We learned that paying attention to air cleaner design and especially to how air enters the carburetor can pay huge horsepower benefits as power numbers continue to climb. The overall key appears to be ensuring sufficient space above the carburetor to allow air to enter the carb (or throttle-body) without creating turbulence that can cause power to suffer. It appears that maintaining roughly a 2- to 3-inch clearance above the top of the carburetor is a great way to offer your engine every opportunity to make power. This is not always possible with low hood levels and tight engine compartments. But the fact remains that should you choose to restrict the inlet air into your engine, then you can expect to lose power as a result of that compromise. It doesn't get any simpler than that.
Another way to look at this is with a simple question. How much money would you expect to pay to make an additional 14 hp?
Air cleaner assemblies or air filters don't make power, but the right combination of airflow-enhancing filter assemblies will help your engine make all the power it is capable of producing-and keeping that horsepower-devouring devil out of your details.
| Test 1 | Baseline with no air cleaner, 0-4779 750-cfm Holley w/choke |
| Test 2 | Flat base w/14x4-inch K&N filter and Flow Top |
| Test 3 | K&N Flow Control air cleaner w/14x4-inch filter |
| Test 4 | Flat base, 14x4-inch filter, Stub Stack, and Flow Top |
| Test 5 | 9-inch-diameter, 2-inch-tall air cleaner w/paper filter |
| | Test 1 | Test 2 | Test 3 | Test 4 | Test 5 |
| RPM | TQ | HP | TQ | HP | TQ | HP | TQ | HP | TQ | HP |
| 3,000 | 492 | 281 | 489 | 279 | 493 | 282 | 494 | 282 | 483 | 276 |
| 4,000 | 529 | 403 | 526 | 401 | 531 | 405 | 531 | 405 | 519 | 395 |
| 5,000 | 543 | 517 | 545 | 519 | 547 | 521 | 549 | 522 | 526 | 502 |
| 6,000 | 495 | 565 | 495 | 566 | 497 | 568 | 502 | 574 | 476 | 544 |
| Peaks | 545 | 567 | 545 | 572 | 552 | 575 | 551 | 581 | 528 | 546 |
Engine Specs* GM Performance Parts 454 H.O. short-block* 10:1 compression ratio* JE custom standard bore forged pistons* Crane mechanical flat-tappet cam, 252/262 degrees duration at 0.050, 0.554/0.554-inch lift, 110-degree lobe separation angle, Crane 1.7:1 Gold Race roller rockers* World Products iron Grumpy Jenkins Merlin heads, 2.300/1.88-inch valves, ARP headbolts, Crane dual valvesprings* World Products Merlin 4150 style single-plane manifold* Holley R4779-6 750-cfm mechanical secondary carb* Hooker 131/44-inch headers, 3-inch exhaust with Flowmaster mufflers* MSD billet distributor, MSD-7A CD ignition, MSD plug wires