Newguy1998
Member
IMO the GMx turbos are fuel wasting scrap metal. There are far better performing turbo's out there above and beyond the large turbo I run. A start is the article below and many other discussions of other turbos abound on here.
http://www.maxxtorque.com/2012/07/the-65l-diesel-factory-equipped-asthma.html
FYI Pre-cups are almost a forgotten black art. Different precups will make the engine run like it needs a tune up: severe bolt loosening vibration that may be bad enough to break the crankshaft. Precups control the flame entering the combustion chamber as far as speed, when peak pressure happens, fuel limits, economy, emissions, etc. Different precups would be like firing one side of the engine several degrees off the other side and this would vary by load and throttle. The smaller precups can even hit their limits with fuel blowing so fast they centrifugally separate the air fuel charge: thus you have half the engine making more power while the other half smokes black. (I doubt you are pushing that much fuel w/o a turbo upgrade.)
You absolutely got lucky with getting a pair of diamond precup heads.
I'm well aware of how bad GMX turbos are but, like I also mentioned earlier, I don't have the funds at this point to upgrade it. I'm happy I found one for relatively cheap so that I can at least get back on the road. It being worn out was an unexpected expense. I mean, I was expecting some extras, just the turbo wasn't one of them. Replacing both heads was unexpected also, still can't believe I lucked out there.
Anyway, thanks to everyone that contributed, I couldn't have done this without you guys. I'm going to start putting everything back together tomorrow once the gaskets & bolts come in.