1 ½-Inch Flowtech Intermediate-Length Headers
Rather than begin at the bottom and put cast-iron exhaust manifolds on the 383ci for comparison, we figured that anyone with a 440hp stroker wouldn't insult the engine with such restriction. We bolted 1 ½-inch Flowtech headers on the Edelbrock heads. Matching gaskets are part of the Flowtech kit, but we used Fel-Pro pieces because of their reputation for durability and seal efficiency. We were surprised to see that the horsepower was down from the advertised peak number by only 11 hp, and the grunt curve showed in excess of 21 lb-ft of additional peak torque above the advertised number. It appeared that the small-diameter tubing provided some impressive low-end and midrange torque numbers, while the intermediate-length design promoted as much upper-end power as possible to create an outstanding street/strip power curve.
RPM; TQ; HP
3,000; 429; 245
3,100; 434; 256
3,200; 438; 267
3,300; 442; 278
3,400; 445; 288
3,500; 449; 299
3,600; 452; 310
3,700; 455; 321
3,800; 457; 331
3,900; 459; 341
4,000; 460; 350
4,100; 461; 360
4,200; 459; 367
4,300; 459; 376
4,400; 456; 382
4,500; 455; 390
4,600; 454; 398
4,700; 452; 405
4,800; 451; 412
4,900; 447; 417
5,000; 441; 420
5,100; 436; 424
5,200; 430; 426
5,300; 425; 429
5,400; 420; 432
5,500; 414; 434
5,600; 408; 435
5,700; 401; 435
5,800; 391; 432
5,900; 382; 429
6,000; 374; 428
Average; 437; 371