Quote:
Originally Posted by Q-ship
You know that the LS3 and the L92 are basicly the same head when it comes to flow? The only difference in the GMPP catalog is that the LS3 has a slight advantage in the amount of lift it can take.
LS3 max lift (as machined from GM) is .570
L92 max lift (as machined from GM) is .510
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...looks to me that the only difference between them are the valve springs and hollow versus solid stem intake valves, otherwise they are the identical head. Heres some specs from GMPP...and look at the flow at .600" lift!!!!
"
12629051
Bare L92 Aluminum 260 15 deg 70 2.165 1.590 L92 Std LS Bolt-down Bare L92 N/S
12629064
Stock L92 Aluminum 260 15 deg 70 2.165 1.590 L92 Std LS Bolt-down Solid stem valves 229
12629063
Stock LS3 Aluminum 260 15 deg 68.4 2.165 1.590 L92 Std LS Bolt-down Hollow/solid 229
12629051
Bare LS3 Aluminum 260 15 deg 70 2.165 1.590 L92 Std LS Bolt-down Bare LS3 N/S"
and......
"12629064
L92 Cylinder Head Assembly (not shown)
• Aluminum performance head
• Fits any LS family engine with 4.000" bore or larger
• 2.165" solid stem intake, and 1.590" solid stem exhaust valves
• .510" max valve lift
• As-cast L92 style intake ports
• D-shaped exhaust ports
• As-cast combustion chambers
Head P/N 12629064 is assembled with the following components:
12627970
Intake Valves 10166344 Valve Spring Retainers
12582719
Exhaust Valves 12482063 Intake Valve Stem Seals
12589774
Valve Springs 12482062 Exhaust Valve Stem Seals
10166345
Valve Locks
L92 Head Flow Data (4.000" Bore):
Lift
0.200" 0.300" 0.400" 0.500" 0.600"
Intake
151 208 256 294 316
Exhaust 111 152 174 183 189
12629063
LS3 Cylinder Head Assembly (not shown)
• Aluminum performance head
• Fits any LS family engine with 4.000" bore or larger
• 2.165" hollow stem intake, and 1.590" solid stem exhaust valves
• .550" max valve lift
• As-cast L92 style intake ports
• D-shaped exhaust ports
• As-cast combustion chambers
• Uses bare head
P/N 12629051"
Heads 12629063 and 88958758 are assembled with the
following components:
12569427
Intake Valves 10166344 Valve Spring Retainers
12582719
Exhaust Valves 12482063 Intake Valve Stem Seals
12625033 Valve Springs 12482062 Exhaust Valve Stem Seals
other technical tidbits on intake vales......
"One way valve suppliers are taking additional weight out of intake (and exhaust) valves today is offering "hollow stem" valves. The valve stem is gun-drilled and micropolished to make it hollow like a pushrod. The drilling is only done in the upper 2/3 of the stem where rigidity is less of a factor than the area just above the valve head. After the stem has been drilled out, a hardened tip is welded onto the top of the stem. The result is a valve that is 20 to 22 percent lighter than a valve with a solid stem.
According to one supplier of hollow stem performance valves, the valves are good for 300 to 350 more rpm with no other modifications (same springs, rockers, pushrods, etc.).
Drilling out the valve stem to lighten the valve obviously sacrifices some strength, so a slightly stronger valve alloy may be used to maintain the same strength as before. One supplier of hollow stem performance valves said the durability of hollow stem valves is not an issue in naturally aspirated performance engines. But he did not recommend using hollow stem valves in turbocharged or supercharged engines, or in engines using nitrous oxide because of the increased heat."
....hollow intake valves and bigger springs allow the higher lift camshaft profile..... and account for the recommended cam lift specifications as listed. The L92 head design is a winner. It can handle .600" intake lift easily, providing there are no piston to valve issues.
...heres more great valve information if you would like to brush up on technical details.......