Headers
As with so many of the bolt-on components we've discussed here, headers are an excellent way to improve performance-when properly matched to an engine. Larger tubes may mean more power, but not if gas velocity drops. Case in point: the "Header Ho-Down" in our April '04 issue. We tested a Smeding Performance 383 crate motor (rated at 440 hp and 440 lb-ft), fitting four different headers ranging from 1 1/2-inch FlowTech shorties to 1 7/8-inch Hooker long-tube pipes. As you can see, horsepower increased, but torque began to fall off with larger primaries-especially in the midrange. Choose carefully. Prices range from $250 for the FlowTechs to just less than $600 for ceramic-coated Hooker long-tubes.
1 1/2-inch
435 hp at 5,600 rpm
461 lb-ft at 4,100 | 1 5/8-inch
441 hp at 5,400 rpm
468 lb-ft at 4,400 |
1 3/4-inch
449 hp at 5,600 rpm
467 lb-ft at 4,500 rpm | 1 7/8-inch
451 hp at 5,700
459 lb-ft at 4,400 |
Throttle Body
Bigger could be better for fuel-injected motors, too. On the other hand, bolting on a new throttle body isn't just about increased airflow. It's also about smoother increased airflow, creating more power and better throttle response. TPI Specialties has a couple of LT1-compatible goodies. The 52mm unit (900 cfm) is a rebuilt factory casting that has been rebushed, bored out from 48mm to 52mm, and fitted with a TPIS air foil. We're told you can plan on 15-plus extra horsepower on a stock motor. Then there's TPIS 58mm billet throttle body (1,100 cfm), which features ball bearings on the shaft and a built-in air foil. While it can be used on a stock motor, it's also well suited to big-inch applications. Then there's the new 90mm throttle body for the LS6 manifold-that's right, an LS2-sized butterfly, adapted to fit the Gen III motor. Look for another 8 hp from an almost-stock LS1. The 52mm piece comes in at just under $300; the big boy goes for $500, and the new 90mm unit for $499 (with exchange).