The goal was high-velocity street-type heads for 2,000- to 6,000-rpm use. In the small-block, 230cc ports at 5.2 inches length (BBCs are 6 inches) and a Super Victor manifold proved to be just the right size for a 454 running in the midrange rpm zone. After flowing the heads (318 cfm at 0.600), I selected a 2.10-inch intake valve and a custom cam with 230/242-degree duration, 0.640-inch lift, and a 112-degree lobe-separation angle.
When it came to exhaust, I wanted to use custom headers and a side-mounted system-all while keeping the noise level acceptable. That isn't easy to accomplish when you have about 600 hp on tap. I knew that I'd have to use the largest Walker Super Turbo mufflers they make, 'cause they have a flow-through design and lots of packing.
In order to use these mufflers, I had to dump the spare tire and under-tank rack, and run an under-body dual system with a custom x-crossover. Then, to get the sidepipes working, I had my welder put in two Quick Time Performance electric cut-out valves. I have a lever switch on the center console that allows me to open the exhaust at any time, even secretly while the engine is off. This works great for surprising folks.
Here's the method I use for exhaust tuning:
1. Apply Alexander Graham Bell's formula for primary-pipe length according to the exhaust valve's opening point.
2. Use his second formula for the primary-pipe diameter.
3. Choose a tri-Y configuration for a broader tuning range of 3,000 rpm on the street.
4. Use ideal mergers to control turbulence.
5. Keep the collector diameter narrow and employ a merge collector to maintain velocity and further minimize turbulence.
6. Apply a heat-retention ceramic coating to keep the temperature up.
7. Use bullet catalytic converters to add just a bit of backpressure and keep the car smelling clean. Without them, too much scavenging at low rpm is likely.
8. Follow that with neck-downs to the exhaust piping and low-restriction mufflers (MagnaFlow, Borla, or DynoMax Super Turbo). Be aware that a 2.5-inch system with mandrel bends will support 500 hp. Sharkee's 600hp system uses 3-inch pipe all the way.
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