roughly 20 minutes using Royal Purple's 10W-30 break-in oil.

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