As some as you guys know i've been in a few threads about getting
heads for my 2002 SS A4 project. I got a lot of great feed back from not
only members but also Tony from AFR, Jason for Texas Speed, Chris at CC Performance and many others.
So thanks all you everyone for your help...This has nothing to do with which heads to buy, but here's the question....I know it's been brought up and the LS6 intake and that it flows about 275cfm correct? Now the real question is : Does it make sense to port the heads that flow more than that what the intake can process? Aslo what limits the intakes from flowing that amount? Is it the TB opening? Or is it the individual runners themselves?
Now reason I asked this is back about 3 years ago I had a set of GTP 6.0 LQ9 heads flowed in Philly by an engine builder that knows about building power. He takes Pontiac Big Chief heads. Now from what I was told that the heads have large intake runners and flow more than what's needed. Now get this...he fills
in the runners to make them smaller to actually lower volume for sick velocity!! Thats wild..lol.
He fills the runners in by as much as 25% or more. He does this to the runner to crank up the velocity. And his cars do very well. So he was showed a set of 241 castings off a Camaro. He also filled the floor of the intake runner to shrink it down to something like 200cc's or alittle smaller. I was shocked when i saw them..lol. But all said and done the heads flowed less than 300cfm, but i apologize what the cfm number was, BUT the air speed was out of this world.
Now i think, the runner size was about 195cc but with velocity just under sonic boom speeds..lol. But not by much, serious about that...i'll get further stats. on LS based heads. Basically the vewlocity gets high enough it carries cfm with it. So you got all the air speed you need and the cfm gets carried in with it so the motor doesn't starve for air at hi rpm. BUT, i only saw this being done for fast n/a motors. But this same guy told me why do you need 300cfm for a little 346cid low reving street motor? But since he was flowing my blower heads he said "oh ok that will be fine " . Well i wanted to share what i found out about this stuff...its always cool to find out about new LS motor stuff.
Interesting too And since there's someone out there ready to nail me to a cross, i'm not saying that the AFR's or TFS heads and the others are made wrong cause they flow 300cfm+, thats not the case...i know these heads work i just thought i share this on here so guys know that velocity is important and that a large intake runner it's necessary better cause their runners are 220cc while some are 205cc's.

 

Several engine builds have also mentioned that smaller runners help provide higher air flow, and in some cases close to the speed of sound, which in turns produces very high low and mid range torque. and good high end HP numbers.

 

Why do you think the AFR 205 make such sick power with smaller cams than others?

Velocity, swirl etc.. basicaly serious airspeed in proper port design.
The proof was in the early AFR days when TEA ported some AFRs and the result weren't too great. Why? I think because they were messing with an allready fine tuned design.

 

Small port, high velocity heads have worked for years and years on small-block chevy's, it would only make since that it would do the same on LS motors as well. If done properly...

 

Mark,

Just like what you and i talked about earlier...Tony knows his stuff to be able to pack over 300+ cfm in a 205cc intake runner It takes more than just porting skills to pull that off...I forgot to get your opinion on 1 thing...with all the torque the AFR's make and that torque infested cam you recommended..hehe...do you think that i'll be ok with the Vig3200? Some say the Vig2800 would be a better fit since the head/cam setup would make so much low end tq. I know i had myself set for a Vig.3200 which is already a step down from my previous stall...a Vig.3600. I just think a great combo would be a Vig.3200 with a Trans-Go HD kit, and 3.42's for sure or at the extreme a set of 3.73's .
LOL...Hey Mark i must be getting punchy cause of being up all day, but i got a perfect name for the cam you spec'd for me...ready???
ONE FLEW OVER THE CUCKOO'S NESTcam!!!
HAHA...i know i'm getting tired..lol. But honestly i like it. I talked to a couple GM engine builders around my way and with the torquey style AFR heads and your awesome cam, plus long tube headers and most likely a new SLP PowerFlo CB.

 

If you want to keep it street I would say SS3600 Yank, VIG 3200 is a great stall but at 2.5 STR it is a bit loose for street. If you want more track then yeah VIG 3200 is perfect.

I run VIG 3800 and while I find it a bit of a pain for looseness, the way it hits make up for it.

 

Thanks Mark...i never tried a Yank, but i know the SS series is tighter than the Viggy's.
Now i used my Vig.3600 as a DD for a the last 2 years i had it and it seemed ok..the car
would roll from a stop light or stop sign just by lifting off the brakes a little. Is it true the
SS3600 hits harder too? I think my Viggy 3600 had close to a 2.5 str, but it's hard to say cause Precision doesn't call it STR they have another term. Something like Stall/Torque ratio...six of one, half a dozen of another...lol. My 3,600 hit wayyyyy hard on nitrous.
Thanks...i'm gonna look into the SS Yank verts. But after having a Vig.3600 since 2001, it would seem strange to go to Yank..lol. Like a Chevy guy buying a Ford. HaHaHa. Thanks bro..

P.S. How did you like the name for that cam? That cam will be INSANE
Den

 

Thanks y'all for popping in and talking about the AFR's. Sometimes when you see something
like a set of heads or a certain cam, or a nice girl something inside tells you that you should go for it...well the AFR's were just like that since i saw them way back in Vegas in the 2003 SEMA show...I met Tony and he was there from the time the place opened until it closed...i think they had to tell him when it was over...lol. Thats the way Tony is. He's not a slicked up salesman, he the real deal. He's the designer and knows what his heads can do better than anyone, except for all those guys in the California area with C5 Vette's that switched to AFR's from whatother heads those C5 guys were using before that. And those Vette's with the AFR 205's and the 224/228 cam were not only dynoing crazy numbers they were running serious times as well, plus I was glad i got the chance to talk with Tony himself from at Vegas...he talks so technical its hard to keep up with him...lol. I'm a better LS1 car owner since i met Tony. But also i wanted to thank the people with AFR's so i could make the right choice since there are a couple really good heads out there for what i have planned. Thx all .

 

Even if an intake only flows 275, you put a head that can flow more behind it, it will make more power. Why? Intakes don't generally flow a set number as they are extensions of the head design. On SBCs, I've seen an intake actually increase the flow of the head.

If you get a head behind the manifold making 350cfm, the whole intake track is going to make more power than one that only flows 300 (given that airspeed is close). But the way to get to 350cfm is with a runner that is much too big for a street-driven 346. If you look at the best power producing heads though, they have sick numbers in the .200-.500" lift numbers. These flow numbers that are actually within the effective range for the intake manifold and happen to be where the engine spends most of its life. So it makes sense to optimize this area.

To optimize this area, high lower-lift numbers come from effective, high velocity ports. These ports help draw air through the manifold due to the pressure drop. And don't just think about the AFR 205... look at the TFS 235 vs LS7. It's down a good 30cc to the LS7, but in the .200-.500" range, it flows very similar. The manifolds help support this, yes, but the entire intake system is flowing very well in this range and making power. There have been several comparisons here showing the TFS head making more power than the LS7 upto 6k RPM (with multiple camshaft designs), but after that, the LS7 pulls away.

Point is, the polymer manifolds have limits due to their design. It's best to work within those limits and exploit the strengths the manifold provides in both cylinder head flow area optimization and camshaft valve events.

 

Well said, also let us not forget Cam VEs and Lifts/lobe profile to add to the mix. Again we find the benefits of a "Balanced Combo"

 

^^you make a good point about the best heads make high flow in the mid-lift which is
true. And that proves my point about why do we need 300+cfm at high lift. The mid lift flow on the best LS heads are still close to what the LS6 intake flows...Thats why i was curious if we need more than what the intake manifold flows. The intake parts, ie..the airbox, filter, tubing and MAF and TB play the role as the whole intake tract. But i'm talking about the manifolds individual runners...if they flow 275cfm and a certain air speed, whats the benefit for a head runner to have the ability to flow as high as 300cfm? The intake manifolds runner is an extention of the heads runner. So it would seem that the intakes runners only flows 275cfm maxxed out at 28" of water...so some heads intake runner can flow as much as 300cfm+ maxxed out at 28" of water. So i guess wouldn't it be in our best interest to focus on lower to mid-lift flow and air speed and not go crazy worrying about hitting 300cfm or more?...Everyone's in love with bigger and better...every head i used on my LS cars since late '99 never flowed over 270cfm...and the runners didn't stall or become turbulant. But if i pushed the valve further on a flow bench i gained a few cfm but the air was becoming turbulant. So we let it alone and just kept it where it had the best quality flow, around 270-275 cfm. The car was plenty quick and didn't need a large duration or large lift cam. There's nothing wrong with high flowing heads, but i'm just curious to see what people say about this.

 

I have had great results with small runner high compression heads that flow 300+ with a 224/228 cam with a 110 LSA....been running it for the last 42,000 miles on a DD .... it has great manners on the street and makes great power under the curve which is perfect for my application...

 

It ok to have 300 cfm heads, but i'm curious id its needed, thats all. I know i want the
AFR's cause i love the small runners and since the mid-lift flow is great.

 

Well, you will exceed 275 if you put a 350cfm head behind it. How much? Hard to say. But since it is an extension of the head design, the manifold can cripple it, but 275 is not a set limit. You have to think of the manifold as providing a percentage of the total head CFM. If we could find wet flow comparisons of the manifolds, I think you'd see what I'm talking about when it comes to manifold flow is generally a percentage of head flow.

One other point: the FAST always seems to add 15-20rwhp compared to an LS6. From stock engines to 440cid engines. Why is that? Well, the stock engine, with its stock cam, can only pull so much through the LS6 manifold. Add a better intake, and it'll be less resistant and offer better power. The power delta can widen the more the LS6 restricts the engine, but there is a limit it seems to how much additional flow a FAST can provide. A 440cid engine is a good example - many times the FAST only provides the same 15-20rwhp gain, despite the fact that the engine requires a lot more air. That tells me that the LS6 is able to provide more air in this configuration than in the stock configuration - that the heads have provided a boost to the manifold. Otherwise, we'd see the same power out of 346 and a 440. We don't, although, we don't see the type of gains we expect to see, pointing to a manifold restriction.

300cfm is enough to support a heck of a lot of horsepower, so you should be okay with a manifold that comes close (Ported FAST is usually in the 285-290cfm range). And all new heads coming out are really putting an emphasis on that .2-.5" lift area to maximize power with these restrictive manifolds.

 

After reading Lingenfelter's site where they show a back to back test on a 427cid LS based engine. They compaired a FAST and a LS6 intake. I was alittle shocked to see that the FAST made little to no gain over a GM intake. some people on here think i dislike the FAST...thats not the whole truth, its that i think that GM does a great job on the LS6 intake. But to be totally honest i'm not a trendy person. I rarely just jump on bandwagons. Over $1,200 for a possible 15rwhp increase is really not the place for me to get the best horsepower per dollar spent, plus to get the most out of it you have to spend more to have it ported?? For that total cost you can get a set of coated AR headers w/high flow catted stainless y-pipe. Now thats a part that will always give u a great return on your investment. And there's little chance of any o-rings leaking or anything splitting or cracking. But my doubt in the FAST felt justified after i saw the dyno comparo. And i take dynos with a grain of salt. And i was lucky enough to install and retune the pcm for the TPIS on a stock bottom end w/heads/cam. I honestly thought it was gonna be a waste of money, but man i was proven way wrong. When i logged the MAF frequencies i could see how much more air the intake was letting the motor process. And it pulled hard as hell from mid-range on up. So in the case of this intake the gains were from the larger TB opening, and if i remember the TB snout was longer than the stock mounting snout which would help add alittle velocity. I just know it works. I think this intake was used on their C5 twin turbo vette. Unless theres something i'm missing when i read the dyno results, but i always ask guys that bought the FAST 90/90 or 92/92 what gains they see at the track. With the rwhp gains that are being claimed i would expect to see atleast 2 tenths and 2 mph on average. I'm sure those guys are out there but i know if i was in the market i would want to know what people were seeing at the track, not the dyno....All i like dyno's for is to get my A/f ratio to be a smooth line without any dips or spikes in my logging.

 

Bump for more on this question, I too have wondered the same, I also feel as you do about the fast, I am no FAST fanboy for sure, like you said 1200+ for 15RWHP, not for me. Good for a guy with tons of money that wants a dyno queen, but I have to have bang for buck. (My wheels were an investment so they dont count, figure someone may bring that up, they will sell for more than I paid)


As far as the dyno tests go, there are other tests out there showing an actual loss in power below 6k. I too try to take them with a grain of salt but the more test you see with the same results.........

 

After you do the heads/cam and the rest of your free mods and bolt ons the last 15-25 HP is going to cost you more than the big HP jumps you got for your heads/cam..as with any engine squeezing the last HP out of it will not be as cost effective as your basic mods ... ya gott pay to play ... on a street only car those last pew ponies are probably not worth the investment to a lot of people...

 

I love the small runners on the AFR's and the Terminators, but i took a look
at the fastest n/a cars alot of them are ported GM castings. Just thought
that was interesting.

Den

 

it's not just about the volume of the intake port,but more about shape,especially the short side radius..you can have too much velocity if the port is not shaped correctly to benefit from the increase in CFMs..i read somewhere that GM had at one point too much velocity in the intake port when first developing the LS1 heads..i'm assuming the air couldn't make the turn around the short side effectively...
think more about the proper CSA and port shape then port volume..

 

Now with that said, about flow number with heads and intakes what about the throttle body to match intake how do you determine ?? how much does the throttle body come into play ??