I just bought a built Ls head!
- ported, polished and port matched.
- Crower 403 cams and valve train with new stock size valves
- Skunk2 intake manifold
- Blox 65mm throttle body
- STR fuel rail and fuel pressure regulator
- 440cc injectors
- I still have to get adjustable cam gears.

It will be going on a recently rebuilt '99 Ls block that is completely stock.
I have a 4-2-1 header, hi flo cat, and full 2.25" exhaust.

I have 3 questions...
1. Will my fresh, but stock bottom end be reliable with this head and a good tune?
2. What else, besides forced induction, would you recommend that I do next to get even more out of this set up.
3. How many HP do you think I'll get out of this head?

i mean you really wont gain that much power without a tune...but on a stock bottom end maybe like 155whp

the set up will be fine as long as it was built right and that you are not zipping around town at 9,000 RPM the rod bolts wont hold up and i agree with interaguy about 150-155 whp and that is a generous number if your not FI the car beef up the bottom end with jdm p30 pistons slap it all together with a gsr trans with a 4.7/4.9 final drive and u got a nice street motor

Actually, I do have plans to add P30's and ARP rod bolts, eventually and trade my tranny for a B16 tranny.
I do drive pretty hard, some times, and just want to know that the stock bottom end can handle this head, until I can build a bottom end.

the motor can handle it no problem...one word of advice is if you plan on bringing the motor past 8K and driving it hard a decent amount...every once in a while check the valve adjustment b/c with the nonvtec valvetrain how its setup, they can start to come out of spec if the motor is rev'ed up higher than normal

I am making 133 whp with just IHE and tune. You should see 150-160 at the wheels with a good tune. Your bottom end will be just fine for the head set up.

So, is that even with my new Crower double springs and retainers?

not a fan of port and polish ..unless it's strictly on a track .. desposites will cling worse then before

dual springs and retainers will help a ton

If you maintain you car correctly and regularly you should not get much build up in the head and CC. Fuel treatments and top end engine cleaning every 30K goes a long way to keeping the engine free from carbon build up. I would go ahead and do the ARP rod bolts and P30 pistons now while the motor is out of the car as it sound like it is. B18b and B20 rod bolts are very week and cant handle revs past 7500. I have ARP rod bolts in my B18b, very easy to do.