Header Primary Length Calculations - 3500

[Scott_68B]

I've been playing around with my Headers By Ed information and the primary length calculation Ben/Brad posted here:

http://wiki.60degreev6.com/index.php?title=Headers

I'm using the formula detailed at the above link to calculate what the primary length for a stock 3500 would be. I'm using the following but I'm not sure what d should be:

Stock 3500
A=197
S=3.31
D=3.7
d=????

Has anyone calculated what d should be for the d shaped exhaust ports on a GEN 3 head? Also, the Headers by Ed web site seems to have disappeared, does anyone know if they are out of business now?

Thanks

-- Scott

[Superdave]

I came up with around 32" primaries for my 3500. So far they seem to be working very well..