Quote:
Originally Posted by jhautz
Man this thread brings me back. lol
back in my day we would put in bypass valves in the exaust right after the header. It was basically a pipe with a y on it. the header flowed into the main end, and one side of the Y went into the normal exaust system, and the other ran to short straight pipes that basically just lead to the front wheel well to get the exaust out from under the hood. When you wanted power you pulled the cable operated lever inside the car and the flaps opened up the straight pipes and the thing roared with no exaust restriction at all. Then you pushed the switch inside the car closed and the flaps closed and the car went back to normal sounding.
Great for street racing. Reaaly loud when open though. I did it on an old Chevy 350 in my '79 z28 and an oldsmobile 455 in my '74 cutlass. Freaking deafaning when you got on the culass with basically open headers.
Damn I miss that stuff... Now I'm just happy when my car gets me to work with no trouble.  |
Those are called "cut-outs" and are utterly pointless on any V style motor without forced induction. A V style engine is designed to scavenge the exhaust puffs from each cylinder and syncronize the two banks for a more efficient, smoother running engine that makes more power. A true performance exhaust system has both banks combining behind the headers by and X pipe for the scavenging effect. You can put cut-outs after the X pipe to decrease the back pressure a bit but you really gain no horsepower. You lose horsepower and efficiency by putting cut-outs on a V style engine before the X pipe. It causes a rough idle and an incurable inbalance in the engine. A forced induction vehicle does not require scavenging as it already has pressure in the intake and has a ton of back pressure in the turbo. Also, most cams designed for forced induction motors do not rely on scavenging and are built with a more aggressive low end powerband.