exhaust manifold interior dimension

[aga]

good day guys. i'm researching into making my own exhaust manifold (T3 for a borgwarner) and the supplier has two similar dimensions... one is 42.16 mm diameter with a 2.7 wall, the other 42.4 with 2mm wall. obviously its good to have thick walls on the manifold, but the resulting inner diameters are 36.6 on the one, 38 on the other. which diameter better fits the SR20? does anyone know the area of the head port? one head flange from a website is offered in 1.5 inch diameter which is 3.81mm...close to the thin walled pipe. any ideas?

[Mikester]

Put an I.D. dial caliper into one of the ports and measure it out.

The runners of my manifold are 38mm I.D.

[aga]

thanks man!

i found another supplier that has 42.4 external diameter but with 2.6mm wall. which results in a 37.2 internal... unfortunately i cant remove the manifold just to get a measuring, i wanna gather all my parts before i strip it down.

anybody got a head, or a head flange? ideally, anybody got a drawing of the head flange with dimensions to give me? :D