exhaust pipe sizing

[cooter55]

1973 454 (049 heads) Mild roller cam, long tube headers with 3" outlets, MSD ignition with 6A box, performer 2.0 intake, and fuel injected. Right now I'm running two 3 inch pipes out with Purple Hornies mufflers. This is just to get me to the muffler shop. The question is...What size pipe would you run for a new exhaust? I probably will put a pair of Flowmaster 40's on with an X-pipe and exit ahead of the rear wheels. Is 3" too much? Would 2.5 or 2.75 be better? I'm not worried about loud, just want to do it right the first time.

 

[scottybaccus]

1973 454 (049 heads) Mild roller cam, long tube headers with 3" outlets, MSD ignition with 6A box, performer 2.0 intake, and fuel injected. Right now I'm running two 3 inch pipes out with Purple Hornies mufflers. This is just to get me to the muffler shop. The question is...What size pipe would you run for a new exhaust? I probably will put a pair of Flowmaster 40's on with an X-pipe and exit ahead of the rear wheels. Is 3" too much? Would 2.5 or 2.75 be better? I'm not worried about loud, just want to do it right the first time.

2.5" duals is plenty.You don't have tons of intake flow, so don't get carried away on the exhaust side. Additionally, you have a big block for torque, not rpm, so big flow will just kill all the torque that engine makes, and you will shoot yourself in the foot down low. Remember where you drive it at: 1800-4500 rpm.

 

[cooter55]

2.5" duals is plenty.You don't have tons of intake flow, so don't get carried away on the exhaust side. Additionally, you have a big block for torque, not rpm, so big flow will just kill all the torque that engine makes, and you will shoot yourself in the foot down low. Remember where you drive it at: 1800-4500 rpm.

That supports what I was thinking. Thanks for the response