Pure Grunt

Everyone talks torque, but do they really mean it? After all, small-block Chevys are the omnipresent four-wheeling powerplants, but small-blocks are unlikely cohorts with huge torque numbers. Even if you build a 383 stroker that visits the neighborhood of 500 lb-ft, it probably has a choppy cam with no low-end driveability and clouds of pig-rich, 91-octane exhaust fumes. But what if you could have big-block cubes in a small-block package?

You can. Using a Dart Iron Eagle block with a raised cam and deck height (make sure to read the sidebar), we built a 450ci small-block by combining a 4.165-inch bore with a 4.125-inch stroke. A normal 350ci Chevy is 4.00x3.48, and a 383 stroker is 4.03x3.75. Our big-inch, 9.3:1-compression small-block runs on 87-octane dog water (perfect for those Baja trips) and grunts out over 500 lb-ft from 2,000 clear through 5,000 rpm, peaking at a stout 571 lb-ft at a low 3,700 rpm.

It's only incidental that it also spits up 480 hp at a mere 4,900 rpm. If you can't frag your transfer case with this thing, something's wrong with you.But also know this: When you see a magazine pat itself on the back for big numbers on the dyno, those numbers are generated at wide-open throttle. That's only relevant to a mud-bogger, a dune-flogger, or to a total hack of a rockcrawler. For a rock-hound with finesse, it's more important to consider lug-ability (how low will it pull?) and part-throttle control, both of which are compromised by small cubes and big cams.

That's why our 450-incher benefits from a miniature Comp Cams hydraulic roller for an idle of 600-700 rpm with no lope whatsoever and a vacuum reading of 16 to 17 inches. That'll be happy with any power-brake system, run smoothly with an EFI setup, and pull as low as 300 rpm under load. And, since many of you will still want more, we also tried a bigger cam for 530-plus hp at 5,200 rpm, and then we gave a shot with a blower for you show-truck guys. How's 700 lb-ft and 720 hp grab you? Read on.

Iron Eagle: Secret to Big Cubes
The idea of a big-inch small-block first hit us about 10 years ago when GM introduced the Rocket Block, an Olds-branded casting designed specifically for long strokes by incorporating a raised camshaft location and 0.800-inch-wider-than-stock oil-pan rails. The Rocket was also available with a deck height (crank centerline to deck surface) of 9.325 inches, 0.300 taller than the blueprint spec of a stock Chevy block. The taller deck height allowed for longer connecting rods and/or a taller piston compression height than would otherwise be practical with a very long stroke.

When the Rocket Block was new, its special features demanded a bunch of fabricated parts that made the engine impractical for a backyard wrench to assemble or afford. Then GM discontinued the Rocket. Today, Dart offers the Iron Eagle small-block casting with all the benefits of the Rocket block, and several aftermarket companies have the parts needed to easily slam together a big-inch small-block.

If you're considering the price of an engine built with a stock block and China-made budget crank and rods, then the Dart 450-incher will be way more expensive. But if you compare the prices of the custom Iron Eagle parts with conventional-style components of the same top quality that we used in this buildup, then going big will run you about an extra $500. Here's the list of all the special parts you'll need for an Iron Eagle block compared to a standard block, plus the part numbers of the specific components we used.

*Spread-rail oil pan (Moroso PN 20193)
*Raised-cam timing set (Comp Hi-Tech PN 3146KT)
*Longer, big-block-style oil-pump driveshaft (ARP 135-7901)
*Big-block-style fuel-pump pushrod (ARP 135-8701)
*Intake-manifold spacers (Dart PN 622100002)
*Remote oil filter (Moroso Omni Filter PN 22285)
*Slip-collar-style distributor (MSD PN 85561)
*Line-bored-400-Chevy-style rear main seal (Fel-Pro 2909)
*2.375-inch, Ford FE-style rear cam plug

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.