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Solid Roller Cam and Single Plane Intake Manifold Upgrade for a 427 Big-Block - L89 Version 2.1

We Pump Up The Power Of Our 427 With The Addition Of A Solid Roller Bumpstick And Single-Plane Intake.

By , Photography by

Back in our January issue, we built our own version of the L89 big-block 427 using all aftermarket components. Our rev-happy Rat combo used a Dart Big M block, Dart 275cc Pro 1 heads, Eagle crank and rods, JE pistons, Weiand dual-plane intake, Holley 750 HP carb, and a Comp valvetrain, including a Big Mutha Thumpr cam. The recipe ended up producing 507 hp at 6,000 rpm and 471 lb-ft at 4,100 rpm.

Being the power junkies that we are, the engine wasn't even cooled down before we asked Jeff Strech (Speed-O-Motive's engine guru) "What can we do to make more?" Without hesitation he said, "Your combo is not using the heads to their full potential. We can swap in a bigger cam and a single-plane intake to wake that sucker right up."

While the Big Mutha Thumpr cam sounded very aggressive at idle, the 0.522/0.507 (intake/exhaust) lift was not using all the air flow capabilities the Pro 1 heads provided, just like Jeff had said. The heads flow (per Dart's flow sheet) 352cfm intake and 258cfm exhaust at 0.700-inches of lift at 28 inches of water.

Not needing any more convincing than that, we sat down with Jeff and picked his brain for a cam and intake selection. Jeff said, "The intake is easy-just pick up Dart's single-plane. For the cam, let's go with a custom grind I've had excellent results with." We let him know this better not be some secret grind because we were going to publish the specs.

He was cool with that so we grabbed the Comp Cams catalog and flipped to the BBC solid roller section. Jeff told us to have a solid roller ground with Hi-Tech 0.420 lobes, lobe number 4017 on the intake and lobe number 4024 on the exhaust, that have 0.715 lift specs, a 108 degree lobe separation, and a 4/7 firing order swap.

We will get into specifics of all this in the photo captions. We also picked up a Cloyes timing chain cover from Summit Racing with an integrated cam button to simplify setting the cam endplay. Plus, the stock stamped cover was too flimsy to keep this cam under control anyway.

We did all the work and dyno testing over at Speed-O-Motive in Covina, California, with Jeff doing most of the grunt work. We also have video of the engine making a pull so be sure to check out www.superchevy.com so you can hear it for yourself.

BEFORE
RPM POWER TORQUE
3,500 302 453
3,600 316 461
3,700 328 466
3,800 338 467
3,900 348 469
4,000 357 469
4,100 367 471
4,200 374 468
4,300 379 463
4,400 386 461
4,500 393 459
4,600 401 458
4,700 410 458
4,800 420 460
4,900 430 461
5,000 440 462
5,100 452 466
5,200 464 469
5,300 472 467
5,400 480 467
5,500 484 462
5,600 490 459
5,700 495 456
5,800 500 453
5,900 504 449
6,000 507 444

RPM POWER TORQUE
3,500 302 453
3,600 318 464
3,700 332 472
3,800 345 477
3,900 356 479
4,000 364 479
4,100 371 476
4,200 376 471
4,300 379 463
4,400 382 457
4,500 388 453
4,600 396 452
4,700 405 452
4,800 413 452
4,900 423 454
5,000 437 459
5,100 453 467
5,200 471 476
5,300 490 486
5,400 508 494
5,500 522 498
5,600 533 500
5,700 540 498
5,800 547 495
5,900 553 492
6,000 557 488

RPM POWER TORQUE
3,500 305 457
3,600 321 468
3,700 335 475
3,800 347 479
3,900 358 482
4,000 367 482
4,100 374 479
4,200 379 473
4,300 381 466
4,400 384 458
4,500 389 455
4,600 398 455
4,700 408 456
4,800 417 456
4,900 428 458
5,000 442 465
5,100 460 474
5,200 478 483
5,300 497 492
5,400 513 499
5,500 527 503
5,600 539 505
5,700 547 504
5,800 552 500
5,900 557 496
6,000 561 491
6,100 566 487
6,200 570 483
6,300 572 477
6,400 574 470
6,500 575 464

SOURCES
Trans-Dapt Performance Products
12438 Putnam Street
Whittier
CA  90602
562-921-0404
www.tdperformance.com
Comp Cams
3406 Democrat Road
Memphis
TN  38118
800-999-0853
www.compcams.com
Summit Racing Equipment
PO Box 909
Akron
OH  44398
800-230-3030
330-630-0240
www.summitracing.com
Dart Machinery
353 Oliver Street
Troy
MI  48084
248-362-1188
http://www.dartheads.com
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