We found we needed a 2 inch internal diameter "minimum" on these heads to clear the port, thats 2 1/8 pipe with 1/16 wall tube. 2 1/4 O/D worked well in our application (ported -13's and 572ci) but was still calculated as on the "small side"
I think the ideal was a 3 stepped header 2 1/4, 2 3/8 2 1/2 into a 4 1/2 collector. You'll be leaving something on the table with the TTi's cause of the 602 Ci and N2O, imho.
BTW Indy does an exhaust gasket for these heads around $20 each
http://www.indyheads.com/images/p_pge/price23.pdf
Port sizing is listed as 2.200 x 1.820.

Last edited by Tig; 01/09/09 02:07 PM.