LC2nLS6

a Turbo Buick nut who dropped the compression to 8:1, swapped in a turbo cam and hung two 88 mm turbo's on it? I see lots of LSx cars running 6, 12, 15 psi but anyone running serious boost on a seriously well flowing LSx? I know boost isn't everything, flow is, but here me out...

I'm at least two years from my next Z06 purchase, so I was thinking what if-

Destroke the LS7, put in longer rods, drop the CR, and pump at least 25 psi of boost through it. Thinking it would shift at least at 7500 rpm. Pretty much a full on psycho street car that would start breaking things at will in the drivetrain whenever boost comes on. If the principles work for a little Buick V6, why not do it to the LS7? I think cam selection will be fun too. I have a little 210/210 on 110 billet roller in my Buick and it has no problem with 6400 rpm and over 500 to the wheels and it's almost half the displacement of the LS7. Just a thought...

paspar2

That's one thing I've never understood... People say it's cuz the Buick was built to be turbo'd but it still amazes me how a V6 can go to 25 psi on a consistent basis...

eviltwins

De-stroke it? Run a 210/210 cam? Twin 88's? None of this makes sense in the least, a 210/210 cam is going to nose off on a 427 by ~5000, tops.

There are people running serious boost into LSx motor, but the thing is with a big V8 with good flowing heads 25 psi on any turbo that can make it is going to be 1200++++ horsepower, and at that point most everything is a RACE CAR and people don't care about sharing dyno numbers at that point.

LC2nLS6

I said cam selection would be fun. Never said I'd put a 210/210 in there with two 88's. That was just a example of what a measly little Buick v6 can do. Peak hp on my 210 is right at 5200 but the hp graph is table top flat it only varied by like 40 hp from 4000-6400. Yeah, I'm thinking of a HP goal way north of 1200 hp, and it sure wouldn't be a dyno queen project either. It would have to rev to 7500 at least. Probably have to find some stage II Buick cam profiles and have a few custom grinds put together.

Yes, destroke it and drop the compression.

It would easily make 1200 hp on conservative boost levels.

Biggest questions are:

Will a forged bottom end on an LS7 even stand a chance and can the heads hold down 1500+ hp?

As long as there is no detonation it might have a chance.

nitrorocket

iTrader: (12)

Total apples to oranges. A buick head flows like crap, that's why they will take 25 psi. If you take a LS2 headed ls7 at 25 psi, you will be looking at damn near 50% more power per cubic inch at the same boost level.
A stock cube ls1 with ported heads makes about 900-1000 crank hp at 15 psi. What does a stock cube 231 with ported stock heads make at 15 psi????!!!! Throw a full blown race head (equal in port flow to an ls1 head) and that buick will not take 25 psi anymore without some bulletproofing. Just like an ls1.

Basically what I am trying to say, is like you said, FLOW. The crapier the head flow, the easier it is on the bottom end.

V8_DSM_V8again

A buick engine is also a long stroke motor that is why they got that much displacement from just 6 cylinders.

I got a better idea.

ETP heads on a iron block with a eagle crank (stock Ls1/2 stroke) and some mahle, diamond or wiesco turbo pistons and howards rods..

Or a World products warhawk block and head rig using all 6 available head bolts and the same reciprocating assembly (eagle crank etc) as the other engine.

I'd watch the bore size on any block.. The gasket can start to get too thin between the cylinders to withstand the cylinder pressure.

engineermike

It seems like it's time for a paradigm shift in our little performance world. There are mildly modified LT1's making 1000 rwhp at 22 psi, LS7's making 550 rwhp with a cam and headers only, 370 LS1's making 1000 rwhp through an auto, etc. . . the list goes on.

My point is, air flow is no longer as much of a limitation as it used to be. When all we had was L98 heads and TPI intakes, then airflow was how you made power. Now, I think we need to start looking more at engine management limitations and driveline components.

For instance, I have no doubt that you could put 25 psi boost on a stock LS7 and make 1500 hp. Fueling it properly might be more of a challenge, and building a car that can use 1500 hp even more of a challenge. 84 lb/hr injectors is about as big as you can go and still idle at over 1 ms pulsewidth. When you get over 100 lb/hr, the car will idle rich because you can't cut the pulsewidth any more. That sets the injector limitation at ~1300 hp, assuming you want it to idle good. And, of course, at those power levels, the stock PCM and MAF isn't going to cut it.

And putting 1500 hp in a street 'vette is all but pointless anyway. That belongs in a tube frame car that's capable of going in the 7's safely.

V8_DSM_V8again

Well I think the LS7 might need some forged pistons with a lower compression ratio to hit 1500 reliably.

The only time I have seen cast pistons live at that power level per piston is on 4cyls that have oil jets to cool the back of the piston..

I agree with the injector pulse width tech. I run 160's.. For an injector that huge they cycle pretty fast but you do have to raise the idle speed... I also run 85% alcohol fuel so I dont have to run them at as low of a duty cycle at idle as a gas engine due to AFR differences.

The LS7 is designed to be a potent naturally aspirated engine in stock form.

If you look at GMs forced induction northstar they reduced bore and have a supercharged 4.4 liter instead of a 4.6 like the NA models..

You can build a FI motor using LS7 components but would'nt start with a full new LS7 and work from there. If moving alot of air thru the engine using the turbo(s) is your priority I'd bolt the LS7 heads on a LS2 block. You will be less likely to have cyl head gaskets pop between the bores.

engineermike

Agreed. Also, don't forget that the Turbo Buick pistons are cast, albeit with steel internal support.

black_z

iTrader: (4)

There is a local 03 Cobra that is looking to make 1200-1300 at the wheels. Pure street car.

LC2nLS6

I figured virtually non-existant idling and 160# injectors from the start. Could scale down the boost levels to 5 psi and work up from there if it isn't fast enough. Still, a full on forged bottom end is necessary. So just pull the LS7 and save it, the trans and the rear end as a museum piece and start with a 6.0L, TH400, Ferd 9 inch combo. I like that idea.

If head flow isn't a problem, and we've got the other bases covered such as the bottom end, enough fuel, engine management (FAST etc...) and enough turbo, I still say destroke it and use longer rods and put a cam to take it to 7500 rpm. I saw another thread where a guy wanted to run a destroked 6.0L.

Then obviously the transmission needs serious attention. A built TH400 just sounds boring tho. Liberty? Gonna hate hacking up the car though with the cage and drivetrain fitment issues. Maybe I'll just scale all the way back to only a 6 psi boosted LS7 with LT's and a tune...

V8_DSM_V8again

I'd skip the TH400 and go to a 4L80E with a CM input shaft...

The 4l80e is a better platform than a Th400... Many parts between the two are the same but the input shaft is bigger on the 4l80e and parish here has snapped a stock 4l80E input at 1200hp or so.. Its either a built up 4l80e or a glide depending on if its going to be strip or street and strip.

Turbo2.4Liter

the buick 3.8 only has a 3.4" stroke