LS7 Intake under boost
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Staging Lane
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From: KS
LS7 Intake under boost Well my build has changed today to a single turbo setup, either 76 or 88 depending, and the basics will be the LSX block, LS7 heads and an LS7 intake...does anyone have an idea at what power the LS7 intake starts to fade? I plan around 750rwhp on pump gas, then the occassional big boost 1000+ rwhp for the track with race gas. Is the LS7 intake good to go up to that boost? Or should I start thinking Hogans? 
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Originally Posted by Got Me SOM
I dont think 750 on pump gas is realistic.
Thread Starter
Staging Lane
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From: KS
There is a local guy that has a GTO, stock bottom end, stock ported heads, stock intake making 650rwhp on 5psi with a T76...how is 750 not possible? The turbo is good to 1000hp. I might go with the 88...but that's another $1500 basically for the turbo alone.
Good to know the LS7 intake is fine up to 1000hp, I figured it would be, just wondering what's been done on it so far. LS7 heads and intake it is then!
Good to know the LS7 intake is fine up to 1000hp, I figured it would be, just wondering what's been done on it so far. LS7 heads and intake it is then!
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Originally Posted by blown4now
The turbo is good to 1000hp. I might go with the 88...but that's another $1500 basically for the turbo alone.
Or. . . if you want to optimize power on the 76, you could built a small displacement engine using the LS7 heads/intake. You could use the 4.125" LS7 block with a 4.8 crank, for 350 cid on the nose. Or, even better would be a 6.0 block with the 4" bore and the 4.8 crank, for 329 cid. That is, if the LS7 heads work on a 4" bore. That would give you very good cylinder filling and a good backpressure ratio on the turbocharger. You could cam it however you want and rev the pee out of it.
Mike
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Staging Lane
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From: KS
I was thinking LSX block with a 4.125 bore for the LS7 heads and a stock stroke Callies crank, or possibly even go with a 4" stroke and use the T-88 turbo. Thats if it's possible to keep that motor around 8.5:1 compression and keep the wrist pin away from the ring lands. Have to see. So many dang questions!
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Originally Posted by blown4now
I was thinking LSX block with a 4.125 bore for the LS7 heads and a stock stroke Callies crank, or possibly even go with a 4" stroke
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Originally Posted by engineermike
When the LS7 stuff is making 500 - 550 rwhp on motor alone, I bet you could get over 900 rwhp on pump gas. That is, of course, with the right turbo. The 76 isn't going to cut it. Heck, with my LTx, I'm making 700 rwhp through an auto/loose converter at only 17 psi.
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Staging Lane
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From: KS
Originally Posted by engineermike
So you're talkin' 388 - 427 cid range. The T88 will actually start to see some problems with a motor that size flowing that well. You might consider the S88 from forcedinductions.
Wish you lived in KC so we could enjoy a brew and talk! 
Originally Posted by blown4now
There is a local guy that has a GTO, stock bottom end, stock ported heads, stock intake making 650rwhp on 5psi with a T76...how is 750 not possible? The turbo is good to 1000hp.
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Staging Lane
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From: KS
I understand that his GTO may not be the same as all, and I'm not sure why it makes so much power. And I also know that you can't just go buy a turbo cause it says it's good to xxxxhp and plan to get xxxxhp out of it. I was simply stating that, for basics, the T-76 is supposed to be good to 1000hp on a engine around the cubes i'm building. I understand there are a lot more technicalities to look at, but just a general statement is all I was making.
Then let me ask you all this: Let's say with a 4.125 bore, 4.00 crank, LS7 heads and intake, which turbo would YOU put on there? I would like to stick with an air to air intercooler, but most I'm finding are only 1000hp cores. Are there any air to air that will support, say 1200hp? Or should I start looking at....*sigh*....water to air.
Then let me ask you all this: Let's say with a 4.125 bore, 4.00 crank, LS7 heads and intake, which turbo would YOU put on there? I would like to stick with an air to air intercooler, but most I'm finding are only 1000hp cores. Are there any air to air that will support, say 1200hp? Or should I start looking at....*sigh*....water to air.
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Originally Posted by Got Me SOM
you make 700 on pump gas?
Mike
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Originally Posted by blown4now
Can you expand on that?
Compressor: All turbocharger compressors are more efficient at high flow rates and high pressure ratio's (boost). At 850 fwhp on an LS7, you're only talking about 6 or 7 psi, or a pressure ratio of 1.5. So, even though a T88 may be rated for 1250 hp, its not that efficient at 850 hp and 1.5 Pr. So, in order to get good low-boost numbers on a large displacement, well-flowing engine, you have to size the turbo bigger than what you want. Just for example, a T76 would be only 50% efficient at the same level.
Turbine: Again, the cid and flow make this more difficult than most. You will definitely need a T6 exhaust side. That's why I recommeded the new S series of turbochargers. They are available from S76 up to S88, all with a T6 exhaust side. However, the S88 will support 1500 hp and is about the same size as a GT42 and much smaller than the large-frame T91 that's only good for an extra 50 hp.
Don't take this from me, though, on a serious build like this. Call Jose at forcedinductions.com. He has alot more experience than I do.
Mike
Last edited by engineermike; Apr 2, 2007 at 06:08 AM.
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Originally Posted by blown4now
Then let me ask you all this: Let's say with a 4.125 bore, 4.00 crank, LS7 heads and intake, which turbo would YOU put on there?
Keep in mind that this combo has some serious parts and will make well over 1000 rwhp on race gas.
Mike
