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.
The Dart Iron Eagle block...
The Dart Iron Eagle block (PN 31122221) has an optional 9.325-inch deck height. A stock Chevy small-block is 9.025 (as is the low-deck Iron Eagle), and the difference can be spotted by observing the distance from the water-pump hole to the deck surface. Another Iron Eagle feature is the camshaft centerline that's moved up and away from the crank centerline by 0.391 inch. Both these features allow longer strokes than would otherwise be practical.
The other feature for long...
The other feature for long strokes is the wider-than-stock crankcase, with each pan rail moved outboard 0.400 inch. To accommodate this change, the Iron Eagle (right) does not have a pad for a spin-on oil filter like the one on the driver side of the stock block (left), and the dipstick is relocated to the oil pan. Note the Iron Eagle's beefy steel splayed-four-bolt main caps; the rear cap accepts a stock-type wet-sump oil pump.
Jeff Jacobs at Dougan's Racing...
Jeff Jacobs at Dougan's Racing Engines pointed out that the Iron Eagle is intended for race applications with dry-sump oiling and therefore does not come with oil-drainback holes in the lifter valley. Since ours is a trail engine with drainback and cam-oiling needs, he drilled these holes, positioning them to ensure they did not intersect the bottoms of the lifter bores.