Nick's Garage just dyno tested a 440 using factory HP exhaust manifolds, max wedge manifolds and headers.
Results:
HP manifolds---- 375 horsepower------ torque- 389
Max Wedge------ 410 HP ----------------- torque-446
Headers ---------- 419 HP ----------------- torque-463
The headers (1 7/8" tubes) increased 44 horsepower. Back in the day everybody claimed they only gave you 15 more horses.
All depends on the combination. Those dyno tests can be "rigged" by changing the camshaft. The results also will change a lot depending on the muffler and tailpipes that are used.
<---> this is where it is...... the correct cam and combo will help overcome the lack in exhaust efficiency . an effective cam would pick up the power on manifolds and there would be little if any from the addition of headers.......
