409 Chevy Engine - 481-Inch 409 Stroker

A Cloyes True Roller timing set (PN 9-3101) drives the cam while a Pioneer cam-bolt lock plate prevents fastener trouble. By bending only one of the two lock tabs against each cam bolt, you can use the plate twice. The Manley thrust button in the center of the top gear keeps the cam lobes and roller lifters aligned.

While several 348 and 409 head castings were offered between 1958 and 1965, ours are casting number 3814690, the top-dog big-port goodies used on the L80 425hp dual-quad 409. The only thing better are ultrarare Z-11 castings. The nearly flat cylinder-head surface is a shocking sight. The seesaw valve layout yields short intake- and exhaust-port lengths. Each complete head weighs 62 pounds. By contrast, a typical iron small-block head weighs about 42 pounds. Notice the six head-bolt holes around each cylinder location. Chevy small- and big-blocks have five-the Gen III LS series only has four.

Though stock 409 valves are healthy at 2.203/1.734, big-block Chevy stainless valves are a direct drop-in once the seats are enlarged. Large 2.250-intake valves boost intake flow while 454-sized 1.725 exhaust valves are slightly smaller but can be had off the shelf. The Chevy SAE report on the 348/409 says the valve heads and spark plugs were sunk into the shallow troughs solely to protect them from damage during assembly and service. The recess adds 12.2 cc to combustion-chamber volume.

The intake ports resemble giant-size small-block stuff. They measure 2.54 x 1.38 inches after a thorough porting job and gasket match. Note the 11/48-inch holes in the rocker-stud towers. That's where factory-issue rocker-stud pins once lived. Now the studs are of the stronger screw-in variety.

Superior's Randy Guthrie flowed the heads on the SuperFlow SF-600 and recorded a very impressive 300.1/235.7 cfm at 0.600 (202.6/154.4 cfm at 0.300). The 76 percent I/E flow ratio is just about ideal. There's no doubt that with decent porting, the L80 409 head can support over 600 hp and hold its own against any competing cast-iron OE head design.

Even after milling 0.030 inch off the tops of the 11.5:1 TRW pistons (before they got coated), the compression ratio was still too high for modern 91-octane pump-gas compatibility. So a set of 0.030-inch Innovative steel shims accompany the 0.045-inch Best #638 composite head gaskets to add an extra 20.63 cc of combustion-chamber volume. The net result is a 0.99-point drop in compression ratio for a total of 10.06:1. The extra 72 cubes more than make up for the 1.5-point compression drop.

Though it was not yet available when the 409 was a new engine, today we can upgrade to a big-block oil pump for vastly improved oil delivery. Note the difference in the size of the spur gears of the Melling M-99HV-S pump bolted to the engine versus the small-block pump (in hand). The big-block pump takes a Melling 241S 31/44-inch pickup tube; the small-block pickup tube is a puny 51/48-inch affair. Also included is a Melling IS-77 hardened-steel intermediate shaft featuring a steel collar at the oil pump end. It all fits inside the stock 409-specific six-quart oil pan.

The 409 block uses cartridge-type oil filters. The only hassle is mess from spillage during service. An alternative is to use a Chevy adapter (left) that fits modern spin-on filters. We'll keep the OE setup, as it looks correct and holds more oil. The filter element is a Wix 51143.

Here's a sight that would have made Dyno Don a happy man back in 1962. Isky solid roller lifters are basic big-block Chevy items with 409-specific tie-bars. Dig those massive intake ports. Manton 31/48-inch-diameter pushrods measure 8.750 (I) and 9.275 (E).