April '20

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30 THE SHOP APRIL 2020 BUILDING THE Nighthawk II LS As a raffle prize at the 2018 PRI Show, this all-black beauty needed to have it all. By Mike Mavrigian APRIL 2020 Vacuum Pumps p.36 Engine Products p.40 PRECISION ENGINE EDITOR'S NOTE: This is the fourth and final installment in a four-part series following the build of a 428-ci, 631-hp GM LS engine that was raffled off at the 2018 PRI Show in Indianapolis. Part I appeared in the July 2019 issue of THE SHOP magazine, Part II in the October 2019 issue and Part III in the January 2020 issue. VALVE COVERS In order to provide adequate rocker arm clearance, I opted for Holley's tall LS valve covers, which not only provide a taller roof but also feature mounting bungs that allow direct installation of the MSD coils without the need for any coil brackets. The valve covers include a set of 6mm x 1.0 x 80mm mounting bolts and aluminum standoff tubes that incorporate the upper rubber seals. While the supplied hex head bolts are certainly adequate, I swapped these out for ARP 12-point stainless bolts. With threads lubed, all were torqued to 106 pound-inches. Sealing was handled with Fel-Pro OE-style silicone seals that secured to the grooves in the valve covers. IGNITION COILS & SPARK PLUGS Our MSD coils (LS2 style) are far more robust and more dependable than OE coils, and their appearance is far superior. These are my go-to coils for an LS build. The coils mount directly to the Holley valve covers with a pair of ARP 6mm x 1.0 x 25mm (ARP 770-1002) screws at each coil. The 72mm bolt hole spacing on the Holley valve covers allows a direct bolt-on without the need for unsightly mounting brackets. 30 THE SHOP APRIL 2020 FINAL INSTALLMENT Limited dyno time and laptop issues left us wanting more during tuning, but we still managed to reach 631 hp at 6,300 rpm—with a somewhat impres- sive torque rating of 563 pound-feet at 4,800 rpm.

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