Headers vs 340 manifolds

junkyardhero said

what's the % torque difference per ci under the curve with each 2* coming and going? is there a dyno chart for that? or possibly a formula?

Click to expand...

From the few LSA shootouts available, I noticed about an average of about 3-4 lbs-ft per degree of LSA, and wider than about 110 seemed to be an bigger average than narrower than 110. And given hp is less than a 100% under 5252 rpm were talking a couple of hp per degree for these engines.

Not saying 3-4 lbs-ft can be considered a rule of thumb for all builds.