What I don't understand yet is, what is the impact of a 1 3/8 on a stock 3.0 with dual weber or zeniths ? Is the performance increase, even on the smaller 1 3/8, only noticable with DCOE40/45 ?
This is my question also. Will "strapping on" a pair of 1 3/8 headers to an otherwise stock 3.0 or even 3.5L B34/B35 motor with dual carbs yield any positive results and if so where in the RPM range? I reviewed the Chevy chart and understand the concepts, but is the OEM BMW exhaust (exhaust mani's and dual downpipes) that constricted that headers will free it up? If the headers are that much more efficient, will the motor run leaner? What changes, if any, will need to be made to the fuel delivery once the headers are installed?
I think, with a stock M30 motor, B34, B35, etc., there is potentially more bang for the buck/better performance gain with a hotter cam like a 284 still exiting through the OEM exhaust. You mod the exhaust last after you address the fuel (carbs or FI) and cam and even then, you need to be very careful how the exhaust is configured so you don't lose low end torque which, I think, is what most folks here are after.
That'a my hunch with no data to back it up and I could be totally wrong. I'm just trying to understand better.
That all said, I am considering the headers group buy as well but I have a cam and Weber 38s installed on my 3.3L already.