headers....should be run with true duals only?

[BigRed76]

After reading the section submitted by nbpro, I am much more informed about exhaust pressures, and I apoligize for sounding like an idiot about the open header thing. But when it comes to the scavenging effect, wouldn't a full exhaust help create more negative pressure due to more exhaust volume compared to the open headers? or am I just overthinking this?

[piecesparts]

Originally Posted by cableguy0

backpressure is a myth. It has nothing to do with the exhaust. bigger pipes will make more power period. header tube size however is very important. due to scavenging.

Many exhaust companies will argue this point. There is a limit as to what you want for pipe size and what the larger pipe will actually do for or to you. Too large and the scavenging effect will die off way to soon and hinder your performance. the thought is that one should look at the driving that they do and build to that requirement. 3" pipes on a standard small block engine with minor mods is a loss of energy and the exhaust will be hampered by the fact that as the exhaust cools it will not pull the exhaust from the engine's cylinders, so loss of performane will happen. There are things that will enhance the scavenging effect and the removal of gases, such as the use of an X-Pipe, over straight true duals or even an H-Pipe. Be careful not to overdo the pipes and make the efficient and the gains are there.

[mooseknuckles]

Your definately over-thinking this! do you want headers or not? If your
looking for more power you're gonna need them eventually!.... That sounds like a lot of money tho....

[nbpro]

http://67-72chevytrucks.com/vboard/s...d.php?t=418781

[BigBlocksRule]

Several good points in that discussion, the most important being that exhaust pipe size is critical to the entire system working correctly. As the exhaust gasses cool, they shrink. If your tailpipe is the same size as the header collector, these shrinking gasses will slow down, losing velocity and inertia. If the pipe is stepped down in size, they'll lose size but since they still fill the pipe, the exhaust gasses don't get "lazy" and slow down, they maintain close to the same speed as just behind the collector.
Lesson: Don't go with huge pipes, they'll hurt performance.
BTW, in the muffler tests I've seen, the Walker Hemi Turbo made a couple of hp more than straight pipe and they sound GOOD

[piecesparts]

When I built my 383 stroker engine, the engineering tech at Flowmaster was a great help. We discussed the fact that the size was important and he told me, that unless I had a large bore thumper, the 3" exhaust was a loss for my driving needs. He gave me info that supported what I use today and I believe that I am doing well with the systems that we dreamed up. I would like to go to a system with an X-Pipe design, vice the H-Pipe that I presently run, but that is down the road.

[78 Chevyrado]

Originally Posted by BigBlocksRule

^ kinda tough to mix those two up, they're actually the opposite thing...

tough is relative... Ive been told I have a nice Ranger before..

A nice short article that makes sense.
http://www.dsmtuners.com/forums/freq...kpressure.html

[nbpro]

Correct me if I'm wrong, but routing has a lot to do with it too doesn't it? For instance, routing your pipes over the rear axle. Could this not help in cooling the gases?

[jasonroman]

well i think what im gonna end up doing is, running what i have.
i ordered the header buddy...3 to 2.5. hopefully that will hook up to my existing y pipe and i can go from there.
i just cant see spending another 5-800 for redoing my exhaust to tru duals. and since my motor is a vergin and has nothing as far as mods. i guess i dont need the duals yet.
xmas is around the corner. 2 kids, on that happens to be born on xmas...= no money for playing with truck
hopefully this goes on ok and not too much.
later on i will, or shall i say plan to, change carb, intake mani, and maybe a lunati cam? not that it will be a race truck then, but ey, gotta go little by little.
i would love to have the duals, but i think i should match duals to a big boy motor. and since i have little kid dollars, things will be what they are.
thanks for help and advice.

[slugish]

Originally Posted by jasonroman

well i think what im gonna end up doing is, running what i have.
i ordered the header buddy...3 to 2.5. hopefully that will hook up to my existing y pipe and i can go from there.
i just cant see spending another 5-800 for redoing my exhaust to tru duals. and since my motor is a vergin and has nothing as far as mods. i guess i dont need the duals yet.
xmas is around the corner. 2 kids, on that happens to be born on xmas...= no money for playing with truck
hopefully this goes on ok and not too much.
later on i will, or shall i say plan to, change carb, intake mani, and maybe a lunati cam? not that it will be a race truck then, but ey, gotta go little by little.
i would love to have the duals, but i think i should match duals to a big boy motor. and since i have little kid dollars, things will be what they are.
thanks for help and advice.

Very reasonable & responsible thinking on your part . You definitely have your priorities straight.