The song remains the same-horsepower has never been easier to make than it is today. For you normally aspirated fans, Ken Duttweiler slipped this small-block 347ci stroker motor beauty up on the dyno, and as soon as it hit 514 hp at 6,800 rpm, we were definitely interested.
To begin with, Duttweiler started with a basic Scat rotator package that offers a 4340 forged steel 3.40-inch stroke crank with I- or H-beam rods, and a set of flat-top SRP forged pistons with 11/416-inch ring packages that creates an incredibly strong bottom end. Duttweiler needed this to be durable because he planned on spinning this little stroker with a serious cam and head package.
Power is all about matching components. Duttweiler wanted to see what the new Trick Flow Specialties R-series Twisted Wedge heads would do on a medium-displacement Ford small-block, and this seemed like a perfect opportunity to test them out. The heads are the race version of the street Twisted Wedge Ford heads, complete with 206cc intake ports and a serious 0.500-inch raised exhaust port to overcome the 302's tendency to pinch the exhaust ports down to nothing.
The 2.08/1.60-inch valves are canted to unshroud the valves as they increase in valve lift and, combined with the 61cc chamber, create an optimal combustion situation. We didn't have time to flow-test these particular heads, but TFS's own flow sheets make these heads out to be winners, especially looking at the 0.300- and 0.400-inch valve lift flow numbers.
Contemporary engine theory places a great deal of emphasis on mid-lift flow numbers. The Comp mechanical roller cam that Duttweiler spec'd maxes the valve lift at slightly over 0.635 inch. But the theory states that emphasizing flow potential at around 65 to 75 percent of maximum valve lift (in this case roughly 0.410- to 0.475-inch valve lift) will generally improve the overall power curve, not just the top-end power. TFS's flow numbers are outstanding for this cross-sectional-size port with a 0.400-inch valve lift flow number of 242 cfm!
Duttweiler went with a recommendation from Comp on the camshaft and hit the 500hp mark with a custom spec grind that anyone can order by just giving them the specs in our cam spec box. This is certainly no slouch cam, and the idle vacuum numbers reinforce that with barely 8 inches of manifold vacuum at 950 rpm. That's another reason we didn't pull the engine down below 3,600 rpm since the torque wasn't anything to write home about below that level. That means you'd need at least a 3,000-rpm stall speed converter if you're running an automatic, or preferably a manual trans with a deep First gear.
The Victor Jr. intake was a natural choice to complement the head and cam selection, and Duttweiler also chose a 131/44-inch header package from Hooker to balance out the exhaust side. We ran this test through a 211/42-inch set of exhaust pipes leading to a pair of Borla Pro X/S stainless steel mufflers. To keep things simple on the water pump side, we also added a CSI electric pump to keep the engine cool.
Testing Car Craft's dyno guy Ed Taylor cranked the small-block up on the dyno, and after some simple tuning exercises to get the timing at 34 degrees and the jetting in the ballpark, it was time to make some noise. These dyno tests were truly fun because this small-block just loved to run. Peak torque on all the tests hovered right around 5,200 rpm, starting out at 449 lb-ft of torque; that's just shy of 1.3 lb-ft per ci, which is a great number. Peak horsepower swung in at a high 6,800 rpm, but this Ford also pegged the needle at 511 hp! Yeehaw.
Next up, Taylor added a Wilson Manifolds tapered four-hole spacer that raised the entire power curve and added as much as 8 hp at a couple of points along the way. Not bad for a simple bolt-on piece. It appears this spacer may have improved the mixture distribution in the manifold, or at least contributed to enhancing mixture homogeneity throughout the entire rpm curve.
The great news here is that we now had a 347ci small-block making 514 hp with a 1,600-rpm power band separating peak torque and peak hp. Cranking up our steam-powered calculator, that comes out to an amazing 1.48 hp per ci. Baby, that will spank more than its share of street pretenders!
Finally, for Test 3, Taylor added a Holley HP 830-cfm carb to see if the stroker Ford would respond to slowing the incoming air a little. Peak power improved slightly, but at a loss through most of the rest of the curve. Here's a case where a bigger carb isn't better, even with the peak hp improvement.
If we cut to the chase, this is a stout small-block that can be assembled with virtually all off-the-shelf parts. Sure, the cam is a special order, but it still uses a stock distributor gear. If you like the idea of 500-plus horsepower, a rough idle, and lots of gear, then this is a horse that's ready to ride.
Cam Specs Cam Description Adv. Duration @ Valve Lobe Dur. 0.050 Lift Sep. Mech. Roller, 286R Int. 276 246 0.635 110 Exh. 284 254 0.635 These specs are with a 1.6:1 rocker ratio Lash: Int., 0.012-inch; Exh., 0.014-inchPower TestsTest 1 was our baseline run with a 750-cfm Holley HP carb on 91-octane pump gas with 10.5:1 compression
Test 2 added the Wilson Manifolds 1-inch tapered spacer. Note the overall increase in torque.
Test 3 added an 830-cfm Holley carb along with the 1-inch spacer. Note that the larger carburetor made more peak power, but also cost torque throughout all but the peak power area.
TEST 1 TEST 2 TEST 3 RPM TQ HP TQ HP TQ HP 3,{{{600}}} 426 292 427 292 416 285 3,800 426 308 429 311 422 305 4,000 424 {{{323}}} 426 324 421 320 4,{{{200}}} 423 338 427 341 422 337 4,400 425 356 431 361 425 356 4,600 429 376 440 385 434 380 4,800 440 402 446 408 444 406 5,000 447 425 454 433 450 428 5,200 449 445 457 453 454 450 5,400 448 461 451 463 451 464 5,600 442 471 444 473 444 473 5,800 435 480 442 487 440 485 6,000 428 488 432 494 435 497 6,200 414 489 418 493 422 498 6,400 408 497 410 499 414 504 6,600 403 506 408 513 408 513 6,800 394 511 397 514 398 515 Parts List Component Manufacturer Part Number Production block OEM used Stroker crank kit Scat 1-347FHPS Cam, mech. roller Comp Cams custom order Heads, assembled Trick Flow TFS-52400100 Intake, Victor Jr. Edelbrock 2921 Carburetor, 750 HP Holley 0-80529-1 Carburetor, 830 HP Holley 0-80509-1 Carb spacer, four-hole Wilson 024110 Oil pan, {{{Fox}}} chassis Moroso 20509 Oil pump pickup Moroso 24517 Headers, 131/44-inch Hooker see catalog Distributor, billet MSD 8579 6AL box MSD 6420 Plug wires, universal MSD 3118