HEAD FLOW COMPARISON
The heads were compared on a JK&M Custom Flow 400-cfm flowbench. Testing was performed at 28 inches of water.
6X Iron HeadKRE Aluminum Head
LiftIntakeExhaustIntakeExhaust
.10088859271
.200153122166129
.300206164234169
.400221185256201
.500232196261220
DYNO TESTING
The heads were tested on a 455 (now 468) engine mounted on a Super Flow SF-901 dynamometer. Jeff usually does not acknowledge the torque figure at the start of the pull because it could be incorrect. So the reading was taken at 3,900 to get a more realistic number on the 6X head pull. The correction factor for testing was 1.083.
BEST PULL: 6X HEADS WITH Q-JET
RPMCORRECTED TORQUECORRECTED HP
3,500524.5349.5
3,600514.4352.6
3,700518.4365.2
3,800521.3377.1
3,900522.0387.6
4,000521.2397.0
4,100517.2404.0
4,200502.2401.6
4,300495.9406.0
4,400504.7422.8
4,500509.0436.1
4,600506.0443.2
4,700497.6445.3
4,800494.3451.7
4,900486.4453.8
5,000471.4448.8
5,100457.7444.4
5,200455.8451.3
5,300451.2455.4
5,400439.2451.5
5,500427.1447.2
BEST PULL: KAUFFMAN ALUMINUNM HEADS WITH Q-JET
RPMCORRECTED CORRECTED
TORQUEHP
3,500547.2364.6
3,600549.5376.7
3,700548.1386.2
3,800548.4396.8
3,900548.6407.4
4,000548.3417.6
4,100546.3426.4
4,200545.9436.6
4,300543.4444.9
4,400539.4451.9
4,500537.4460.4
4,600534.9468.5
4,700532.5476.5
4,800523.5478.5
4,900518.9484.1
5,000511.4486.9
5,100501.6487.1
5,200492.7487.8
5,300485.4489.8
5,400478.1491.6
5,500471.9494.2
5,600463.6494.3

ABOUT THE DYNO ENGINE
Block: .060-over 455 = 468 ci
Crank: Stock nodular iron, 4.21 stroke, rotating assembly balanced
Rods: Crower forged steel, stock 6.625 length
Oiling System: Stock
Pistons: TRW forged, flat-top, exactly-zero deck
Compression Ratio: 9.95:1
Heads: 6X, 2.11/1.77 valves
Mods: Port-matched, cleaned up, bowl work, bigger exhaust valves
Valve Job: Custom, multi angles
Chamber Size: 91 ccs
Head Gasket: Fel-Pro 8518
Rocker Arms: Crane, 1.65:1 roller, Rhoads lifters
Cam: Crower PN 60919, hydraulic
Duration at .050: 231/240
Lift: .517/.517 with 1.65:1 rockers
Lobe Separation Angle: 113
Installed Position: Intake set at 109 centerline
Intake Manifold: OEM '68 cast iron
Mods: Reworked at carb flange to fit both bolt patterns, Q-jet and Holley
Carb: Q-jet, .073 primary jets, .048 custom-machined secondary rods
Carb: Holley, custom .093 primary jets, custom .097 secondary jets
Distributor: GM HEI, 20 mechanical advance
Timing: 30 total, all in by 2,500 rpm
Spark Plugs: AC R45TSX