"Fast" intake flexing - The 1947 - Present Chevrolet & GMC Truck Message Board Network

tucker69 · 03-21-2016, 10:58 AM

Does anyone have any knowledge/experience with the "Fast" LSXRT Intake flexing at the throat when the throttle is opened? i.e. as engine rpm rises the throat of the intake at the throttle body will push outwards. really freaked me out the first time I saw this. it just doent look right. I called "Fast" but didn't get much help. Thanks Casey

BR3W CITY · 03-21-2016, 02:12 PM

Like its physically deforming under load? Its a composite intake, but having enough flex to actually deform would throw me for a loop as well.

tucker69 · 03-21-2016, 05:37 PM

yes it is actually changing shape. I thought maybe I had a vacuum leak, I checked for that. has to be in the strength of the neck. as engine losses vacuum. however I would think it would pull in instead of pushing toward throttle body... Casey

BR3W CITY · 03-21-2016, 11:48 PM

Hmmm, we've got the regular non-truck version of the same intake on another car, and I don't recall ever seeing anything similar....now I wanna do stare at it and see if it actually does

izzy_Britton · 03-22-2016, 01:21 AM

Video please

Shon · 03-22-2016, 09:47 AM

that should not be happening.
Is it a New intake or a used one? if new, I would be calling Comp/FAST to figure out if they may some idea of what's happening, ie bad batch!?

tucker69 · 03-22-2016, 11:28 AM

Quote:

Originally Posted by izzy_Britton

Video please

You are asking a lot from a tech challenged ole guy. "Fast" asked for the same thing, I didn't have much luck...will try.. Casey

tucker69 · 03-23-2016, 12:34 PM

BR3W CITY · 03-23-2016, 05:57 PM

Check that your upper and lower shell pieces are fully seated and bolted together. The upper shell has the TB, and can move on its gasket.

homemade87 · 03-24-2016, 07:54 AM

Funny you are having this problem . When I was looking for a performance intake my tuner said stay away from the lsxrt truck intake . Said they flex to much and also is a tuners nightmare . That flex messes with the tune trying to nail down the little quirks . Apparently he has seen a few with the same problem . The intake is so large they just did not build enough support into it . Unless Fast did something to correct this problem it is just the nature of the beast .

tucker69 · 03-30-2016, 11:46 AM

Quote:

Originally Posted by homemade87

Funny you are having this problem . When I was looking for a performance intake my tuner said stay away from the lsxrt truck intake . Said they flex to much and also is a tuners nightmare . That flex messes with the tune trying to nail down the little quirks . Apparently he has seen a few with the same problem . The intake is so large they just did not build enough support into it . Unless Fast did something to correct this problem it is just the nature of the beast .

Got to love hotrodding.... $1000 intake that dances to the beat... why isn't that in the sales brochure?

akdg87 · 03-30-2016, 12:32 PM

this is a fairly good read on ls intakes: http://www.hotrod.com/features/1507-...ifolds-tested/

granted the factory intakes don't quite look as good as the aftermarket..

Robznob11 · 10-04-2020, 08:31 PM

So this is the only thread i can find on this but yea im freeked out to. Just put one on my truck and it does exactly what is stated above. I put a huge filter on and it lessened it some but definitely dances. Any update after 4 years?

03-21-2016, 10:58 AM	#1
tucker69 Registered User Join Date: Jun 2015 Location: shreveport, la. Posts: 160	"Fast" intake flexing Does anyone have any knowledge/experience with the "Fast" LSXRT Intake flexing at the throat when the throttle is opened? i.e. as engine rpm rises the throat of the intake at the throttle body will push outwards. really freaked me out the first time I saw this. it just doent look right. I called "Fast" but didn't get much help. Thanks Casey

03-21-2016, 02:12 PM	#2
BR3W CITY meowMEOWmeowMEOW Join Date: Sep 2009 Location: MKE WI Posts: 7,128	Re: "Fast" intake flexing Like its physically deforming under load? Its a composite intake, but having enough flex to actually deform would throw me for a loop as well. __________________ *'66 Short Step / SD Tuned / Big Cam LQ4 / Backhalfed /Built 4l80e / #REBUILDEVERYTHING* MY BUILD THE H8RDCPTR //\\ MY YOUTUBE CHANNEL REV J HD

03-21-2016, 05:37 PM	#3
tucker69 Registered User Join Date: Jun 2015 Location: shreveport, la. Posts: 160	Re: "Fast" intake flexing yes it is actually changing shape. I thought maybe I had a vacuum leak, I checked for that. has to be in the strength of the neck. as engine losses vacuum. however I would think it would pull in instead of pushing toward throttle body... Casey

03-21-2016, 11:48 PM	#4
BR3W CITY meowMEOWmeowMEOW Join Date: Sep 2009 Location: MKE WI Posts: 7,128	Re: "Fast" intake flexing Hmmm, we've got the regular non-truck version of the same intake on another car, and I don't recall ever seeing anything similar....now I wanna do stare at it and see if it actually does __________________ *'66 Short Step / SD Tuned / Big Cam LQ4 / Backhalfed /Built 4l80e / #REBUILDEVERYTHING* MY BUILD THE H8RDCPTR //\\ MY YOUTUBE CHANNEL REV J HD

03-22-2016, 01:21 AM	#5
izzy_Britton Registered User Join Date: Apr 2013 Location: Nor-Cal Posts: 632	Re: "Fast" intake flexing Video please __________________ WHO_DCTC - Wifes 05 Z-71 Build - Now defunct as she decided she wants an Escalade too Cream Puff - LS'd Square - Slow going on the back burner Tripple Threat - 3 Wrecks for the price of one build thread Project Delongdium - Step-Sons Plastic Clad 2003 Avalanche - DONE and Delivered.

03-22-2016, 09:47 AM	#6
Shon Registered User Join Date: Sep 2005 Location: sc Posts: 1,203	Re: "Fast" intake flexing that should not be happening. Is it a New intake or a used one? if new, I would be calling Comp/FAST to figure out if they may some idea of what's happening, ie bad batch!? __________________ 71 Cheyenne C10 LWB cam'd 6.0/T56 Swap

03-23-2016, 12:34 PM	#8
tucker69 Registered User Join Date: Jun 2015 Location: shreveport, la. Posts: 160	Re: "Fast" intake flexing

03-23-2016, 05:57 PM	#9
BR3W CITY meowMEOWmeowMEOW Join Date: Sep 2009 Location: MKE WI Posts: 7,128	Re: "Fast" intake flexing Check that your upper and lower shell pieces are fully seated and bolted together. The upper shell has the TB, and can move on its gasket. __________________ *'66 Short Step / SD Tuned / Big Cam LQ4 / Backhalfed /Built 4l80e / #REBUILDEVERYTHING* MY BUILD THE H8RDCPTR //\\ MY YOUTUBE CHANNEL REV J HD

03-24-2016, 07:54 AM	#10
homemade87 Registered User Join Date: Apr 2010 Location: Guntersville Alabama Posts: 1,073	Re: "Fast" intake flexing Funny you are having this problem . When I was looking for a performance intake my tuner said stay away from the lsxrt truck intake . Said they flex to much and also is a tuners nightmare . That flex messes with the tune trying to nail down the little quirks . Apparently he has seen a few with the same problem . The intake is so large they just did not build enough support into it . Unless Fast did something to correct this problem it is just the nature of the beast .

03-30-2016, 12:32 PM	#12
akdg87 Registered User Join Date: Sep 2013 Location: fairbanks, ak Posts: 339	Re: "Fast" intake flexing this is a fairly good read on ls intakes: http://www.hotrod.com/features/1507-...ifolds-tested/ granted the factory intakes don't quite look as good as the aftermarket.. __________________ build thread 1955 cameo turbo lsx 1993 K1500 Blazer 5.3/4L80e 2009 CTSV Sedan

10-04-2020, 08:31 PM	#13
Robznob11 Registered User Join Date: Feb 2004 Location: brownfield texas (west texas) Posts: 1,936	Re: "Fast" intake flexing So this is the only thread i can find on this but yea im freeked out to. Just put one on my truck and it does exactly what is stated above. I put a huge filter on and it lessened it some but definitely dances. Any update after 4 years? __________________ The Ghost 67 short wide full custom. 550 hp LSX, 4l80E, narrowed 9". Body dropped w/air ride! ........................ ___ .........________//__{\_____ ,,,,,,,/__(⊙)___//___/__(O)_/ @disciple2.rc 💪instagram💪 LED TAILS



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