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408 Iron Block with what turbo??

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Old Aug 8, 2007 | 04:38 PM
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Default 408 Iron Block with what turbo??

I have finally decided on getting a built shortblock and after much deliberation, went with a 408. The shop where my car is at told me to go with a custom 72mm turbo, which was recommended by their turbo guru at Borg Warner. This is a 99.5% street car so they are going for quickest spool as possible. Doesn't this seem too small for this big of a motor? I don't want to have a turbo that spools up great, but then falls beyond its efficiency level in the upper rpm range. What do you guys think? Is this a little too small for a 408, or will this provide great spool as well as a strong upper end?
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Old Aug 8, 2007 | 04:40 PM
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72mm is way to small for a 408.

I wouldn't do anything smaller than a t6 flanges 88mm like the s88 or gt4788.

You need more than the 72mm can flow no to mention serious back pressure issues.
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Old Aug 8, 2007 | 04:41 PM
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s488 or s88 with a 1.10 t6 exhaust housing
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Old Aug 8, 2007 | 05:05 PM
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Originally Posted by cablebandit
s488 or s88 with a 1.10 t6 exhaust housing
yeah but when would the turbo spool up with that big of a turbo? Did I forget to mention this is a GTO (heavy as hell) with a 6-speed and a rear mount turbo? I need one that will spool up good in lower to mid range rpm, and still be able to breath up top.
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Old Aug 8, 2007 | 05:28 PM
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Originally Posted by geegro05
yeah but when would the turbo spool up with that big of a turbo? Did I forget to mention this is a GTO (heavy as hell) with a 6-speed and a rear mount turbo? I need one that will spool up good in lower to mid range rpm, and still be able to breath up top.
you might want to rethink your combo.

No one has tried to run that large a turbo in the rear of a street car.

a 76 will have issues feeding the car, i wouldn't want to think about a 72mm
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Old Aug 8, 2007 | 05:32 PM
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One of our S88's will make big power for you. Also we have a used one that has been turned in, freshened and is ready to go for a fraction of the price of a new one. Customer has now gone with one of our bigger series units that is due out in fall which he will be testing for us.
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Old Aug 8, 2007 | 06:03 PM
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I like my garrett gt-4508 81mm, ball bearing and makes boost as soon as you push the gas....it's almost like a nitrous car....and it's suppose to support 1250hp....just a thought....
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Old Aug 8, 2007 | 06:39 PM
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s85 with a t6 flange
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Old Aug 8, 2007 | 08:09 PM
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Originally Posted by red beast
I like my garrett gt-4508 81mm, ball bearing and makes boost as soon as you push the gas....it's almost like a nitrous car....and it's suppose to support 1250hp....just a thought....
Suppose to at high pressure ratios. An LS1 doesn't use high pressure ratios, and that 12 blade turbine wheel is horrible on exhaust flow. Flow just a touch more then a GT42 turbine wheel. I would have gone GT47-80R if you wanted 80mm BB and a garrett.
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Old Aug 8, 2007 | 08:44 PM
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Originally Posted by Alex @ CMS
you might want to rethink your combo.

No one has tried to run that large a turbo in the rear of a street car.

a 76 will have issues feeding the car, i wouldn't want to think about a 72mm
We ran a 76GTS outback on a camaro with a 408 low ci. It did spool late but that was expected for a larger outboard. However, on the customers previous 382, the 67mm did 708rwhp on 13.5psi . This new gts does 670rwhp on 11 or so psi.

For MAX spool on a rearmount car, do not use headers or cats. A shorty header at the most, use a smaller dia pipe depending on power level. a single 3" will flow great but take longer to fill up. Wrap the exhaust with heatwrap! we picked up alot of spool and it lost a bunch of heat from under the car.
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Old Aug 8, 2007 | 11:13 PM
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Originally Posted by Jake@EPP
We ran a 76GTS outback on a camaro with a 408 low ci. It did spool late but that was expected for a larger outboard. However, on the customers previous 382, the 67mm did 708rwhp on 13.5psi . This new gts does 670rwhp on 11 or so psi.

For MAX spool on a rearmount car, do not use headers or cats. A shorty header at the most, use a smaller dia pipe depending on power level. a single 3" will flow great but take longer to fill up. Wrap the exhaust with heatwrap! we picked up alot of spool and it lost a bunch of heat from under the car.
Cool setup,

as far as large turbo i ment a t6 flanged 88mm.

What happened to all those sts cars that got the MPS wheeled 67/76s?
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Old Aug 9, 2007 | 12:39 AM
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Originally Posted by DrTurbo
One of our S88's will make big power for you. Also we have a used one that has been turned in, freshened and is ready to go for a fraction of the price of a new one. Customer has now gone with one of our bigger series units that is due out in fall which he will be testing for us.
are those s88 t4 or t6? and what about the gt47-80r? t4 or t6?
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Old Aug 9, 2007 | 09:08 AM
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The S-series units are T6, the SX-series are T4 and T6. The GT47's are all T6 as well.
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Old Aug 9, 2007 | 10:00 AM
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Originally Posted by Jake@EPP
We ran a 76GTS outback on a camaro with a 408 low ci. It did spool late but that was expected for a larger outboard. However, on the customers previous 382, the 67mm did 708rwhp on 13.5psi . This new gts does 670rwhp on 11 or so psi.

For MAX spool on a rearmount car, do not use headers or cats. A shorty header at the most, use a smaller dia pipe depending on power level. a single 3" will flow great but take longer to fill up. Wrap the exhaust with heatwrap! we picked up alot of spool and it lost a bunch of heat from under the car.
Sorry for my lack of turbo knowledge, but what is meant by the outboard? I was hoping the 76 would spool great on a 408, so this outboard thing kinda confuses me Also, the cats were taken off like 2 years ago, we arn't running headers, and we have new stainless steel exhaust wrapped from the manifolds back and sprayed with that black stuff.
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Old Aug 9, 2007 | 10:10 AM
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Originally Posted by geegro05
Sorry for my lack of turbo knowledge, but what is meant by the outboard? I was hoping the 76 would spool great on a 408, so this outboard thing kinda confuses me Also, the cats were taken off like 2 years ago, we arn't running headers, and we have new stainless steel exhaust wrapped from the manifolds back and sprayed with that black stuff.
outboard like a boat engine....out back

Some STS kits dont seem to want to follow the rules while others make great power.

JDz28 made like 600+whp on a 347 and pump gas no meth.
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Old Aug 9, 2007 | 10:16 AM
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I will be running a 408 with a t6 76mm turbo, front mount of course. I will let you know how it goes. Motor should be here in 2 weeks or less.
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Old Aug 9, 2007 | 10:20 AM
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Thanks. haha let's just hope my setup follows the rules
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Old Aug 9, 2007 | 11:33 AM
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Originally Posted by markp03
I will be running a 408 with a t6 76mm turbo, front mount of course. I will let you know how it goes. Motor should be here in 2 weeks or less.


Let me quess..... a GT42-76mm Unit with a T6 Flange???

I bet shes's out of steam by 11-13 psi.....
Extreme back pressure with that turbo......

Kyle
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Old Aug 9, 2007 | 11:36 AM
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Originally Posted by NA$TY-TA
Let me quess..... a GT42-76mm Unit with a T6 Flange???

I bet shes's out of steam by 11-13 psi.....
Extreme back pressure with that turbo......

Kyle
I hope he's not. The GT42-76 will die out quick indeed.
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Old Aug 9, 2007 | 11:51 AM
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So I guess Jose talked with my shop and he recommended to them a TC76. That sounds a little better in my book. One question I have is what is the deal with the $100 race cover worth 75-100hp gains? Is this legit? Also, would it be worth it to get a ball bearing turbo?
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