The Rebirth
While the block baked in the hot tank, Howard Allen polished the stock steel crank journals to create a pristine surface finish, checking them with a mic to ensure proper bearing clearances. After separating and cleaning the stock piston/ rod combo, Robert Hendrix ran the rods through a strengthening shot-peening process and lightly blasted the pistons with glass-bead media. Hendrix resized the toughened rods until the Sunnen bore gauge couldn't discern any out- of-round on their big ends. Will Didier assembled each piston/rod set, using a Carrillo rod heater to expand the pin bore for minimal distortion and galling. Since we essentially reused the entire stock rotating assembly (except for bearings and rings) we didn't balance it, hoping that GM's factory spec would work within the confines of a 5,500-rpm redline.
With the short-block renewed, we tore into the cylinder heads. We caught a lucky break, salvaging the stock iron valve guides after a quick knurling operation. Since we saved some cash on this step, we went ahead and had Pete Hillemeyer machine the guides for Teflon PC-type seals that improve oil control. Hillemeyer went to work on the ever-accurate Serdi machine, cutting the three-angle profile into the seats. Sal Alcaraz fixtured the finished castings and cleaned up the deck surfaces with a 0.020-inch cut. We didn't cc the chambers to check how this changed compression, but the change in compression should be minimal. Finally, the stock 2.06/1.72-inch valves were checked for straightness, and any severely pitted valves were replaced with unscathed candidates from JMS' ample inventory of cores. Hendrix ground each valve's seating surface until it had perfect concentricity with its stem, and your author wrapped up the headwork by hand-lapping the valves to the seats.
We'd had our fill of stock parts, so it was time to order the performance equip-ment that would separate our motor from the stock LS5 tune. A modern cam profile, intake, carb, ignition, and oiling system are all you need to extract tire-frying power from any BBC, especially the 454-cube variant. Crane supplied a hydraulic cam and lifter kit-the Powermax 286 keeps duration mild (226/236 at 0.050 inch) and is designed with a wide lobe sepa- ration (112 degrees) for a smooth idle, but it boasts 0.544/0.556 inch of lift to move plenty of air through the combustion chamber. Crane's Mark Campbell spec'd a mild dual valvespring, installed with 0.050-inch-tall retainers to keep the seat pressure around 110 pounds for longevity. Keep in mind that cutting the valve seats changes the installed height of the valve-springs, so please check this spec when you're assembling the heads. Crane's 31/48-inch hardened pushrods were more than adequate to actuate the stamped steel rocker arms-you read that right-using this mild hydraulic cam, stamped long-slot rocker arms suffice. Just be sure to use factory-style valve covers with welded drippers to keep the pivot balls well oiled. Trans-Dapt offers awesome-looking factory-style, non-dripper BBC valve covers if you opt to run roller rockers.
Aftermarket valves were beyond...
Aftermarket valves were beyond the scope of this project. Robert Hendrix marked the hammered sealing surfaces of our stock valves with machinist blue prior to grinding. He ground the valves until a continuous band of metal was machined off the surface, guaranteeing concentricity to the valve stem (and good sealing on the seat).
Using a high-dollar Serdi...
Using a high-dollar Serdi machine, Pete Hillemeyer masterfully cut the iron seats on our stock oval-port castings. Installing hardened inserts wasn't part of our plan; instead we dropped a lead additive to every fifth tank of gas to prevent seat recession.
Back at home, we scrubbed...
Back at home, we scrubbed the oil galleys with diluted Simple Green, using Milodon's tough engine brushes to loosen the stubborn deposits.