don527

I just came back from Barnes&Nobles and saw the Feb 02 issue of Car Craft and I feel they had a great article, a how-to on head porting. It gave a lot of info on the aspects of ported heads and I recommend it to anyone that wants to know more about it.

I always read on the forum about people asking about H/C packages from various tuners and "who's better" and "what size valves" and stuff like that. But I don't really recall anyone giving flow numbers on the heads in question and how each tuner compares as to what kind of flow numbers they are getting. Do tuners keep that a secret?

In the Car Craft mag, they show a formula that show a direct relation of potential hp obtainable to the flow numbers from the heads. I wrote it down, it was:

hp = cfm x 0.2575 x number of cylinders

In that article they had stock heads flowing at around 195 cfm (going by memory) and it dynoed close to 400hp which is inline with the formula and with only the addition of ported heads flowing at around 250, the engine dynoed a lot higher... not the 500+hp that the formula would theoretically calculate (I think it gained 40+ hp from porting alone which impressed me) but said the heads had potential to support a 500hp engine.

I think that there is no question that tuners like MTI, ARE, LPE, Norris, DRM do quality work so you can't go wrong with these guys for work. But now I wonder, what kind of flow numbers are the tuners getting with their Stage I, II, III heads and maybe we can compile a chart to examine how each tuner stacks up with each other. LS1 and LS6 heads.

Can anyone contribute your flow numbers from your H/C work? Tuners, can you? Am I wrong in thinking that flow numbers are that important?

What are the flow numbers from stock LS1 and LS6 heads?

I hope to get some feedback :) I wish I had bought the mag now... for $4, it would have been worth it.

Don


[Modified by don527, 10:47 PM 1/4/2002]

Mean Green

cool info and great questions....count me as "one of those asking questions" :D

and don't forget those truck heads that are supposed to fit, what ever the hell that is?

Chris@SD

These are the Lq9 heads, but they have a larger combustion chamber for lower compression.

That formula leaves a lot of considerations out. According to that formula, the last set of stage III heads I sent out could make 655+ HP..... Now I do think our heads are some of the best on the market, but even I would not venture to say that good. :D

Mean Green

hey Chris....I still wanna talk....I'm gathering numbers and quotes from different vendors now on h/c packages and can't wait to talk....maybe you could send me a preliminary email outlining what's available, prices, etc :D:D:D

don527

Not that the ported heads alone would give you 655+ hp but do you believe that it is true that with flow numbers as high as 318cfm, that you could build a 655hp engine around those heads? I think that's what the formula shows. :yesnod:

Would you like to be the first and give us some flow numbers of your ported LS1 or LS6 heads and how they compare to stock?

I wish I had bought that issue of, I believe, GM High Tech Performance Magazine where Agostino of ARE contributed data comparing ported LS6 heads to Ported LS1 heads. He didn't seem to have any problems giving out numbers to the magazines.

Don

Paradigm

These are numbers from my own heads, all done over the past several years. These are all LS1 castings. Plenty of higher velocity, better flowing heads are available today..... but this gives you some numbers to eye. Remember, these are nearly two year old data points.

I am working on a new motor and the heads will be the latest - I will post a comparison when done (several months away)

<BLOCKQUOTE>code:<HR><PRE>
Intake Exhaust

Lift Stock Stage I Stage II Stage III Stock Stage I Stage II Stage III

.100 90.4 72.4 73.8 77.4 57.1 60.2 61.4 64.6
.150 125.1 133.2 135.9 120.9 86.1 91.6 93.5 95.6
.200 150.4 150.4 154.2 157.0 106.0 115.7 118.7 124.1
.250 182.7 186.5 190.2 188.5 127.9 135.7 138.6 154.2
.300 203.4 208.5 212.7 212.1 144.8 153.1 157.1 173.4
.350 220.6 231.4 237.4 239.3 163.6 171.5 175.9 190.9
.400 224.5 246.9 254.5 263.7 175.1 185.0 190.7 203.5
.450 228.4 262.0 271.2 282.9 183.6 195.0 201.6 210.0
.500 231.4 265.4 276.1 296.2 192.8 203.6 211.9 216.3
.550 241.0 270.6 284.3 302.1 196.7 206.4 216.8 221.5
.600 250.2 274.0 288.1 302.1 200.5 210.0 220.5 224.9

</PRE>[/QUOTE]


[Modified by '98 Six Speed, 10:56 AM 1/5/2002]


[Modified by '98 Six Speed, 11:01 AM 1/5/2002]

don527

Awesome post... thanks '98 and can't wait to see your updates in the future. Is that from a DRM built motor?

Hopefully we'll get some more input from other people and compare.
I'd like to see how stock LS6 heads compare.

When people get H/C work done to their vehicles, does the tuner provide flow numbers of the heads on paper so that you know what your buying? I would have thought we'd have seen a few posts of them over time like people post dyno numbers.

Don


[Modified by don527, 2:42 PM 1/5/2002]

don527

Before we start getting into the differences between flow benches and temp and fudging of data.... Let's just see the data first and then figure out the details afterwards.

Anyone posting numbers like dyno numbers are getting the data from the shop and are taking it on their word that those are honest numbers and we should treat them that way. We can wonder the technicalities later.

You don't see me asking about what flow bench was used in the Car Craft mag or what temp or whatever... I want people to contribute numbers so that, as a group, we can learn from them, and if there are fudged numbers, make that determination as a group. If there are technical variances we can make the corrections. But if we kill this thread before it even starts, we learn NADA.

The horses haven't left the gate yet and don't want to talk about which horse is doped up... Let's race first then figure it out.

Don


[Modified by don527, 2:40 PM 1/5/2002]

Chris@SD

Sure, I will post some. Here are flow numbers to the latest Stage II heads that we have done.

Stage II (2.02/1.570)
Intake
.200........173.8
.300........235.4
.400........266.7
.450........276.4
.500........286.1
.550........294.2
.600........296.7

Exhaust
.200........115.2
.300........152.2
.400........187.4
.450........201.3
.500........211.2
.550........219.6
.600........222.7

These heads were ported around a cam with a lift of .540 and are LS1 castings.

Stage III(2.055/1.585)
Intake
.200........158.8
.300........209.9
.400........262.4
.450........280.3
.500........295.7
.560........305.4
.588........313.2
.594........317.1
.600........316.3

Exhaust
.200........114.3
.300........154.6
.400........188.4
.450........205.1
.500........214.4
.550........221.3
.600........224.8

These heads were ported around a camshaft with a lift of .591.

As you can see from our flow numbers paired together with our camshafts, we do not have a generic Stage II or Stage III head. EVERY Set of heads that we do are taylored specifically for that setup.

If you call us for heads, before we say our stage II heads and this cam are what you want, we will talk to you and find out what you are looking for, what the purpose of the car is, Drag race, road race, daily driven, wekend car, HP desired, etc.etc.. At that time, we can then begin to pick out a cam and heads for YOUR APPLICATION

Anyway, let me know if you have any questions.
Thanks,
BTW, the above Stage II flow figures were aquired on a Flow Data flowbench on a 3.900" bore without a head gasket, at 28" of H2O at a temp of 74* degrees.
The Stage III were done on a 4.030" bore (as that is the size bore of the engine the heads were going on) and the temp was 76*

Chris@SD

You are correct. I will remove my post and we will see what kind of data we get first. :yesnod: :yesnod:
Thanks,

Mean Green

guess I'll be calling you then to start down our discussions :D

don527

Thank you. Very :cool: and I hope this thread provides some useful info.
(and I edited a previous post to reflect yours accordingly)

Don
[Modified by don527, 2:41 PM 1/5/2002]

John Shiels

I think (99%) my heads were over 300 @ .500 but I didn't bolt em on yet! I don't have he exact numbers but will ask. Far as I can read that isn't everything anyway.

don527

Are those the Vette Doctors S3 Heads listed in your sig?
Are they LS1 Heads?

I guess flow numbers aren't everything in the big scheme of things but in respect to the heads alone... isn't flow the only thing that matters?

If over 300cfm, your numbers are very close to Chris' S3 so I would think that if they are LS1 heads, and from the other posts, I would gather that 300cfm is the ballpark figure for a S3 setup with bigger valves and updated valvetrain.

What I'm waiting for is some LS6 info to see how much over an LS1 it flows stock and ported under different stages.

What I also want to see is whether there is a big significance over a S1 with stock valves and stock seats over a S2 with bigger valves but retaining stock seats. If someone can build a "better mousetrap" in a S1 config that flows as well as a competitors S2, then why go with the extra bucks with a S2 when you could have a decent S1 setup?

Don
[Modified by don527, 8:18 PM 1/5/2002]

houseofspeed

Don....I can tell you that my 2.02 LS6 heads are in the same neighborhood as those that Chris mentioned. Ported to ported the differences in flow numbers are negligible. Again this brings us back to the point that flow numbers are not the end all......

That potential HP theory is one supported and championed by Harold Bettes of Superflow fame and fortune. Mathematically possible....but not always the case in the real world.

Not sure I understand your point about going to a bigger valve and retaining the stock seat???? That is not possible....and as an FYI, the seat area is where the majority of improvements are made in terms of air flow....compared to the other modified areas of the port. Something to consider as well....the "port" is not confined to the head.....the intake port begins at the filter/air inlet and continues to the chamber....the exhaust port begins at the chamber and extends to the tip of the tailpipe. SO don't limit the field of vision to the head by itself.


[Modified by houseofspeed, 10:06 PM 1/5/2002]

ChrisB

Kyle mentioned it above, but nope there is quite a bit more than just flow numbers. Ignoring for a second the massive differences that can be achieved with different benches, setup's (one biggie is are the exhaust numbers with or without a pipe - that alone can make a huge difference and some people (not here) don't think it's worth mentioning).

But ignoring that there are still plenty of other factors. Flow is just a measure of the heads restriction. A higher flow value equals lower pumping losses. But what about mixture quality? You can kill all swirl/mixture motion in the heads and get some stellar flow numbers - but if your fuel falls out of suspension/your charge quality is poor you are still going to be down on power.

And also realize that flow measurments are a static value. They tell you what the head flowed at a certain depression (normally 28" H2O). But the engine doesn't work like that - depression increases with piston velocity in a fixed configuration motor, so changes throughout the cycle. Things like larger pistons, different r/s ratios, etc. can change the dynamics. Flow at a static depression is a good indication of performance, but those numbers alone don't indicate fully how it performs in a non-static environment.

I would submit that a good set of heads will generally have a good flow sheet, but a good flow sheet alone does not make a good set of heads. The flowbench is still an awesome tool - but it's just that, one tool in many.


That said, I still find all the flow numbers interesting, good thread! :)

don527

Thanks Kyle and Chris for the tech info...

Definitely quite a bit of info to absorb but that's cool... That's more info than I knew before. :)

Kyle, I think I was talking about a Stage I where they retain the stock valves and the stock valve seats with a 3 angle valve job vs. a Stage 2. In a Stage 2, my impression was that the stock valve seats are still retained with a 3 angle valve job but that those seats can fit a bigger valve than what comes from the factory. And then my take on a Stage 3 setup is where bigger valves seats are used to handle much bigger valves installed.

Am I correct in my thinking or completely off?

Then my argument was that if you could get flow numbers from a Stage I setup that were comparable as anothers Stage 2, then why go with the extra cost of the Stage 2? Just get the best flowing heads for your buck and hold on.

But now you and Chris have added a few more things to think about and learn like swirl motion and mixture quality and take into account that flow numbers, being a "static" value, may not work out exactly in the "real world" as you point out so that I guess there is some "art" to port/polishing as well as science.

Don

ChrisB

Stage I, II, III is really a misnomer - or at least a huge source of confusion. There is no standard, and it varies from vendor to vendor. Some vendors include new seats in stage II setup's - and price accordingly with other vendors stage III setup's. Some stage I heads cost as much as other vendors stage II setup's, allowing them to say "look, our stage I = your stage II". As far as valve job's go, we only do 5-angle valve jobs normally (as a minimum) - a good valve job really isn't that much more, and is not some place you want to skimp on.

I still think instead of classifying heads with stage I, II, and comparing them like that (which can lead to some strange comparisons - 600 dollar stage I's vs. 1500 dollar "stage I's", etc. I would say for most of us (me anyway) bang for the buck is a good comparison. I look at heads that are priced similaraly, since that's one of my main qualifying factors. If the stage II heads cost 3000 dollars I am not going to honestly compare them to a set of 2000 stage II heads, etc. I would look at power output/track times primarily, flow numbers for fun, and the hardware the head itself is set up with vs. price.

don527

ttt

john page

I believe LPEs (stage 1) heads flow in the upper 290s
better than most vendors (stage 2) heads.
Don't read to much into the "stage" # the flow # is what
making the power and how broad the power band is,almost anyone
can do pocket porting and slap in a big cam and make decent peak
power #s.Give LPE a call and someone can give you more specifics.