There are people that will tell you that the 455ci Oldsmobile Rocket motor makes a better street engine than a race motor. In truth, a stock 455 does have a couple of drawbacks that are detrimental to living life above 4,000 rpm for extended periods. The 455's Achilles' heel is a poor oil return system. The narrow passages from the stock heads do not allow oil in the valvetrain to return to the pan in an efficient manner. This condition can lead to instant death for a 455 that is run wide open for extended periods of time. As rpm increases, the oil goes to the top of the motor and stays there, draining the pan dry and starving the bottom end at the same time. It doesn't take long before the inevitable happens, and the dreaded screech of metal-to-metal contact bellows from the engine compartment, driving an Olds owner to tears. In the past, many people who have experienced a severe drop in oil pressure while running their Olds motor would immediately install a high-volume (HV) oil pump, which could worsen this condition. The fix that will allow your motor to survive extended high-rpm runs is to restrict the oiling system and install a larger-capacity oil pan.
Unfortunately, this lesson was learned after this Olds motor was rebuilt and put to use. Thankfully, Mondello Racing was contacted before any damage had occurred. After explaining to Lynn Welfriger at Mondello Performance Products that this 455 would live a high-rpm life (High for an Olds motor anyway!), he set us up with all the parts necessary to keep the motor from seizing. As soon as the UPS man dropped off the box of parts, we headed over to Maynard's Custom Cars and Trucks to have them work their engine building magic. Installation of the oil restriction system required the disassembly of the motor and sending the block to the machine shop to be cleaned. Since the motor had to come apart, we seized the opportunity to replace the nondescript, RV-grind camshaft with a new COMP Cams roller valvetrain. We also wanted to see how the motor would respond to having more fuel thrown at it. After dyno testing with the cam and ignition, a vintage Offenhauser tunnel-ram and a set of custom carburetor adapters were added to provide a home for a pair of 750-cfm Holley HP-series carbs, mounted sideways. All the performance gains were measured on Westech Performance Group's dyno in Mira Loma, California.
The oil restrictors let the motor rev freely to 5,500 rpm without fear of seizing. The increase in carburetion kept the motor happy on the top end and made a few extra ponies. Check out the accompanying photos and dyno numbers.
Dyno Results STOCK REBUILD
With an Edelbrock Performer manifold, a Demon 850-cfm carb, MSD ignition, and Hooker headers
RPM TORQUE HP
3,000 525 300
3,100 522 308
3,200 522 318
3,300 521 328
3,400 525 340
3,500 529 352
3,600 533 365
3,700 532 375
3,800 528 382
3,900 522 388
4,000 516 393
4,100 507 396
4,200 500 400
4,300 492 403
4,400 481 403
4,500 471 404
4,600 459 402
4,700 447 400
4,800 433 395
4,900 424 395
5,000 413 393
5,100 404 393
UPGRADED LEVEL 1- Same as the stock rebuild, but with COMP cam, rockers, springs, and pushrods
RPM TORQUE HP
3,000 490 280
3,100 490 290
3,200 494 301
3,300 496 312
3,400 507 328
3,500 527 351
3,600 531 364
3,700 536 377
3,800 538 389
3,900 538 400
4,000 536 408
4,100 526 411
4,200 520 416
4,300 513 420
4,400 507 425
4,500 501 429
4,600 494 433
4,700 485 434
4,800 474 433
4,900 465 434
5,000 456 434
5,100 449 436
5,200 442 438
5,300 435 438
5,400 422 434
UPGRADED LEVEL 2- Same as upgraded level 1, except for the Offenhauser Tunnel Ram, and dual Holley 750-cfm carbs
RPM TORQUE HP
3,000 512 292
3,100 514 304
3,200 518 316
3,300 520 327
3,400 526 341
3,500 535 356
3,600 538 369
3,700 541 381
3,800 537 389
3,900 531 394
4,000 526 401
4,100 518 404
4,200 510 408
4,300 505 413
4,400 498 418
4,500 493 423
4,600 488 427
4,700 481 430
4,800 473 432
4,900 464 433
5,000 456 436
5,100 455 442
5,200 450 445
5,300 447 452
5,400 440 452
