Unfortunately about the only thing I can say about the RPI headers is that they fit....
I know the chap that originally commissioned them...
I've fitted a set, tested them, and then removed them, threw them away and fitted a Librands manifold....
Instant and measurable performance increase...
Simon @ SiFab.co.uk
Interesting. Did You test them by the seat of your pants, or a rolling road? I used a rolling road to test the complete engine but did not have comparative information on other headers. The results were not spectacular. I have since replaced My 3.5 engine with Buick 215 heads with a Morgan 3.9. (sourced from Bill Fink) Very much improved.
