The Heads Stock Iron We used the stock iron castings as the baseline cylinder head for comparison purposes. This is the 168cc intake port head that comes on the Goodwrench crate engine and is representative of a typical 1.94/1.50-inch valve head with 76cc chambers. The flow numbers indicated the intake port wasn’t able to reach even the 200-cfm mark and that the exhaust was also unremarkable. The baseline power numbers are also down due to reduced compression (8.5:1 vs. 9.6:1) compared with the other heads; this was the only head tested with a 76cc combustion chamber, while the rest benefited from 64cc chambers. This represents a difference of more than one point of compression or between 3 to 4 percent power. We also weren’t able to run a 1.6:1 roller rocker with these heads because of retainer-to-seal interference problems. We didn’t have time to machine the heads, so we went with 1.5:1 rockers. Stock Iron, Casting #462624 Peak HP 358 at 5,800 Peak TQ 379 at 4,300 Valve Sizes 1.94/1.50 Intake Port 168cc Chamber 76cc Valvesprings 1.250 single w/ damper Iron Vortec The production-based iron Vortec head represents one of the best budget investments for power for the small-block Chevy. These heads were only used on a few models of Vortec truck engines, but their longevity is ensured because they flow so well. The main limitation with these heads in pure stock form is their inability to utilize valve lift above 0.450 inch. In stock form, the retainers hit the seals with valve lifts above this 0.450-inch figure. We anticipated this issue and used a set of Scoggin-Dickey–modified Vortec heads with the valve guides machined for additional clearance and fitted with better, Z28-style valvesprings. This added roughly another $160 to the price of the heads but allowed us to use 1.6:1 roller rockers to level the playing field against the other heads in the test. In addition, you must use guided rocker arms and center-bolt valve covers, and the intake manifold bolt pattern is unique, requiring a specific intake manifold. If you are considering Vortec heads, keep in mind that swapping them in will require these parts at additional cost. On the plus side, the Vortec intake port flows 42 cfm better than the stock heads at 0.500-inch lift and 18 cfm better on the exhaust side. Vortec Iron, Scoggin-Dickey Modified PN SD8060A2, $779.90 Peak HP 378 at 5,300 Peak TQ 408 at 4,300 Valve Sizes 1.94/1.50 Intake Port 170 Chamber 64 Valvesprings 1.250-inch single spring w/ damper Dart SHP With 200cc intake ports, the Dart head is the largest of the budget heads we tested. As you can see from the horsepower and torque numbers, these heads finished in a virtual tie with the Patriot heads in terms of peak power. The flow numbers indicate even more potential with these heads, since the flow numbers peak at 0.600-inch lift and our cam barely cleared the 0.500-inch-lift threshold. So with a hydraulic roller cam that could generate closer to that 0.600-inch-lift peak flow number, you can expect these heads to make a lot more power. And unlike most of the other heads in this test, these came with larger, 1.43-inch-diameter springs that are intended for use with a hydraulic roller camshaft. Dart SHP 200 PN 127322, $931.98 Peak HP 419 at 6,200 Peak TQ 417 at 4,200 Valve Sizes 2.02/1.60 Intake Port 200cc Chamber 64cc Valvesprings 1.437-inch, dual springs Jegs We were pleasantly surprised with how well the Jegs heads worked. Finishing Third in peak horsepower, First in peak torque, and Third in average power, the Jegs head is certainly a dark-horse candidate for best overall performer, especially when you consider its strong showing in torque and the small difference in average power among the top three heads in that category. Plus, the Jegs head also rounded out a great, three-way, mail-order-catalog shootout between Jegs, Speedway Motors, and Summit Racing. Jeg’s 180cc PN 5140000, $959.98 Peak HP 408 at 5,900 Peak TQ 421 at 4,300 Valve Sizes 2.02/1.60 Intake Port 180cc Chamber 64cc Valvesprings 1.250-inch single spring Article Attachments Budget Cylinder Head Flow Data.pdf « | 1 | 2 | 3 | 4 | » | View Full Article By Jeff Smith Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!