Flow Report
The following tests were performed on Jim Grubbs Motorsports' computerized SuperFlow 600 flowbench accompanied with Performance Trends' Port Analyzer program that averages 15 data samples per valve lift.
Test 1 was the stock 460 heads that originally came on our 460ci Ford mule motor from last month with its existing valve job and OE valves. Test 2 was with the same valves with a three-angle valve job. Test 3 employed a 32-degree back-cut on both the stock intake and exhaust valves. Test 4 used a larger 1.76-inch Cobra Jet valve with a ported exhaust port. Test 5 used a 32-degree back-cut Manley 1.71-inch valve with the port throat opened to 88 percent of the valve diameter and with a radiused chamber wall to reduce valve shrouding. The chamber side of the valve seat was also radiused to improve low-lift flow along with a slight radius on the chamber side of the exhaust valve.
Edelbrock flow numbers were generated from an out-of-the-box aluminum Performer RPM 460CJ on a different SuperFlow bench than the stock heads were flowed. In addition, the Edelbrock heads were flowed with an exhaust pipe attached, while the iron heads did not have the pipe, which would reduce their flow numbers slightly at valve lifts above 0.100 inch. As you can see, the Edelbrock heads offer substantially better exhaust-port flow numbers compared to our best ported iron head version. This would result in much better power at or near peak horsepower. Also note how the Edelbrock heads offer a clearly superior average E/I percentage of 70 versus our ported iron heads at 57.9 percent.
All flow numbers for this story were generated on a SuperFlow 600 flow bench and are in cfm. All test were performed at 28 inches of water test depression. | |
Intake Flow Test Test Test Lift 1 2 3 Diff.
Edelbrock0.100 66 67 68 1 680.200 125 93
142 17 1360.300 185 185 204 19 2010.400
225 225 241 16 2530.500 253 253 261 8
3000.600 271 271 271 0 305Exhaust Flow Test
Test Test Test Test Lift 1 2 3 4 5
Diff. Edelbrock0.100 47 52 54 51 60 13 610
.200 89 93 97 96 105 16 1090.300 117
119 122 124 127 10 1480.400 127 133 134
137 134 7 1740.500 129 135 135 138 132
3 1910.600 129 135 135 137 130 1 202A
vg. E/I% 59.8 61.2 57.0 57.5 57.9 70.0