this is why TTi headers suck for power
Crackedback - Thanks for the cool link. Awesome sounding engine.
FWIW, some general rules of of thumbs regarding headers.
1. The tube diameter determines the rpm of the torque peak. Larger diameter higher rpm for the peak.
2. the length of the tubes determines the torque shape on either side of the peak. Longer tubes favors the torque belwo the peak and shorter tubes above.
3. The collector diameter is the same as tube diameter. Collector has the same impact as tube length.
The impact of Tri-Y and step tube designs is greatly influenced by other parameters in the combination. They could help the mid range or not have any significant impact.
dgc333 - thanks for the explanation. Simple and I think I get some of the principles now. Now I know that headers are only 1 part of the engine breathing cycle, so air filter, carb, intake, heads, and the rest of the exhaust have impact. But considering your principles.....
Let me see if I get the theory right:
Example headers
- Header A = 1.75 " dia tube, 25" equal length, Collector 3" dia 10" long
- Header B = 2" dia tube, 25" equal length, collector 3" dia, 10" long
- Header C = 2" dia tube, 30" equal length, collector 3" dia, 10" long
"A" compared to "B" --"B" will have its torque peak at a higher RPM than "A". Absolute torque values between the two may vary based upon the rest of parts in "breathing" cycle. "B" may have a be higher torque value than "A" ...or not. It just depends on the individual components.
"C" compared to "B" --"C" will have a "flatter" torque curve BELOW the torque peak RPM (torque builds faster before peak) while "B" may have a "flatter" torque curve ABOVE it (torque falls off slower past peak rpm). Both should have a nearly identical peak RPM but again absolute values may vary.
I know this stuff is a bunch of theory... :read2: but I like to understand some of the thumb rules so I can more easily evaluate marketing hype by different header builders for my engine's mission and not fall into the "bigger" is better trap.
By the way...in the next couple of days, I'm about to fire up my 340 x-head with new TTi headers in my '65. :toothy7: I think they will do better than the slant-six cast iron exhaust manifold I used to run.