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What flows better LS6 or 78mm Fast?

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Old 07-18-2009, 05:33 PM
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Default What flows better LS6 or 78mm Fast?

The title pretty much explains it self. If both manifold are un-touched which one would flow better. I know the LS6 works great, so would it even be worth going to a 78mm fast?
Old 07-18-2009, 05:38 PM
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I say no stay with the LS6
Old 07-18-2009, 06:54 PM
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Default Intake testing

It all depends on what your doing and running but check out these results
http://www.tpis.com/index.php?module=2_17_06

The Ls6 intake works great on many setup
Old 07-18-2009, 07:10 PM
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Originally Posted by khaotic
It all depends on what your doing and running but check out these results
http://www.tpis.com/index.php?module=2_17_06

The Ls6 intake works great on many setup

thanks for that link.
Old 07-18-2009, 08:36 PM
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I wouldn't upgrade to the FAST unless you are getting a used 90mm or the newer 92mm intake. Not worth the cost imo.
Old 07-18-2009, 09:00 PM
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Originally Posted by JScamaro
I wouldn't upgrade to the FAST unless you are getting a used 90mm or the newer 92mm intake. Not worth the cost imo.
Exactly. Stick with the LS6.
Old 07-19-2009, 01:42 PM
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how much is the 78mm? if its cheap enough to get for almost free after you sell the ls6 then I would
Old 07-19-2009, 01:42 PM
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yea ima stick with the ls6 and probably have tpis modify it to the oval port design. the link earlier in the thread shows some pretty good numbers for it.
Old 07-19-2009, 01:43 PM
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Originally Posted by thunderstruck507
how much is the 78mm? if its cheap enough to get for almost free after you sell the ls6 then I would
the last i seen its in the high 700 dollar range
Old 07-20-2009, 06:27 PM
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Got my 78 fast for $500 I think about 6 months ago.. no before #'s, but generally bolt on c5 z06's don't make 410whp/395rwtq on dynojets w/o even the help of a u/d pulley. (friend's car) and my car (02 SS 6spd with ls6 engine) makes 406rwhp/395rwtq with just bolt ons stock internal engine.

Again, no before and afters, but typically bolt on z06's make in the 370-385 area on this particular dyno jet, and I've seen at least 5 different c5 z06's run on it. So just by that info alone I'd say it's worth a solid 10-20whp over the ls6.

Or you could take the word for all these guys who have never seen one dyno or race or have ever owned one.

Personally, I'd go for the used 78 if the price is right, or a 90 if the price is right.. I was in the market for either one when I came across mine.
Old 07-20-2009, 06:46 PM
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if you haven't chosen to do anything yet I have a new in box fast 90mm intake that I'm not going to use anymore and trying to get $550+shipping for it (yes I know used ones are like 600, I'm just trying to get rid of it fast). There is a guy local to me that its pending to at the moment and I should receive a definate yes or no tomorrow.. after that I am going to post it here on ls1tech for sale if its a no.. if your interested

I think I remember reading somewhere that the 78mm does flow more than the ls6 like sombody above posted, I can't remember by how much though.
Old 07-20-2009, 09:09 PM
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Does anyone know what TPIS charges to modify the LS6 opening to a 90mm?
Old 07-21-2009, 11:05 AM
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Originally Posted by 1Bad00SS
Got my 78 fast for $500 I think about 6 months ago.. no before #'s, but generally bolt on c5 z06's don't make 410whp/395rwtq on dynojets w/o even the help of a u/d pulley. (friend's car) and my car (02 SS 6spd with ls6 engine) makes 406rwhp/395rwtq with just bolt ons stock internal engine.

Again, no before and afters, but typically bolt on z06's make in the 370-385 area on this particular dyno jet, and I've seen at least 5 different c5 z06's run on it. So just by that info alone I'd say it's worth a solid 10-20whp over the ls6.

Or you could take the word for all these guys who have never seen one dyno or race or have ever owned one.

Personally, I'd go for the used 78 if the price is right, or a 90 if the price is right.. I was in the market for either one when I came across mine.


You may just have a 'freak' car. I had a customer gain 4rwhp over an LS6 intake and was furious (not at me!)

I had an f-body with a crate LS6, UD pulley, LTs and ORY and FAST90 make 410rwhp 398rwtq on the dynojet 224 that I tune on. Additionally several years ago on a vette dyno day I had 2 C5Zs that were the same year (03) and both stock except for airfilters and one of them made 17 more than other one. If this were the case for your car as well...
Old 07-21-2009, 11:14 AM
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Ls6! FAST 78 waste of money!!!!
Old 07-21-2009, 06:14 PM
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Originally Posted by Frost
You may just have a 'freak' car. I had a customer gain 4rwhp over an LS6 intake and was furious (not at me!)

I had an f-body with a crate LS6, UD pulley, LTs and ORY and FAST90 make 410rwhp 398rwtq on the dynojet 224 that I tune on. Additionally several years ago on a vette dyno day I had 2 C5Zs that were the same year (03) and both stock except for airfilters and one of them made 17 more than other one. If this were the case for your car as well...
Yea mine made 410whp before, but when I switched to the drag radials it lost about 12whp from the previous dyno and I had it retuned to speed density and got it back to 406.



The car has always dyno'd high even bolt ons and turned the time at the track for me as well.. so you're probably right the car is just one of those cars, but I still believe the fast 78 is worth it in the $500 range used if you are getting rid of an ls6 intake for $300 at the same time. 4whp isn't worth it, but it could be more of a gain than that and especially with a cam or head swap.




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