Keep the FAST 90 for boost?
Thread Starter
Burning Brakes
Joined: May 2011
Posts: 1,216
Likes: 56
From: Houston Texas
Keep the FAST 90 for boost?
About to kick off a 408TT build, and deciding what to keep...
Have heard/read of these not doing so well under boost. Looking for opinions here, and if the manifold should get the boot then what manifold would be recommended? Don't particularly want to run an oem ls2 manifold since they really don't flow well at all.
Planning on boosting to 20psi
Have heard/read of these not doing so well under boost. Looking for opinions here, and if the manifold should get the boot then what manifold would be recommended? Don't particularly want to run an oem ls2 manifold since they really don't flow well at all.
Planning on boosting to 20psi
Le Mans Master
Joined: Jan 2009
Posts: 7,767
Likes: 19
From: East Texas
Arun set the record on a stock ls6 went like 8s @ 160mph in the 1/4 i'm running a stock ls6 too @ 16+ boost car is in the 9s, I would sell the fast for the $ and get a ls6 but that's just my opinion. I'm not a expert maybe Arun will help or Brett blown blue. good luck brother
Last edited by a/c man; Sep 26, 2012 at 08:53 PM.
Tech Contributor
Joined: Apr 2007
Posts: 10,924
Likes: 78
From: Forney Texas
I would only use the FAST 90 if you think it looks good as a paper weight. Yes people have gotten away with running them and you might too, but what if you're one of the ones that don't get away with it? They no longer support the 90, so if you kill it, you're not buying a new replacement lower to fix it. It's not even remotely necessary to make good power. Trade it out with a LS intake owner with some cash on top is my recommendation.
LS2 doesn't flow well? How well does it flow @ 20PSI?
I'll give you a hint: I made 1021RWHP with a 403 using a LS2 intake.
Everything changes with boost my friend. Boost is the great equalizer
LS2 doesn't flow well? How well does it flow @ 20PSI?
I'll give you a hint: I made 1021RWHP with a 403 using a LS2 intake.
Everything changes with boost my friend. Boost is the great equalizer
Last edited by BLOWNBLUEZ06; Sep 27, 2012 at 12:11 PM.
Former Vendor
Joined: Jul 2010
Posts: 4,504
Likes: 4
From: Waterloo Ontario
FAST 90 has gotten a bad rap, but it does work.
If your going to use it with boost-silicone it together with the supplied gasket.
FWIW-I am currently using a 102 on my car and my friend Frank is using a 102 on his 402/F1R combo.
He just came back from Georgia and ran a 171mph on street tires and was pretty happy for his first time out and how the car performed.
If your going to use it with boost-silicone it together with the supplied gasket.
FWIW-I am currently using a 102 on my car and my friend Frank is using a 102 on his 402/F1R combo.
He just came back from Georgia and ran a 171mph on street tires and was pretty happy for his first time out and how the car performed.
Le Mans Master
Joined: Jul 2005
Posts: 7,121
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From: Shreveport/Bossier Louisiana
St. Jude Donor '08
I really want the Fast 92 so I don't have to mod anything for it to fit. I've read many times that the 92/102 are far superior to the old 90mm intakes as far as strength is concerned.
Tech Contributor
Joined: Apr 2007
Posts: 10,924
Likes: 78
From: Forney Texas
Hey Arun, I just wanted to mention that the two I've personally seen fail were split across the valley side-to-side and in the back. Silicone wouldn't have saved these. I've received calls from other forum members with the same issues. I would certainly be less reluctant to use the new 92 or 102 models if they're made of different or stouter material.
Le Mans Master
Joined: Jul 2005
Posts: 7,121
Likes: 3
From: Shreveport/Bossier Louisiana
St. Jude Donor '08
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Former Vendor
Joined: Jul 2010
Posts: 4,504
Likes: 4
From: Waterloo Ontario
Hey Arun, I just wanted to mention that the two I've personally seen fail were split across the valley side-to-side and in the back. Silicone wouldn't have saved these. I've received calls from other forum members with the same issues. I would certainly be less reluctant to use the new 92 or 102 models if they're made of different or stouter material.
The 102 is supposed be much stronger-so we'll see. I will make a call to comp to confirm if the newly released 92's are the same material as the 102's.
From all the folks I have talked to who went from the Fast to a LS2-said they noticed a difference-but not in a good way.
Thread Starter
Burning Brakes
Joined: May 2011
Posts: 1,216
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From: Houston Texas
Haha, a lot of conversation on here! Thanks all for the feedback!
Only 1,021rwhp?? My neighbor's Honda makes that with 12 bottles of NOS... haha
Seriously though, that's some awesome power! 
I'm certainly with you that boost can make up for some flow restrictions, but an engine is still in all simplicity just a pump. I tuned a friends C6 with patiot 2015 heads, 225/229 cam, and lg's with his LS2 manifold and then a while later when he upgraded to a FAST 102. Went from 427whp to 465whp, with just the manifold change and I even had to pull 3deg timing out up top because of the FAST. Obviously the LS2 is capable of flowing, like yours feeding air for over 1k whp, but there is definitely going to be a greater pressure differential across that manifold compared to some of the better ones out there.
Judging by all the comments, I think the safe play here is to sell off the 90.
Aligns with the assumption I would have made. Guess I have to decide back to a ls6 manifold with smaller throttle, or find a 102 
.
What about the ls3 manifold if switched to rectangular port heads?
Only 1,021rwhp?? My neighbor's Honda makes that with 12 bottles of NOS... haha
Seriously though, that's some awesome power! I'm certainly with you that boost can make up for some flow restrictions, but an engine is still in all simplicity just a pump. I tuned a friends C6 with patiot 2015 heads, 225/229 cam, and lg's with his LS2 manifold and then a while later when he upgraded to a FAST 102. Went from 427whp to 465whp, with just the manifold change and I even had to pull 3deg timing out up top because of the FAST. Obviously the LS2 is capable of flowing, like yours feeding air for over 1k whp, but there is definitely going to be a greater pressure differential across that manifold compared to some of the better ones out there.
Judging by all the comments, I think the safe play here is to sell off the 90.
.What about the ls3 manifold if switched to rectangular port heads?
Last edited by JDS99; Sep 28, 2012 at 12:45 AM.
Drifting
Joined: Feb 2006
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From: New Hartford IA
I think the biggest problem under boost is the bottom since it has a lot of flat area and not ribbed/reinforced. I bet if one were to add some padding to the valley area that fully supported the base it would not be as big of a problem.
Drifting
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Melting Slicks
Joined: Jul 2008
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From: Houston Texas
2018 Corvette of Year Finalist
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Were they tested at that pressure with the intake heated to engine temp, how many times was it cycled from boost to vacuum and back at operating temp, how many heat cycles, etc. There is a big difference between one burst at 35psi and an actual durability test.
Drifting
Joined: Oct 2004
Posts: 1,621
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Good point, I told them what I was using and they said no worries.
