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Mild street 440 4bbl...question is should I run 2 1/2 or 3in exhaust? Tri-Y Schumacher headers is what I already have. Also should I install a "H-pipe" ? What does it do? I've heard both yes & no about a "H-pipe". Thanks
2-1/2" pipes with a 2-1/4" or 2-1/2" crossover("H") pipe. 3" pipe in a dual exhaust system is overkill for most streetable engines & will actuall hurt velocity.
Mild street 440 4bbl...question is should I run 2 1/2 or 3in exhaust? Tri-Y Schumacher headers is what I already have. Also should I install a "H-pipe" ? What does it do? I've heard both yes & no about a "H-pipe". Thanks
H-Pipes inherently improve low-end torque by balancing exhaust gas pressures between the the sides. Most push-rod motors can benefit by using an H-Pipe.
X-Pipes tend to blance the flow between both sides and can increase horsepower on higher revving motors. The modern modular motors see benefit from the X-Pipe design.
Larger pipes are not always benficial to exhaust/horsepower/torque. It is all a matter of flow. It is possible to inhibit flow by using too large of a pipe. I would think the 2-1/2" would be more than adequate in your application.
i understand the concept of easier routing of the pipes keeping them smaller and the concept of not adding unecesary weight with pipes bigger than they need to be,go with whatever size the collectors are no point in building bigger or smaller and i still havent seen a prostock car with an X or H pipe.
whatever the collector size is, is usually optimum,"open", w/ some collector tuning(length) if u ran the same size as the collector thru some configuration of pipe and the same size muffler, it still would be below optimum for full h.power for those headers. mine will be 3 1/2" , thru 3 1/2" turbo inserts, w/ a set of 3 1/2" straight thru shortys that only drop the decible level by about 2, figure both will be quieter than a 3 1/2" flowmaster, and flow way better, won`t have but a $120 tied up in all of it, not counting the headers. will be interesting!!-bob:burnout::burnout:He is not building a prostock drag car now is he?
by the way, 68 hemi roadrunners came out w/ an h pipe "stock".whatever the collector size is, is usually optimum,"open", w/ some collector tuning(length) if u ran the same size as the collector thru some configuration of pipe and the same size muffler, it still would be below optimum for full h.power for those headers. mine will be 3 1/2" , thru 3 1/2" turbo inserts, w/ a set of 3 1/2" straight thru shortys that only drop the decible level by about 2, figure both will be quieter than a 3 1/2" flowmaster, and flow way better, won`t have but a $120 tied up in all of it, not counting the headers. will be interesting!!-bob:burnout::burnout:
"Mild street build" 440.
Would need more on the cam to plug into 'pipemax' but from past experience I can tell you that discplacement plus power band rpms are primary factors in determining the sizes needed. Guessing that the rpms of interest and peak Hp is below 6000, probably below 5500, would favor a smaller diameter (like 2.5"). 3" is a big jump up in terms of cross sectional area. I'd not do that without more data or as an experiment. If so, I'd test it from the collector to the first interuption (H- pipe, X pipe or muffler).
H-pipes and x pipes are somewhat useful for 'sharing' the mufflers, but measurable value seems to depend on placing in the right location to create harmonics that help in the rpm range of interest.
My guess is the factory either found a performance advantage with H-pipe and/or used it to break up a drone resonance.
Originally Posted by 1Fast340
i understand the concept of easier routing of the pipes keeping them smaller and the concept of not adding unecesary weight with pipes bigger than they need to be,go with whatever size the collectors are no point in building bigger or smaller and
i still havent seen a prostock car with an X or H pipe.
Velocity is what you want to achieve through the system. The fact is that too large of a pipe diameter will actuall hurt velocity. Remember that we have to blow all the exhaust through a set of pipes nearly the whole length of the car through 2 at least partailly restrictive mufflers. Too big of a pipe causes the velocity to drop. Another thing is in an efficeint exhaust system the exhaust gases need to be kept hot all the way through the system until they exit. Hot exhaust gases move faster. Smaller pipes keep the heat in better & therefore the gasses move faster than a larger diameter pipe would. The natural movement is from a hotter area to a cooler area- heat disipation helps flow. That why racing headers are thermal coated on the inside & the outside. To keep the heat in the gases longer & keep it flowing. What you don't want to happen is the gasses expand & lose their heat before they exit the system, then the velocity stalls & you just have a wall of exhaust that has to be pushed out of the system.
Any body ever run or seen at the track guys running Torque Tubes on their open headers to run quicker? Same theory.
Unless you are running a fire breathing dragon on the street, 2-1/2" exhaust should be plenty in a dual system. If it were a single system then 3" is good.
The system with the highest velocity would be the system with the least restriction. What changes in air flow in the header collector that doesn't happen in the rest of the system?velocity is important for primary tubes on the headers,collector sizing is also important but after the correct collector lenght has been achieved all you want is minimum restriction.
disagree on 2 1/2" pipe. had 3" on a stout 406 sbc,had tail pipes put on it, out behind the rear wheel wells. wasn`t mandrell bent. ( BENDS CAME OUT ABOUT 2 1/2"). I could tell the diff. when I started it and backed it out of the muffler shop. put about a hundred miles on it, pulled them off, went w/ two 3" into 3' flowmasters, then dumped before the rear wheels. get this, those tailpipes made almost 3 tenths diff. on the dragstrip!i have a 440 in my dart with a 2.5 h-pipe exhaust system and tri-y schumaker headers. its works pretty nice