LB7: Safe RPM

[DAVe3283]

OK, I have been looking here and around the internet for a while, and I can't seem to find a good answer.

What is a safe maximum RPM for a LB7 with just tuning? No internal engine mods, just EFI Live.

EDIT: Found this [thread=17189]thread[/thread] by searching with Google. For some reason I couldn't find that with the site's search...
They seem to say the stock valve springs are only good to ~4000, but: what's the difference between WOT @ 4000 RPM and grade braking @ 4000 RPM? Because doesn't the truck push past 4000 with big trailers?

And, for future reference, what mods would have to be done to support 4800 RPM under power? Or would there not be a point?

Any info is appreciated! Thanks guys.

 

[LBZ]

Some people have done dyno testing and haven't found any gains to running it past about 3500-3600 rpm with stock parts. I run mine up to 3800rpm on the track but that's just to keep it from shifting after the 1000' mark and haven't done any damage.

 

[Dozerboy]

X2 but I'm not sure if thats true with the IHI turbos. I have fuel to 4400, but all my shift point are 3500-3600.

 

[S Phinney]

There really isn't a need to run the engine that hard unless you have enough air and fuel along with the accompanying parts to make use of it. A 66mm turbo is only good for around 3450 rpm before air flow gets out of its efficiency range. There wouldn't be a gain in running beyond the efficiency range.

 

[DAVe3283]

Thanks for all the everyone. It looks like I won't get any useful power after 3500-3600RPM because of the stock turbo.

Anyone have any idea about the valve springs? I am curious if there would be a difference with the engine fueling around 4000 RPM vs. compression braking (grade braking) at 4000. My initial impression is that the occasional WOT run to 4500 (ignoring the lack of power) wouldn't do any more long-term damage than an equal run to 4500 while slowing down on a hill.