FAST versus LS6 Intake with 408

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Feb 5, 2008 | 07:59 PM

Steve Bryant

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From: Wichita, Ks

FAST versus LS6 Intake with 408

I've been trying to find a dyno comparison of the differences between a FAST (78 or 90 mm) and an LS6 manifold with a 408 CID engine and a moderate cam (let's say durations of 224/224 or less). I've done many searches, to no avail. Can anyone point me to some hard data?

Thanks,

Steve

Feb 5, 2008 | 08:16 PM

Tony Mamo @ AFR

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Your gains will be largely dependent on how effective your cylinder heads are....not so dependant on displacement. The more kick *** your heads are the larger the gains with a stock (or ported) FAST because your LS6 intake will appear as a larger restriction in the pipeline.

Dont think if you find a 408 that swapped and say picked up 20 RWHP that your guaranteed to do the same....its not the case.

Just an FYI....

Tony

Feb 6, 2008 | 10:42 AM

Steve Bryant

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From: Wichita, Ks

Tony,
Thanks for your input. Yes, I understand that the induction system as a whole can only be as efficient as (or is limited by) it's weakest link.

Steve

Feb 7, 2008 | 09:24 AM

Steve Bryant

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From: Wichita, Ks

I just want to give this thread a bump. Does anyone have a comparison between these two manifolds on a stroker engine? A while back, I put together a pretty comprehensive comparison of the various manifolds here http://www.performancetrucks.net/for...d.php?t=392089, but these were all based on a 5.7 L LS1. I'd like to see what happens on a bigger displacement engine, not just supposition.

Thanks,

Steve

Last edited by Steve Bryant; Feb 9, 2008 at 10:07 PM.

Feb 7, 2008 | 12:01 PM

2000 Tran Zam

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From: Ahwatukee, Az

Im not sure what your goals are with the setup, but that 224 cam is TINY in a 408. in my 408 I was running a 236/230 cam and thats with forced induction and 13 lbs of boost.

Might wanna go with a lil bigger cam especially if your looking at differences between a fast and ls6 intake. just my opinion.

Feb 7, 2008 | 12:12 PM

CALL911

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From: IN

For that cam, with your combo, I doubt spending the extra $ on a FAST will be worth it, as you shouldn't really see that large of gains over the LS6 intake.

Now, if you had a much larger cam, and a killer breathing set of heads, then you would gain much more with the FAST intake.

In short, the most gain you'll probably see will be 3-5 RWHP (max). But, if setting ideal conditions up with a larger cam that needs more air with a big set of heads, you might see up to 15 RWHP (max).

Feb 7, 2008 | 12:24 PM

SSwt00SS

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From: Dallas, TX

i can help you somewhat but its an Ls1 not a 408...

here are my dyno numbers for the following setup (May 2007)...409/386

SLP Lid
SLP Bellow
Ls6 intake
Comp 224/224 .581/.581 @ 112 Lsa
Patriot Ls6 "Style" Stage II heads (59cc) 6.0L castings
Ls6 Oil Pump (ported/shimmed)
Ls2 Timing Chain
LT's/ORY w/SLP LM cat-back
HP Tune

VIDEO from RPM (Jan 2007), head install...
http://www.youtube.com/watch?v=4aAH7zkJAl0

VIDEO LG Dyno Day (May 2007):
http://www.youtube.com/watch?v=z9lzXmf7H3Q

Gains after swapping out the Ls6 intake for a lightly ported FAST 90/90 and retune ONLY. the reason I am showing you (2) dyno sheets is because RPM did the retune and since I could not find my dyno sheet from RPM showing 409/388, i wanted to show what my car made from the LG dyno day May 5th, 2007 for comparison purposes and to show that coming with 5rwhp/rwtq means the number are not BS. Infact, if you look at the date and times on the dyno sheets, the time difference was me driving from one shop to the other...

VIDEO:
http://www.youtube.com/watch?v=Fhl_z0pWg6Q