Sidepipe horsepower loss?

[blykins]

You will make it infinitely louder if you keep reducing the amount of "stuff" that's inside of those pipes. It's not really the packing anyway, it's the ID of that hole going through the muffler.

However, restrictive sidepipes have been shown to take 100hp, so what do you do, right?

Sidepipe mufflers would be the easiest route probably.

I wouldn't swap the intake as a smaller inch motor wouldn't most likely gain a tad bit of power on the very top end, but lose a lot of low end and mid range power.

If I were going to get into the heads, I would swap brands altogether. The Procomp stuff flows like factory iron...very restrictive. You could pick up 50-75hp by going to a nice head like an AFR or Brodix.

[RICK LAKE]

rdc767 Ron Side pipes can cost from 0-60HP depending on the motor. 12.5 A/F is fine for WOT but not for cruising down the road. You want about 13.1-13.5 A/F. Exhaust is a black magic thing. You want just enough back pressure to help control heatout of the heads and not burn the exhaust valves. Back pressure you are looking for about 1-2 psi+ at Cruise speed of the car. This will jump to 3-5 psi under WOT. The motor doesn't live there all the time. If the car is going to be street and the size of your motor 2.5" in and outlets are fine. If you go to 3" the noise will increase and you will need ear plugs for any cruising. Race pipes are wide open side pipes. I have both. The less the back pressure the richer you should run the motor to prevent burnt valves. Open pipes will hurt bottom end power and only get small gains at 5,000 rpms and up. If this motor is built for torque, it will fall on it's face. If it's a high HP motor in the 5,000-6,500 rpm range than bigger is better. Just watch out of the noise police. Ps that ringing in your ear will stop after a couple of hours. At least the other half can holler at you and you will not hear a thing from the left side. As far as the other question, it's about matching parts. You need to find out where the power curve of the camshaft is and work from there. With the size of the motor a single plane torker manifold that is ported and flow checked would be the way to go. I would send this manifold to Joe. Craine and let him do his magic to balance out all ports and flow of the manifold. Some ports can be 5-30 cfm off other ports. This means less air and fuel getting into that cylinders. His work comes back looking like thing to be put under glass. There are small power gains too. Depending on manifold from 3-25 HP and a little less torque. keep this motor streetable. If you have the HP bug, build another motor and race pipes for the car. This way you always have a spare bullet for the car. Your motor is a 400+ HP motor, drivetrain drain is about 15-18% and side pipes another 10-30%. Re work exhaust and intake and retest. Good luck Rick L. One last note, (BIGGER IS NOT ALLWAYS BETTER, JUST BIGGER) this is for exhaust and tuning it.

[Jeff Frigo]

Originally Posted by RICK LAKE

rdc767 Ron Side pipes can cost from 0-60HP depending on the motor. 12.5 A/F is fine for WOT but not for cruising down the road. You want about 13.1-13.5 A/F. Exhaust is a black magic thing. You want just enough back pressure to help control heatout of the heads and not burn the exhaust valves. Back pressure you are looking for about 1-2 psi+ at Cruise speed of the car. This will jump to 3-5 psi under WOT. The motor doesn't live there all the time. If the car is going to be street and the size of your motor 2.5" in and outlets are fine. If you go to 3" the noise will increase and you will need ear plugs for any cruising. Race pipes are wide open side pipes. I have both. The less the back pressure the richer you should run the motor to prevent burnt valves. Open pipes will hurt bottom end power and only get small gains at 5,000 rpms and up. If this motor is built for torque, it will fall on it's face. If it's a high HP motor in the 5,000-6,500 rpm range than bigger is better. Just watch out of the noise police. Ps that ringing in your ear will stop after a couple of hours. At least the other half can holler at you and you will not hear a thing from the left side. As far as the other question, it's about matching parts. You need to find out where the power curve of the camshaft is and work from there. With the size of the motor a single plane torker manifold that is ported and flow checked would be the way to go. I would send this manifold to Joe. Craine and let him do his magic to balance out all ports and flow of the manifold. Some ports can be 5-30 cfm off other ports. This means less air and fuel getting into that cylinders. His work comes back looking like thing to be put under glass. There are small power gains too. Depending on manifold from 3-25 HP and a little less torque. keep this motor streetable. If you have the HP bug, build another motor and race pipes for the car. This way you always have a spare bullet for the car. Your motor is a 400+ HP motor, drivetrain drain is about 15-18% and side pipes another 10-30%. Re work exhaust and intake and retest. Good luck Rick L. One last note, (BIGGER IS NOT ALLWAYS BETTER, JUST BIGGER) this is for exhaust and tuning it.

Rick:

Great job, I am taking my car to the dyno next week with my new Howe 3002 3-2/3" mufflers. There is a seat of the pants difference. I will post the numbers.

[Rare Iron]

Remember, engine must be able to exhale properly. Build power up at the engine, it must be able to get out downstream without excessive backpressure. Right diameter = flow velocity. "Stock" type mufflers with under a 2" flowpath going through them is just idiotic. I wouldn't run that diameter on a '67 Mustang 289 2bbl.

-Eric