pm sent.

Thanks Ernie
So assuming you had a very stock A15 (cam, head,carby etc), do you think there would be a noticable improvement between an H99 and a GX exhaust manifold?

Also how did the C22 Vanette "dropdown" manifold compare with the H99?

Enlargerning the outlet on the H99 has supposedly some improvements and one Ill be going for and can be done by a good welder.

Starting from sanblasting a H99, heat to 400 celcius then build up with bronze on the walls near the outlet lastly enlarge the outlet or as Ive seen on a Midget datsun powered race car just the flange area cut and shut with a bigger one from something else.

Not sure on the performance improvement but the Midget cut and shut is still going strong for last 14 years.

yes mal. i have flowed all of them & all flow different. heads & manifolds.

GX stuff comes out on top (head & manifold)

note; also depends on other things aswell

Have any of the Datsun Gurus out there ever measured the flow/ efficiency/ power difference of the various factory Datsun exhaust manifolds?

I am guessing the GX is the best otherwise the speedway guys and gals would use something else.

Is a 1200 GX (dual outlet) significantly better than the 3 bolt 1500 (single outlet) H99 Sunny/Vanette item?

Could it be that the Nissan engineers simply switched to manufacturing the single outlet on later A15s to reduce the cost of exhaust pipes?