Edelbrock claims their heads will work with up to .600 lift camshafts, and we found that to be true. This combination utilizes 1.6 ratio rocker with the .590 lift cam for a net valve lift of .629; we knew we were exceeding the advertised limits of springs, but by checking the open and seat pressures of the springs we determined they were compatible with our camshaft. We also checked for coil-bind and keeper-to-guide clearance at maximum lift, and discovered we had plenty of room to spare before either would be an issue. Since the springs passed the test, we checked piston-to-valve and piston-to-head clearances and found them to be adequate as well. The only issue we encountered was that Edelbrock relocated the spark plug toward the exhaust valve in their heads and slightly away from the stock location. While the relocated plug does promote more efficient combustion, it also places the spark plugs out of the plug reliefs cut in our piston domes. The solution to this problem was to either index the plugs or allow them to be smashed by the pistons; we chose to index the plugs.
A nice feature of the Edelbrock heads is they utilize stock hardware, so our stock length head studs, as well as manifold hardware and rocker arm assemblies, could be reused. The only items that were not interchangeable were the spark plugs, so we installed a set of Champion C59CX plugs. Another great feature is the exhaust mounting bolt holes don't invade the water jackets, so no more sealant mess or coolant seeping from around the header bolts, a definite advantage. A comparison of the 452 casting to the Edelbrock revealed that the out-of-the-box port size was very similar to our ported 452s, so we didn't expect much gain by flow alone. We did notice a difference in the combustion-chamber design with Edelbrock's heads having a somewhat closed-chamber design offering more quench than the openchamber steel heads. The combustion-chamber design, along with the relocated plug, should offer a power increase over the 452s, but how much? Read on and find out.
With our checking complete, we installed the heads with new gaskets and torqued our head studs to 70 lb-ft. After setting valve lash and reinstalling our intake and headers, we were ready to warm up the engine and make another pull on the dyno. So that the results of the test were accurate, we left everything else the same as our baseline pull with the steel heads. We re-installed the Torker intake and the 1050 Dominator, and left the carb jetting, timing, and valve lash unchanged for a valid comparison. The following results speak for themselves. we not only saw a power increase, but also a broadening of the torque and horsepower curve. We also found the Edelbrock heads responded well to a change in intake manifolds, further optimizing our combination. Check out the dyno results, and we're sure you'll agree that Edelbrock's heads are definitely a worthwhile investment.