what do I need to get to 400 hp.

[Naaman]

You can definitely pick up some power with a simple tune, even on a stock engine, and still keep the tune very safe.

Since these tunes "stock" will command 11.5-11.7 AFR, they don't make the HP they could, and that's extremely rich for a naturally aspirated engine. That's more like an AFR you would see when running a power adder.

Even if you just leaned out that WOT AFR to about 12.5 you are going to pickup probably 10-15 HP and still be extremely safe.

If you want to push it and lean it out to 13.0-13.3 you could see 20 HP but that's on the ragged edge of safe.

On timing it depends on the year of the LS engine you're dealing with as to how much you can get away with, because they changed cam profiles and cylinder head designs throughout the LS1 production run.

Usually the older 98-00 models like 26 and even 28 degrees at WOT for best power, while the 01-02 models tend to like 23-25 degrees. The LS6 engines also don't need as much ignition lead to make power either.

My 00 SS for example with it's original heads, but running a custom smallish Vinci cam, only likes about 25-26 total timing at WOT with 94 octane. When I moved out west and had to feed it a diet of 91, it had detonation issues right away, and was pulling 4 degrees out of it (the most it will pull as that's where I have it set)
I had to go in and log, and retune the entire timing table map and found the engine just didn't like anymore than 21-22 degrees total timing at WOT on this cat pee we have for gas out here. It now runs pretty clean throughout a pull, and on the hottest days you might only see 1 degree of timing pulled in just a hand full of various timing blocks. That's not enough to worry about. As ambient temps cool off it goes away completely.
With that said, you can see why I prefer to have my AFR's a little richer. I tune this car with a pretty steady 12.6 AFR at WOT to help with the detonation. It's a tad rich, and I could go leaner and make a little more HP but at the risk of more detonation. I'd rather play it safe. Never know when you might get a bad tank of gas too, and that's another reason to have a richer AFR.

That's another subject, since we have ethanol blend fuels. Supposed to be 10% but I've seen 17% mixed in some stations, it's not regulated very well.
10% ethanol has a 14:1 stoich, while real gas is the normal 14.7:1 we are used to hearing about. So with ethanol mixed gasoline, you should be tuning for a richer AFR anyway to compensate. Approximately .7 difference in AFR's. Trying to run 14.7:1 stoich with 10% ethanol fuel is running the engine a little lean.

It's funny: I can talk engine theory all day long and know enough to "understand" what's going on here... but time and again I'm humbled to learn how much I don't know. :P

FBJ, what is your opinion on octane boosters? Forget about dollar/performance ratio. I'm just wondering, theoretically, do they actually do what they claim? If I'm "safer" on 93 octane, but I can only get 91, is the octane booster going to do anything for me?

[Firebirdjones]

I'll admit I haven't used them in years, but used to try different brands all the time years back. Never noticed anything at all. Don't believe it hurts anything but never found them to help anything either.

There have been several new ones that hit the market since I've experimented with them so maybe something out there works, I just haven't had the desire to try any of them.

I always had better results stopping at stations that had 100 octane or 110 octane and just pumping in a couple gallons to mix with the 91-93 stuff. Used to be higher end gas stations throughout town that carried this in unleaded form. Unfortunately you can't find that easily anymore either.

[Whamhammer]

It's funny: I can talk engine theory all day long and know enough to "understand" what's going on here... but time and again I'm humbled to learn how much I don't know. :P

FBJ, what is your opinion on octane boosters? Forget about dollar/performance ratio. I'm just wondering, theoretically, do they actually do what they claim? If I'm "safer" on 93 octane, but I can only get 91, is the octane booster going to do anything for me?

I remember a High Tech GM Performance magazine article from the late nineties that examined octane boosters, they determined that most only raised the octane level by a point or so, some actually lowered the octane rating. I might be able to dig it up and scan it, I think it was the same one as the article where they examined the LS1, as fitted for F bodies (ca 1997)?

[SMWS6TA]

RACE GAS | Racing Fuel Concentrate

Here you go is you want real octane boost