Pure Grunt

The Dyno Flog
We tested the 450ci small-block in three different configurations: tiny cam, medium cam, and blown. There's a power curve here to satisfy any four-wheeling need.The first setup used a Comp Cams XE270HR hydraulic roller 'stick with 218/224 degrees of duration at 0.050 tappet lift, a 110-degree lobe separation, and lift of 0.528/0.535 inch. That's pretty tiny, but with the 9.3:1 compression and aluminum heads it'll never ping on 87 octane, though we did crank the timing to a total advance of 38 degrees.

That's a bit high, indicative of the reduced efficiency of the low compression. This would be a safe 91-octane engine with another point of compression, and would make roughly 4 percent more power at 10.25:1. But even on 87 octane, it made a peak of 480 hp from 4,900 through 5,400 rpm and a torque peak of 571 lb-ft at 3,700 rpm. More significantly, the small-block never made less than 500 lb-ft from a very low 2,000 rpm clear through 5,000 rpm.

Next, we added a Comp Cams XE294HR hydraulic roller grind with 242/248 degrees at 0.050, a 110 LDA, and 0.571/0.599 lift with 1.6:1 rockers. A bit big for 9.3:1 compression, but it idled at 800-900 rpm with 12 inches of vacuum. The affect on the power curve is the textbook-perfect example of what happens with a bigger cam. The shapes of the curves for the XE270 cam and the XE294 cam are very similar, but they pivot away from each other at 3,750 rpm.

Finally, for you show-truck guys, we couldn't resist trying a supercharger. The 420ci Holley MegaBlower that we tested was recently discontinued, but Weiand still offers both 6-71 and 8-71 GMC-type lungs that will match the power--which was 700 lb-ft forever and 722 hp at 6,200 rpm. It probably makes 600 lb-ft right off idle. The carbs were two Holley HP, 750-cfm blower carbs (PN 0-80576) that were jetted perfectly right out of the box, plus we dialed the timing back to 30 degrees total. On 76 Products 91-octane pump gas, there was no hint of detonation with the blower 9 percent underdriven for 5 pounds of boost at peak torque (4,100 rpm) and a bit over 7 psi at peak horsepower (6,200).

Dyno Results

Predictably, the small cam makes more horsepower and torque below 3,750, and the bigger cam makes more power after that point. The longer duration of the bigger cam moves up the rpm at peak torque by a few hundred rpm. Since horsepower is a function of torque and rpm, and since the distance between the torque and the power peaks is about 1,500-1,800 rpm, the engine will make more torque at higher rpm and therefore make more peak horsepower. Specifically, the larger cam made 582 lb-ft at 4,100 rpm and 536 hp at 5,700. Interestingly, the actual peak torque value only changed a little bit, but the horsepower jumped by 56 points. On the downside, the big cam gives up as much as 40 lb-ft at points below 3,000 rpm.