I need to calculate the optimum length and diameter of the exhaust manifold primaries,
I have had a couple of offers to run the numbers but no joy yet.
Anyone know of a serious excel calculator that uses cam timing and duration, rod length, stroke etc.
Or has one that they could email.

these any good to you?

http://www.wallaceracing.com/header_length.php

http://www.custom-car.us/exhaust/header.aspx

http://www.strikeengine.com/performance_car_parts/exhaust-manifold-design.html