GTR not quite the same and then you have heat to consider as well not to mention limited space Hopefully someone will buy these ones from ebay and prove me wrong
If mine wasnt back in the car id probably give them a go, allthough they do look quite easy to make so id probably make them. The difficulty with back to back testing is that nobody is really going to remove their motor just ot install them and do no other mods. But yeah id love to see some results too
Stainless has too high a thermal expansion coefficient to be used in a log manifold. This causes high stresses around the welds and will eventually lead to cracking. Stainless can be used in equi-length manifolds because the stresses can be managed by the design of manifold. That's why Pentroof use the "softer" 304 stainless as compared to the 321 because it allows to stresses to be lower.
My opinion... buy one of the currently available cast manifolds. You might get away with it on a sky or silvy, plus if they do crack it's an easy fix but not with a 300 it's engine out more then likely and there goes your savings using SS. If supported and braced properly the chances of cracking are lower, but SS is so hard to stop from cracking in these sort of applications.
my bestie has stainless manifold off ebay on his rb20det, had them on his car for like 2 years now, and car is making 260rwkw with a t3/71r turbo no drama''s no cracking, i have a set of xspower extractors for my n/a they look ok, yet to fit though
did anyone actually read the link I posted? I know they arent 300 manifolds but if they do that on 4G63's then why would you even consider them for a 300?
IMHO if you aren't going to go with the current cast iron manifolds that are available for relatively cheap, then you definitely aren't going to go to the expense of Pentroofs or similar, so the only option I can see is to make some yourself.
