Number 3, without delving deeply into the "whys" and the "wherefores" of Production Engine development, a perusal of GM PP's LS3+ crate engines (which are
NOT "Production Engines") reveals one interesting tidbit...
fuel requirements. The LS3-480 hp
requires 92-octane giz-o-line which, if I'm not mistaken, is
NOT available in the Golden State of California. I dare say CA's potential sales would be deemed "important" to any "business case".
Add in the LS3's 6600 rpm limits because of their powdered rods and nodular cranks and you arrive at a conclusion that they are inherently inferior to the metallurgy and engineering present in the LS7, not as rev-able...and NOT as "mystical" as a "427 Camaro".
The LS7, at 505 hp, is a
starting point for those interested in "more". Clearly, these engines (limited by their hypereutectic pistons) are capable of "more"...
much more... Specs follow, as per GM PP (
http://www.gmperformanceparts.com/Pa...jsp?engine=2):
LS 376/480:
Block (P/N 12584727): Cast Aluminum with 6-bolt, cross-bolted main caps
Bore x Stroke (in): 4.06 x 3.62 (103.25 x 92mm)
Camshaft duration (@.050 in): 219 degree intake / 228 degree exhaust
Camshaft type (P/N 88958733): Hydraulic roller
Compression ratio: 10.7:1
Connecting rods (P/N 12617570):
Powdered metal
Crankshaft (P/N 12597569):
Nodular
Cylinder heads (P/N 12598594): LS3 rectangle port; as cast with 68cc chambers
Displacement (cu in): 376 cu in (6.2L)
Maximum recommended RPM:
6600
Recommended fuel:
92 octane
Valve lift (in): .525" intake / .525" exhaust
Valve size (in): 2.16 int / 1.59 exhaust
LS7/505:
Block Part Number (17802854): Cast aluminum w/6-bolt steel main bearing caps
Bore x Stroke (in): 4.125 x 4.00 (104.8 mm x 101.6 mm)
Camshaft Duration: 211 degree intake / 230 degree exhaust
Camshaft lift (in): .591" (15 mm) Intake and Exhaust
Camshaft Part Number: P/N 12571251
Camshaft type: Hydraulic roller
Compression ratio: 11.0:1
Connecting rods Type:
Forged titanium
Crankshaft Part Number 12568819:
Forged steel
Cylinder head Part Number: 12578450
Cylinder head Type: CNC Ported LS7 specific pattern 70 cc CNC combustion chambers
Displacement (cu in): 427 (7.0L)
Maximum rpm:
7000
Pistons Type: Hypereutectic aluminum
Recommended fuel:
91 octane
Valve size (in): 2.20" titanium intake, 1.61" sodium filled exhaust
For those potentially offended by the thoughts (and price) of an LS7-engined 427 Z/28, well, we'll just call it a
"COPO"...