Thanks for your input I really appreciate it when someone with your knowledge especially with turbos can shed alil light on these type of topics .Before you weld your wastegate feed pipe, make sure you loosely install the wastegate, so you can determine the dump angle and if there's going to be any interference with surrounding components. That would really suck if you got it all fabbed up only to find out the wastegate won't clear this or that. Kinda the measure 4 times cut once method. Also, I'm glad to see you decided to plumb it under the turbo, so that both banks are feeding the wastegate vs just plopping it on the cross over pipe. Sure that worked for a lot of us years ago, but with better flowing cam/heads and more efficient turbos, mounting it on the crossover it no longer a 100% sure bet. Chuck's wizardry welding of that stubby feed pipe directly onto the turbine housing would be nice, but I would keep an eye on the welds overtime. That much weight of a large wastegate hanging onto the turbine housing at insane EGT's would take a tole on it over time. Think metal fatigue. But it would be in an extreme constantly raced case, not something that you'd occassionaly race.
A lot of guys have been using the .81 A/R T4 Tangential turbine housings with great results over the years. With your CI size, the .96 single inlet Tangential style turbine housing would be GTG. A good PTC or Husek converter will be required once you start initial testing. And having a BB turbo will help the transient response and spool up on the initial hit. Tune will help finalize the spoolup curve as well. When I was spec'ing back in the day, if the combo was under 270", I would recommend the T4 .81. If 274+ and racecar, the .96 would be the starting point. High hp (over 1200 fwhp) would change it from there. You mentioned a 6871 turbo and the CI size, so I'm guessing this will be a street car with some active street antics involved. Is it safe to say you're looking for 850-950 rwhp with 1:1 - 1:8ish BP goals? If so, look closely at Gen 2 CEA turbine wheels and BW's top of the line turbine wheels. But you probably already know this so I digress.
Others have dabbled with divided T4 twin scroll housings with larger A/R's. Most of those guys keep their results COSMIC TOP SECRET though. There are limitations to what the normal size T4 housings can do, as evident by the larger T4 "mid" frame turbo combos out there. IE: the old TSL class and current TSO class combos.
Yes and luckily my converter guy is local and is really cool with doing restalls for me . It’s a pain getting it out but I’ve done it to many times to count so if I I’ve gotta yank it again what’s one more time to add to the count also thanks for your input aswell nickIf you are not satisified with spooling/response, you could get the converter re-stalled higher.