Exhaust headers, LS series engines

[Classic Revival]

We base ALL our work on SOUND ENGINEERING PRINCIPLES & experience, not someone’s opinion. In this case the branch of engineering is called Fluid Dynamics.
For an internal combustion engine to achieve a high efficiency, the flow through the exhaust MUST be laminar. If you increase the dia of the exhaust header the flow turns turbulent & the efficiency decreases. Even on the race car ( which produces far more HP & torque than you will see in a Cobra road car ) the primary tubes are still 1 5/8 to maintain the low down ( below 4000 RPM ) torque. Yes, there is a slight trade off in HP at high RPM, but this is only very slight.

Your “opinion” seems to be based on what the so called “expert tuners” (who are not worth a pinch of ****! ) do. They are great at tuning vehicles to run at full throttle opening, but not at making them driveable below 4000RPM which is where the motor will spend most of it’s time on the road. A good example of this can be found on another thread on this forum where one of the US tuners gives dyno results of their cam etc in a LS1, it produces some 510 HP. However, if you look at the dyno graph, ALL of this HP & torque is produced between 5500 & 7000RPM !!! It has in fact a slight DECREASE in power & torque at low RPM !!! – not what you would call a “drivable” unit.

For a good drivable vehicle you need a broad spread of torque across the rev band not something that is very “peaky”& this is why we stick to the smaller primary tubes.

Our vehicles speak for themselves, be it road or track, they are on top because they are based on SOUND ENGINEERING PRINCIPLES.

Cheers,
Ian