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Big cams improve power at higher RPM. To take advantage of big cams, you'll need to rev the engine a lot higher.

I'm not a 2J specialist so I don't have any 2J-specific experience to share with you, but I'm guessing those cams with 230* or more of duration @ 0.050" will make peak torque at 6000rpm or more...

...probably not what you want for anything less than an all-out build.
 

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whenever i see post about NA builds i think of this: Naturally-Aspirated 2JZ-GE '95 Toyota Supra with ITB's all that work and money for 260Hp.
I was reminded of that article as well. Thanks for providing the link so I could review it; it's been a couple years.

I know 260whp isn't an amazing number these days, but it's still 87hp per liter - at the wheels. Probably 100bhp per liter, or very close to it. That is pretty legit. A really well-tuned 6.2L LS3 with all the goodies will usually come in around 475whp - which is only 77whp/L or about 88bhp/L - and that's with a LOT of cam timing coupled with fabulous cylinder heads and intake manifold...

Also, who knows how well-matched the header, ITB intake and valve events match eachother? You can usually get ~110-115bhp/liter at or below 9000rpm with a nicely matched head/cam/intake/header setup.
 

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What are you after with this project? Daily driver? Fun fair -weather toy? Track days? Something else?

My original plan was to drop an LS3 into a nice IS, and make it near-OEM. In my search for a nice IS, I came across a good deal on one already turboed.

It's a fun toy and I definitely enjoy playing with it, but every time I drive it, I long for the extra 200lb-ft of torque (at 3000rpm) and 200lb weight reduction (on front end) the LS3 was gonna provide... 2Js are heavy and 3.0L is not alot of engine to propel them smartly. Obviously boost helps; but not below ~3500rpm.

Just something to consider.

Also: it's easy to underestimate the time and cost associated with turbocharging; there are lots of "a few hundred here and a few hundred theres" that quickly add up to several thousand.
 

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I'd say I'm after a fair-weather sort of driver, hopefully lots of track days.
Sounds like fun! I'd get your chassis all squared away before going after more power.

I like the IS300 platfom, but have always found it feels a bit too heavy. That, combined with what "they" say about the 3SGE-powered Altezza always makes me yearn for a several hundred pound weight reduction. My turbo IS definitely feels like a heavier car than my stock daily driver IS; despite the turbo car having about 300 more rwhp.

Keep us apprised with your project!

Last: If you have an OEM header with cats that passes Cali smog - there is a pretty decent market around here for them. These cars are getting old, catalysts are wearing out and replacements are $$$
 
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