Shes's So Great, My 408!
pg 2

The Build

Engine assembly mirrors that of the LS1. In fact, almost all of the parts, with the exception of the windage tray and oil pan pick-up, will carry over from that engine. With the 4.00-inch stroke, it is mandatory that the bottom of the skirt on the number 8 cylinder be clearance for the reluctor ring (see photo). Mock up that cylinder and put clay on the bottom of the piston verify sufficient clearance. Before you buy the pistons, make certain that the manufacturer is aware of the 4.00-inch stroke. The block for this exercise had a 4.300-inch bore combined with a 4.00-inch stroke and the main bore housing was align-honed to GM spec (2.750 to 2.751 inches).

Be sure to inspect the cam bearing in the block before you install the stick. There are two possible options. Although Clevite offers a replacement for the standard-size cam bore, some blocks have oversize bearings, and a lot of iron-block 6.0Ls fell into this category. Though the OD is different, the ID is exactly the same, so regardless of which block you have the cam will fit and function perfectly.

The cylinder heads for this engine were CNC-ported and fitted with 2.08-inch intake and 1.60-inch exhaust valves (2.00/1.55 stock) as well as Comp Cams 978 valve springs, titanium retainers, bronze guides, and Teflon™ valve-stem seals. A 71cc combustion chamber and flat-top pistons yielded a compression ratio of 11.3:1, but still tolerable of 93 octane fuel.

The Proof

Baseline numbers were wrought with 28 degrees of timing and 40lb/hr injectors. The yield was 516hp at 5,000rpm and 544lb-ft of torque at 4,800rpm. Leaning out the stoichiometric to 12.4, the numbers jumped to 582hp at 6,300 and 551lb-ft at 4,800. With 30 degrees of timing, it grabbed 592hp at 6,400rpm and 553lb-ft of torque at 4,800rpm. This engine produced more than 500hp from 4,800 to the 6,500rpm limiter and more than 500lb-ft from 3,900-6,200rpm.

PARTS

• ARP main studs (PN 234-5608)
• ARP L-19 head studs
• Federal-Mogul main bearings (PN 152M)
• Clevite connecting rod bearings (PN CB663H)
• Callies Performance Products LS1-specific on-center connecting rods (PN CED2)
• Callies 4.00-inch-stroke LS1 crankshaft
• Diamond pistons (PN 11521)
• Diamond Pro-Select ring set (PN 09154030)
• Comp Cams hydraulic roller (244/248 deg. duration at 0.05-inch, 0.613/0.615 inch lift on                                                   114 LSA)
• Comp Cams R-Series lifters (PN 875-16)
• Trend 7.475-inch pushrods
• Yella Terra 1.7:1 rocker arms
• GM MLS steel 6.0L head gaskets (PN 121575392)
• 6.0L CNC-ported cylinder heads
• GM LS6 intake manifold (PN 88894339)
• Siemans 40lb/hr fuel injectors

FLOW NUMBERS

            Lift             Intake cfm             Exhaust cfm

            0.100             74.7                       62.0

            0.200             153.2                     110.4

            0.300             216.6                    155.5              

            0.400             264.6                     191.3

            0.500             309.6                     219.6

            0.600             327.4                     233.3

            0.700             328.5                     237.6