Test 13: World Products S/R Torquer cylinder heads (PN 042660-2 67S) were installed (67cc chambers, 170cc intake runner volume, 2.02/1.60 valves). No other changes were made.Max 417 tq, 379 hpAvg 399 tq, 303 hp
Test 14-15: GMPP Vortec cylinder heads and COMP Cams 1.6:1 rockers (February 2003).
Since power fell off drastically in January's test, we knew we'd made some mistakes and had to redeem ourselves. To accomplish this we went back to The General and installed a new set of iron GMPP Vortec cylinder heads. We compared figures to the stock "camel hump" heads (Test 12) and found that even though the Vortecs actually dropped DM's compression by about 1/4-point to 9.25:1, that didn't stop them from adding more power. Then we swapped on our first set of 1.6:1-ratio rockers (previously only 1.5:1-ratio rockers would fit, due to pushrod interference) and were, once again, rewarded with more power.
Test 14: We installed iron GMPP Vortec heads (SDPC PN SD8060A, 64cc chambers, 170cc intake runner volume, 1.94/1.50 valves) with COMP Cams 1.5:1 Magnum roller-tip rockers (PN 1417-16) and an Edelbrock RPM "Air Gap" manifold (PN 7516).Max 435 tq, 409 hpAvg 413 tq, 330 hp
Test 15: COMP Cams 1.6:1 Magnum roller-tip rockers (PN 1418-16) were installed.Max 440 tq, 416 hpAvg 417 tq, 333 hp