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Aftermarket Heads - Head to Head
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| Ported GM Bow Tie AFR 180 CNC | | Lift (Inches) | Intake Flow (cfm) | Exhaust Flow (cfm) | Intake Flow (cfm) | Exhaust Flow (cfm) | | 0.200 | 116 | 107 | 140 | 112 | | 0.300 | 169 | 143 | 201 | 152 | | 0.400 | 212 | 166 | 244 | 190 | | 0.500 | 239 | 169 | 260 | 208 | | 0.550 | 225 | 172 | 262 | 214 | | 0.600 | 228 | 174 | 263 | 219 | | Head Gasket Thickness vs. Compression Ratio | | Although bore size affects compression ratio, Fel-Pro reports that a general formula for calculating how head gasket thickness affects compression ratio is as follows. For every 0.005-inch thickness increase/decrease, gasket volume changes by about 1 cc, which translates to slightly less than 1/8 (0.125) of a point of compression ratio. We did the exact math on our 327 V-8 and came up with these figures: | | | | Gasket Thickness | Compression | Notes | | (inches) | Ratio | | | 0.015 | 10.68:1 | Steel shim previously on 327 | | 0.020 | 10.61:1 | | | 0.030 | 10.31:1 | | | 0.040 | 10.03:1 | Fel-Pro gasket used on this test | | 0.050 | 9.76:1 | | | | Dyno Test | | | | | Bow Tie | | AFR 180 CNC | | | RPM | HP | Torque | HP | Torque | | 3,000 | 194.5 | 340.4 | 194.6 | 329.5 | | 3,100 | 198.8 | 336.9 | 194.9 | 329.8 | | 3,200 | 205.3 | 336.9 | 201.0 | 329.9 | | 3,300 | 214.1 | 340.8 | 209.7 | 333.7 | | 3,400 | 223.1 | 344.6 | 217.7 | 336.3 | | 3,500 | 230.5 | 345.9 | 225.0 | 337.6 | | 3,600 | 236.3 | 344.7 | 230.6 | 336.4 | | 3,700 | 242.0 | 343.5 | 237.0 | 336.5 | | 3,800 | 246.8 | 341.1 | 244.4 | 337.8 | | 3,900 | 252.5 | 340.0 | 251.8 | 339.2 | | 4,000 | 260.9 | 342.6 | 260.3 | 341.8 | | 4,100 | 270.4 | 346.4 | 270.8 | 346.9 | | 4,200 | 280.0 | 350.1 | 282.5 | 353.2 | | 4,300 | 288.8 | 352.7 | 293.4 | 358.3 | | 4,400 | 296.6 | 354.1 | 303.4 | 362.2 | | 4,500 | 304.5 | 355.4 | 312.5 | 364.8 | | 4,600 | 312.5 | 356.7 | 321.7 | 367.2 | | 4,700 | 320.4 | 358.1 | 331.0 | 369.8 | | 4,800 | 328.5 | 359.4 | 340.5 | 372.6 | | 4,900 | 335.4 | 359.5 | 348.8 | 373.9 | | 5,000 | 341.1 | 358.3 | 356.0 | 374.0 | | 5,100 | 345.6 | 355.9 | 363.2 | 374.1 | | 5,200 | 350.0 | 353.5 | 369.1 | 372.8 | | 5,300 | 355.6 | 352.3 | 375.0 | 371.6 | | 5,400 | 361.1 | 351.2 | 382.2 | 371.7 | | 5,500 | 367.8 | 351.3 | 389.3 | 371.8 | | 5,600 | 373.3 | 350.1 | 396.5 | 371.9 | | 5,700 | 377.3 | 347.7 | 402.3 | 370.7 | | 5,800 | 381.3 | 345.3 | 406.7 | 368.3 | | 5,900 | 383.8 | 341.6 | 412.4 | 367.1 | | 6,000 | 387.5 | 339.2 | 416.7 | 364.7 | | 6,100 | 392.6 | 338.0 | 420.8 | 362.3 | | 6,200 | 397.6 | 336.8 | 424.9 | 359.9 | | 6,300 | 399.8 | 333.3 | 430.3 | 358.8 | | 6,400 | 401.7 | 329.6 | 435.8 | 357.6 | | 6,500 | 401.9 | 324.8 | 439.6 | 355.2 | | 6,600 | 400.3 | 318.5 | 442.0 | 351.7 | | 6,700 | 394.2 | 313.6 | 442.5 | 346.8 | | 6,800 | 385.6 | 308.1 | 442.8 | 342.0 | | 6,900 | 380.8 | 304.4 | 439.6 | 334.6 | | 7,000 | 374.4 | 300.1 | 438.9 | 333.3 |
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Air Flow Research
10490 Ilex Avenue, Dept. MMFF
Pacoima
CA
91331
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Westech Performance Group
11098 Venture Dr., Unit C
Mira Loma
CA
91752
9-09/-685-4767
www.westechperformance.com
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COMP Cams
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