85mm LS6 Intake Question
85mm LS6 Intake Question Hi found a good deal on a LS6 intake so I bought it. My plans are to open the mouth of the intake to 85mm's to match my 85mm TB but after seeing a few pics since I don't have it yet these intakes don't have alot of material after the 78mm opening. I saw a thread where one guy opened one up to 87mm and I have seen it done to the FAST 78mm intakes so my question is has anyone else tried this mod if so could you shed some more info and maybe pics? I'm asking because I would rather sell it and try to find a FAST 78 at a good price(which was my original plan) since it has been documented than ruin a LS6 intake.
Here's the 87mm LS6 Intake Thread hopefully this guy will chime in:
https://ls1tech.com/forums/generatio...s6-intake.html
Here's the 87mm LS6 Intake Thread hopefully this guy will chime in:
https://ls1tech.com/forums/generatio...s6-intake.html
My original plan was to buy a FAST 78 but I got a deal on a LS6 that I couldn't pass up so I bought it and I see that people are getting good results from the TPIS 90mm LS6 so if I could modify the opening of my LS6 to 85mm to match my 85mm TB i'm thinking I could see simular results.
So, do it. My testing has shown that the LS6 runner air speed doesn't increase to the point of where there is a diminishing pressure change until somewhere around 430 ish g/s (measured @ the MAF so divide by 2.5 for individual runner flow). For this reason, I have always suggested that mild cam guys not port the runners. Every test made by shops & members have shown benefits by increasing the inlet size on the LS6 intake. Even just going to an 85mm TB without opening the inlet will help. It's also very important that you have the MAF table rescaled after the modification.
Actually an LS6 intake was not the intake I wanted unless I got one at a really good price(which I did) because I had a ported wieand with a fully modified 85mm opening on my car that I just sold and since the two are so close besides the LS6 being about 20lbs lighter I really wanted to try out a Fast 78(modified to 85mm) because of the lightweight and ability to port but because of the great deal I got on this LS6 and a Thread in the dyno section that showed a LS6 vs 96mm Aluminum PP vs FAST 92 the LS6 made more torque and only a few less horsepower than the 96mm aluminum PP intake with a stock ported TB I could be wrong but I think with a bigger TB the LS6 would be close to the FAST. I just recieved My LS6 today and after bolting up the TB there is ony going to a little material left so i'm going to have to be very careful when porting the opening and I dont plan on porting the runners after looking at them even with the porting done to the wieand the LS6 seems have to better looking runners than the wieand So I guess its worth trying and my 85mm MAF has already been rescaled and tuned but for the weiand i'm hoping that the LS6 doesn't throw it off much if so I hope that the PCM can adjust atleast until I get my cam installed because I dont want to pay for anymore tuning until I install the cam.
Last edited by 1999BlueTA; Apr 10, 2009 at 06:22 PM.
My ls6 manifold is ported also. I have a ported 80mm bbk on it right now but I am fixing to install a P/P 85mm on there. If you port the ls6 out that far you will not be able to use the factory gasket, but you can use gasket maker and seal it on there. I think this manifold is one reason my car puts down really good numbers for the mods it has.
Ya I already know that I wont be able to use the factory gasket I plan on using the paper gasket that came with my PP 85mm TB. Did you port your runners also or only the mouth opening and do you have any pics of your intake?
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Regarding your comment about getting close to the FAST; it's really not an accurate comparison to compare the LS6 against a 90 or larger FAST. All over this site, you'll find threads about how one is better than the other & neither is true. The FAST is great & shines when using high lift cams & while spinning to 7K RPM. The LS6 is great for mild cams w/ medium lift & spinning up to 6.3K RPM. So, the truth is that they are both excellent intakes & should be selected based on your set up. Like I said, once youre airflow approaches 440+ g/s, the LS6 will benefit by porting the runners, but not until then.
Since your MAF has been scaled to an 85mm Weiand, I'd say that you are OK.
Since your MAF has been scaled to an 85mm Weiand, I'd say that you are OK.
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i had my ls6 laying around for almost a year befor i got around to cleaning the cobwebs out and putting it on the other day. i had planned to port it out for a 85mm tb befor i put it on so when i ran into a real deal on a tb i would be ready for it.... im just like the op and when looking at it, it didnt have alot of meat around the snout. right at the opening it would be fine, but farther up in the snout it looked pretty thin so i didnt mess with it. kinda wish i had exsperimented with it months ago while it was just chillin collecting dust. but didnt want to mess it up right befor i needed it and be waiting on epoxy to dry befor i could start it.lol
This is how it's done: (see pics). Tuning software is your best friend in order to get the best results. Also, & I'll say it again, don't open the runners unless your cam/heads can flow more than 440 g/s as measured @ the MAF. If you do, you'll lose low end power.
The inlet port is opened as shown & the area @ the intake is left alone. This creates a very useful funnel. A good cold air intake funnels from large to small into the plenum. That is what is created here. This passed slightly more air than did a straight through inlet port. So, I called it even. Must be willing to seal the remaining thin lip to the TB or TB adapter plate. I used an adapter plate to get a flat surface on the TB side & the intake side. Took me a lot of testing to get this, so please respect the information.
The inlet port is opened as shown & the area @ the intake is left alone. This creates a very useful funnel. A good cold air intake funnels from large to small into the plenum. That is what is created here. This passed slightly more air than did a straight through inlet port. So, I called it even. Must be willing to seal the remaining thin lip to the TB or TB adapter plate. I used an adapter plate to get a flat surface on the TB side & the intake side. Took me a lot of testing to get this, so please respect the information.
Well My cam is a mid 230 duration and over 600" lift In/Exh so its kind of agressive so im unsure if I would benefit from porting the runners I'm just going to leave them as is for now and if I decide to port the heads later on I will probably port the intake runners then and i'm glad to know that the funnel effect helps flow because it doesn't look like there's enough material to do much after the opening. Thanks for all the helpful info and pics guys I'll get started on my intake in the next day or two.
On The Tree
Joined: Apr 2009
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This is how it's done: (see pics). Tuning software is your best friend in order to get the best results. Also, & I'll say it again, don't open the runners unless your cam/heads can flow more than 440 g/s as measured @ the MAF. If you do, you'll lose low end power.
The inlet port is opened as shown & the area @ the intake is left alone. This creates a very useful funnel. A good cold air intake funnels from large to small into the plenum. That is what is created here. This passed slightly more air than did a straight through inlet port. So, I called it even. Must be willing to seal the remaining thin lip to the TB or TB adapter plate. I used an adapter plate to get a flat surface on the TB side & the intake side. Took me a lot of testing to get this, so please respect the information.
The inlet port is opened as shown & the area @ the intake is left alone. This creates a very useful funnel. A good cold air intake funnels from large to small into the plenum. That is what is created here. This passed slightly more air than did a straight through inlet port. So, I called it even. Must be willing to seal the remaining thin lip to the TB or TB adapter plate. I used an adapter plate to get a flat surface on the TB side & the intake side. Took me a lot of testing to get this, so please respect the information.
