i watched clark's post (http://www.jalopyjournal.com/forum/showthread.php?p=642787#post642787) closely about his tri-y headers. there is mention of torque/power ranges in there. sounds like tri-y will give more low end torque and 4 tubes less (and, i assume, more high end HP). what about zoomies? could someone please fill me in. i don't need (and wouldn't understand) why it's like this. i'm just looking for what actually happens. i.e., low vs high rpm torque & hp for various types of exhaust systems. i have been thinking all along that i would use zoomies w/ baffles on my nailhead T modified. i want as much low end torque as i can get so i can cruise (highway speeds) at low rpm. i had never considered that different exhausts would change the torque curve.
Sounds like you have it about right actually. Tri-y usually builds more mid & low end, 4 into 1 usually a little more top end. Zoomies are just a "get it out of the way" type system. When zoomies are used (not counting rodders) it's just 'cause the restriction by the exhaust (header) negates any airflow/exhaust tuning gains. Usually you see zoomies on blown motors, so one could assume that the exhaust pulse tuning is less impotant on pressurized engines... Hope that helps. That being said, my naturally aspirated 6 carb Olds will have zoomies anyway.
I've been told (and I can't verify this -- don't know my header science) that due to their firing order, nailheads really like a tri-y design. Exhaust pulses and scavenging and all that. Anybody understand this stuff better? Steve.
For the street,smaller diameters work better. Some basic header theory: http://www.ssheaders.com/header.htm If I really wanted Zoomies,or Weedburners,I'd probably make them double walled.Small pipe on the inside,with baffles,to try and get back some of the torque lost because of the short length,and BIG pipe on the outside for looks.
Unless you have a race motor, scavenging is not good. You are actually robbing power on a street engine.
bluthndr pretty basically has it on the try-y verses long tube headers. the problem with trying to actually tune a long tube header on a v-8 is that to actually scavange properly they need to link cylinders that are fireing 180 out. On most V-8 mills that would involve pulling a tube from the opposite bank. That basically becomes a mute point if your running through mufflers as they have a tendency to break up your pulses. Zoomies are really peaky, very narrow RPM band. A lot like a long ram intake. its because you're seperateing your cylinders. It involves major exhaust engineering, something that I have to admit is lost on me.
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