IMO, Lee is right on!!! Take that 14g's and push some serious hp out of what you've got. Or......buy a new '07.

 

Thanks Lee.....that's what I needed from all of you....some good common sense advice.....and I got it!!!
After careful consideration....I think I will stay put with what I have right now....maybe in the future I'll consider making additional power modifications.......but for now......I better give my bank account a rest! .......for now

Thank you all for your input....it is much appreciated!

 

[sm=icon_rock.gif]

 

A 346 ci engine is more than enough displacement to get 700+ rwhp reliably. This is with turbocharging not naturally aspirated of course. I say turbocharging and not forced induction in general because for the same boost level a turbocharged engine will make more horsepower than a supercharged engine. The problem is, however, the LS1 wasn't specifically designed for running a serious turbo (or supercharger) setup. To do it "right" you need to lower the static compression ratio to about 8:1, use forged internals, ceramic coat the exhaust ports, and use sodium-filled exhaust valves. Obviously it is easier to get hp out of a 427, but 5.7 liters is not small by any stretch of the imagination. If you don't want to use a turbocharger or supercharger to get high horsepower then a larger displacement engine is the definitely way to go.

 

I was talking with a bud of mine and he suggested twin turbos on my 454. 9.5:1 comp, and forged internals,
rated at 400 hp now.
Opinions anyone?

 

That's a bit more compression than is ideal for a turbo setup. But that just means you can't run as much boost. You will still have the low-end grunt with the benefit of higher horsepower. If you really wanted to max out the horsepower, you would have to lower the compression. But we're talking a 454 here and even running mild boost (~10 psi) you'll have more horsepower than you'll know what to do with. You could always lower the compression a tad with different heads that have a larger combustion chamber.

 

I'm letting my ignorance hang out here, I don't really understand the relationship between the boost and the compression. I just figured that the turbos mean you can pack more into the cylinder. I'd like to get straightened out on this, so let 'er rip.

 

this is long but worth saying.

A 346 cubic inch engine is capable of producing 700+ HP - correct. But a stock LS1 (346 cubes) or LS2 (366) engine cannot - not for long anyway. I have not seen a durable turbo, SCr, or NOS application on a stock LS1 or LS2 block at over 550 RWHP. By durable I mean one that will last at least two years when the HP is used occasionally, say about as often as you would if you ran five runs at the drags once a month and exercised it on the street for a second or two once in a while.

And I have seen "heavily used" turbo and SCR stock blocks bite the dust with a bit less than 500 RWHP - at least four, with a variety of problems, a bent crank and rods (not sure which happened first), a cracked piston, and cracked blocks.

A strong aftermarket short block is not that costly: the one in our Camaro cost about $3700, is 408 cubic inches, and just bulletproof as an LS series engine will come. You can order it your way, including the compression ratio lower for your planned boost (8.5 or 9:1 wqorks well) or a compromise (my vette is only 10:1, so it can take about 9 lbs), or astronomical if you are not planning boost (the Camaro is 11.62:1, a good NOS ratio), and with the pushrod clearance cut out for extreme rocker angles, etc.

Before getting into my own rules of thumb, it is worth remembering that it is the torque that destroys the engine (twists it apart) and not strictly speaking HP. Suppose we set an upper limit of 525 RWT for a LS1 (I would never go higher): 525 ft lbs at 5000 RMP is 500 HP, but at 6500 it is 650. Basically, by choosing the right cam, you can move the torque peak around the RPM range. So you can actually gain a good deal of HP while still staying durable (sort of durable, anyway) but making it a high-reving engine: pick a cam that pushes the torque peak up to the red line. Just realize that pushing the torque peak up to 6500 means the engine idles and drives around town like a sick pig.
that said, my own rules of thumb are:
- stock botom end is good for about 475 RWT (if abused) and about 525 (if not)
- the stock aluminum block and heads are a good basis up to about 650 RWT
- use an iron block above that or go to a C5R or LS7 block if you have the money and need the light weight.
- at somewhere south of 1000 RW the stock heads are too weak even if re-worked - need AFR or other heavy deck heads, and O-ring gaskets (getting expensive now)
- at around 1300 RWHP the LS engine just is out of its range, it does not have enough head bolts and strength. Its time to go aftermarket everything.

A really good turbo or SCr application should have the compression ratio lowered: my C5R is a compromise with 10:1, but ideally 9:1 or 8.5:1 for heavy boost applications. The problem with lower compression is that you don't get much power without the boost, and as a result, driveability (a sharpness in resonse) and economy suffer. That's not important in a racing engine but I picked 10:1 as the lowest I would go, even though I knew it limits me to about 8-9 lbs of efdfective boost, because the engine has plenty of power and driveability around time without ever getting into the boost. A rough rule of thumb is about 25 RWHP per lb of boost which means 7 lbs on a stock LS6 (350 RWHP stock plus 175) is about at the limit.

All in all, you can buy complete engines from various aftermarket companies with everything built to last and work well together, including tubos, etc.

That';s really the way to go unless, like me, you just love to engineer it yourself more than even drive the beast.

 

A cylinder can only handle so much pressure. So an engine with a higher static compression ratio can handle less boost than an engine with a lower static compression ratio. Lower compression engines under high boost stay near peak cylinder pressure for a longer time (more crankshaft degrees) than a higher compression engine under low boost. The final compression may be equal but the lower compression engine will have a higher "overall" cylinder pressure. The longer the pressure is maintained, the more hp is developed.

Also, if you let the turbo do more of the compressing (and then run it through an intercooler), the final amount of heat generated after it is compressed will be less than if the piston was allowed to do more of the compressing. So actually, you can have an even a higher final pressure with the lower compression/high boost setup vs. the higher compression lower boost setup.

 

No doubt people can figure I I love this stuff: I used to design these things for a living.

I view it a bit differently than the cylinder only handling so much pressure. The basic LS engines can take only so much cylinder pressure, but a rebuilt one can take much more, yet there are still limits to a combination of high compression and high boost.

When you get down to it, an amount of power, say 650 HP at 5000 RPM, will take the same amount of cylinder pressure upon combustion regardless of how the power is made: turbo on non-turbo, high or low compression, etc. Once rebuilt, the LS engine can take boost up to about 28 lbs at 8:1, or 1300 HP.

The real issue with high compression and high boost has to do with the speed of combustion inside the cylinder and the pre-disposition of the fuel-air mixture in the cylinder to pre-ignite (i.e., explode when it wants to, not when you want it to). When things work like they should, a lot of air-fuel mixture makes its way into the cylinder and then explodes when the spark tells it to. The explosion may look and feel instantaneous to the naked eye, but it actually takes a split second, about 1/3000 of a second, to move outward in a wave of flame from the spark plug down through the cylinder. As it do4es it produces a steady pressure, for the entire power cycle, on the top of the piston: torque. And the more air and fuel you can cram into the cylinder, the bigger the bang and the more pressure and the more torque and the more HP.

But air-fuel can misbehave. If you boost too much air into a cylinder (high boost) and then "squish" it too fast (high compression), it does not explode outward from the spark plug in 1/3000oth second, but instead all of it explodes simultaneously througout the cylinder in 1/50000th second. This is detonation, or pinging, or knock. It produces next to no power (there is no wave of steaqdy pressure and torque) and will, sometimes, blow a motor apart (the sharp bang caves in the top of the piston).

You can avoid this only through any of four methods (unless you can re-design the basic engine, then you have other choices, too).

First, you can adjust the timing, firing the mixture before it explodes itself, but to do this effectively you have to advance the timing so early (before the mixture detonates, as to where you get little power: this is self defeating, and sometimes does not work at all.

Second, you can use higher octane fuel, which won't detonate until a higher temperature-pressure level. This is why people use race gas in really hi-po cars: its higher octane permits more compression ratio or more boost or both, hence more power (the gas itself produces no more power unless you do one or both).

Or, you can push less air into the cylinder (lower boost) and still have your high compression.

Or, you can lower the compression ratio and go ahead and cram more air with with the SCr high boost. If you do this last approachr, you get about half what you give up: lowering compression ratio cuts power but it permits more boost -- enough to more than make up for what you lost. So, an engine with say, 6:1 compression ratio can take gobs of boost (50 lbs) whereas one with 11:1 can take only five.

It is always a compromise. High compression means high efficincy: good economy. But it limits the boost you can get. My compromise was the following. I built my C5R with 10:1 compression ratio, giving up a bit of around town fuel economy (about 2 mpg) but with a target of one thing: at 10:1, my engine can take enough extra boost that no stock, LS7 C6, with its 11.5:1 ratio, would be able to SC enough boost and beat it in RWHP or the 1/4 mile: the LS7 stock compresison ratio does not permit enough boost. An LS7 will have to be rebuilt - rather a costly effort, to match or beat me. A rather childish goal, perhaps, but that's why I did it.