verbs

After talking to a former Lingenfelter employee about having my heads flowed with the intake on, he told me that all LS1 head derivatives (the 5.3L and 5.7L heads) stall at .500 lift with an LS6 inake, while the LS6 head derivatives (5.7L and 6.0L heads) did not.

He said every time they flowed the ls1 derivative heads they'd stall (wouldn't gain additional CFM) above .500 lift with the ls6 intake on.

Is there any truth to this, and is there a possible fix like the LSX intake? I know ls6/6.0L heads are an easy fix (according to him), and maybe down the road AFR heads.

Thoughts?

niphilli

Not sure what he means by "stall". There are hundereds of peole using over .500 lift with great results with LS-1 heads, and I dont think it is all coming from duration. Might want to ask him to clarify what he means.

JoSeY

Huh? 1st off I thought the 5.3L heads were more oriented like the LS6 heads than the 5.7 or 6.0 heads...2nd...what does he mean by stall??

CAT3

iTrader: (9)

Stall I bet he means that the flow is disrupted so much that the charge is stalling or hanging up in runners/chambers or even the main plenum. although it obviously still flows air past that point, it would be easy for a set of heads to "stall" be more disruptive than smooth flowing, if they were designed to flow at a certian point. Design limitations. Just my guess though.

verbs

Bingo! We were discussing how ls1 derivative head flow (in CFM's) doesn't increase above .500 lift with an LS6 intake attached....a.k.a. port stalling.

Without an intake attached, most ported heads seem to have increasing CFM as lift increases, usally tailing off around .575-.600 lift or so.

Since heads on flow benches are usually flowed w/o an intake manifold attached, most assume their heads flow better and better as lift approaches .600.

verbs

1. you have it backwards, the 6.0L heads are more akin to the LS6 heads, and the 5.3L heads are more akin to the standard LS1 heads.

2. See the above post.

99 Black Bird T/A

iTrader: (4)

Post deleted by 99 Black Bird T/A

verbs

So is there a fix for the stalling?

99 Black Bird T/A

iTrader: (4)

Absolute says:

Radiused-ls1- ls6
200-159 -157- 159
300-217 -195- 212
400-272 -236- 259
450-288 -249- 274
500-297 -264- 288
550-304 -270- 292
600-309 -273- 294

That's 294 cfm with the LS6 intake in place @ .600 lift.

See this link for the details

https://ls1tech.com/threads/showflat...=7&fpart=1

99 Black Bird T/A

iTrader: (4)

Looks like Absolute might have a fix...I know I would like to know more.

99 Black Bird T/A

iTrader: (4)

TEA Lift LS1 LS6

.100 65.14 65.6
.200 133.1 133.5
.300 184.3 189.9
.400 217.1 227.75
.450 229.2 241.3
.500 236.3 250.2
.550 236.3 247.5
.600 235.7 245.18

Absolute-ls1- ls6
200------157- 159
300------195- 212
400------236- 259
450------249- 274
500------264- 288
550------270- 292
600------273- 294

I would really like to flow a set of Absolutes on SRP's bench with LS6 intake in place and see what the numbers are.

jaywoo

OK, I guess this is the time to ask this question then. I'm I'm probably kinda dumb for asking this. But...

Let's say the intake valve will flow 250 cfm at .600 (it's a nice round number) with the LS-6 intake attached. Since we have 8 intake valves, would that stand to reason that we are trying to flow 2000cfm? And if that's true, I'm pretty sure that our throttle bodies will not flow that. I saw a throttle body somewhere for $700 that advertised 1300 cfm. I have no clue what our TBs flow. Mine is ported and polished, and it probably helps some, but to what extent I have no idea. So, where I'm getting at I guess is "Is it important to have a really high flowing head, or is it better to have a very smooth flowing head?

Yelo

so, how do those flow numbers compare to stock 6.0 or LS6 heads....and does the same dropoff occur with those heads ??

2002SS#7339

Jaywoo, that would be right if all the intake valves were open at the same time, but they arent.

verbs

I'm told those heads do not dropoff. The 6L and ls6 heads flow quite a bit better than the 5.3/ls1 heads stock.

CAT3

iTrader: (9)

Jaywoo, the restriction for intake system is the bottle neck design of the TB mount to the intake. If you can flow 8,000cfm thru your TB but the intake opening will only flow 1,000cfm then your limit is 1,000. I am ignorant to what the cfm flow rating of our TB/Intake/ etc... are.

Also, you want a large enough runner to accomodate the flow of your cam, and narrow enough runners to keep the velocity high which will improve your fill, burn and expense therefore make more power. Smooth in some areas, like the bowl and rough thru the runners is appaearantly fine, as is the back side of the valve area. Form what I have gathered.

Charlie.

99 Black Bird T/A

iTrader: (4)

Per Absolute in the thread I put the link to above

"we have been getting alot of questions on intake flow with ls6 intake attached, every one feels the intakes are restrictive and could only flow a certain amount, this is false, Yes you will get a drop in flow with it attached compared to a radiused inlet, the restriction comes from both the intake and the head were the two meet at the floor of the runners, it causes a no flow area, the ls6 intake was revised by lowering the floor to give the floor of the runner a better approach to the floor of the head, this reduces the no flow or dead zone and improves flow, there are tricks to porting the short turn radius that also will reduce the dead zone and improve flow, there is no limit to the intake, the rate of flow loss is progressive and differs from one porters work to another, below I listed flow from our absolute speed stg2 ls1 port's with a radiused inlet, ls1 intake, and ls6 intake. port volume is 209cc's, 2.02 valve"

Radiused-ls1- ls6
200-159 -157- 159
300-217 -195- 212
400-272 -236- 259
450-288 -249- 274
500-297 -264- 288
550-304 -270- 292
600-309 -273- 294

They are claiming 294 cfm and no stalling with the LS6 intake in place with LS1 style ports.

99 Black Bird T/A

iTrader: (4)

Heres some more data I think C. Enders collected it orginally.

With Manifolds:
Cylinder Head Intake Manifold .200" .300" .350" .400" .450" .500" .550" .600"
My TEA 5.3's LS1...................133.. 184... na....217... 229.. 236.. 236... 235
Stock LS1 LS1.......................136.. 184... 200 .214... 222.. 227.. 229... 235
Stock LS1 LS6.......................136.. 186... 206. 223 ...227.. 236.. 241... 242
My TEA 5.3's LS6....................133.. 189.... na 227... 241 ..250.. 247... 245
Stock LS6 LS1........................156.. 199... 212.. 224.. 232.. 238 ...243 ...247
Stock LS6 LS6........................154.. 204... 220.. 235.. 247.. 257... 263... 265
Ported LS1** LS1...................141.. 185... 205.. 222.. 232.. 241... 251... 258
My TEA 5.3's LS6...................133... 189... na.....227.. 241.. 250... 247... 245
Ported LS1** LS6.. ................166... 211.. 229.. 244... 257.. 269... 277.. 283
Ported LS6 LS1.......................156... 199 ..217 ..230.. 242 ...253 ..263 ..268
Ported LS6 LS6.......................153 ...202 ..222 ..241... 257 ..270 ..280 ...289

* Original Stage II heads from New Dog, Old Tricks; GMHTP May/July 2000
** Latest revision.

This data also shows LS1 ports NOT STALLING at .500 lift

My TEA were flowed on a different bench, but the stall points for my TEA's are VERY LOW, LOWER than STOCK heads with the intake in place. TEA insisted I got the exact same heads as very one else.

LS1derfull

Stall of port in my findings has as much to do with flow amount as it does with being at a certain lift. Example: i flowed 5 liter eaters early ARE stage 1 head, it did not stall at .500" lift, flow went up to .650" lift. But it flowed at .650" lift what most current heads flow around stall point of .500" lift. If flow amount is low enough head doesnt stall untill around 285cfm is reached. Port size and shape are designed to balance swirl and great flow, above .470" lift the swirl seems to affect flow production of head.If porting techniques remove or push back this swirl characteristics of head, than much larger flow can be had. I would love to see Absolutes port mods to get LS6 intake to move that much air as they posted. This is a big advancement for us guys with LS6 intakes!

absolute speed

Here is most most updated flows and flows with intake attached on my new superflow sf 660s flow bench. My old bench was an older flow data bench that becuase of its lamnar flow element reads higher and will not detect turbulance like the superflow. Also with the new superflow with flow com, I can read leakage accuratly down to the tenth of a cfm, Flow data benches can not read leakage.
ls1 head flowed on supeerflow sf600s, 28 inches, 3.9 bore
lift-radius-ls6 intake
200-151-147
300-205-198
400-254-238
450-272-253
500-288-268
550-299-277
600-306-281
These are average flow readings, some heads will read a bit higher 2-3 cfm some a bit lower 2-3 cfm. The one thing I dont want to see from a head is stalling before the cams max lift then falling off and going backwards
One thing people have to keep in mind is every flow bench is different and the way it can be flowed can be different. It is important to look at the way the head is set on an ls1 block with no piston in it. If the head is set up the same way on the test bore with the ls6 intake and rocker bolt attached, then you will see how it will flow on the eng. I can get up to 5 cfm more If I flowed the head favoring the intake side of the chamber or flowing centered on a 4 inch bore. There are some other factors that play in but I dont want to let the cat out of the bag. Jfm is right, I am always trying new things and finding new ways to get more out of the heads, this is the main reason why I wont get my heads cnc'ed, the development will stop, Time will stand still and there will be no advances in porting tecnology.
Look for some results from my stg2.5 heads with the 2.040 intake valve, the reason why Im making this head is for its flows with the intake attached and to get the flow past .600 lift on ls1 heads, the 2.02 has a hard time going past .600 through the ls6 intake