I'm just wondering, do you get any remarkable changes with dutra dual cast iron manifolds?? do you get any better sound??
I have 2 or 3 cracked exhaust manifolds in the garage, is it worth the trouble?......by the way how much do headers cost in usa?
I asked a speedshop here in finland for SL6 headers and I almost fell off the chair, 1100 euros!!!! Is that expencive or what....

The Dutra split manifolds will give you 4 to 10% increase in power (or milage) depending how you set-up the rest of the exhaust system.
You will get a different sound because each cylinder firing (pulse) is always in the other manifold, you have more seperation time between the pulses in the manifolds.

If you have some cracked manifolds and know someone who welds cast iron, you can make a set of split manifolds or the rear manifold without much trouble.
DD

This is another Dutra Duals question. I new head casting that I am going to set up with porting, 1.70"-1.44" valves and mill for 9-1. I realize the stock manifold studs and retainers have been working, more or less, for decades. I would however like to retain the intake and exhaust separately and not have any vacuum leaks. I noticed the newer Dutra castings have a pretty full flange and have been thinking about getting a set and redrilling them and the head for two bolts/studs per cylinder with the studs centered above and below the ports. There is plenty of material on the head casting for this. The bottom studs might be a little hard to reach, but I am hoping it can be done with the right length studs and 12 point nuts. The offy intake I have has enough material in the flange to redrill and spotface for 1/4" or 5/16" socket head bolts. I would plug the stock holes with stainless set screws. Has anyone tried something like this? One deciding factor will be access to the bottom studs.