Quote:
Originally Posted by BabyDiesel
The math worked like this for me - A 1.5" primary SBC Header will have a primary cross section of 1.767". 25% of this would be 1.325". Since there is a greater focus on low-end, I believe Tim could go slightly smaller. A 1.25" primary gives ((0.625" x 0.625")3.14), which equates to a 1.227" cross section, a 30.6% decrease.
So 1.25" seems to be the front runner  unless there is some specific exhaust information that we are missing...
Edit: Tim posted right before me. Throw all this malarky out the window!  |
CFM is the key metric. The SBC with 1.5" primaries is likely trying to improve torque at relatively high RPMs. The large displacement and high revs will mean a very high rate of flow.
Designing a header for a small displacement Geo engine running at low RPMs, and part throttle will need a very different design since the CFM is so low. If this header ever gets built, be aware it will significantly restrict high RPM performance.