c5blkvette

I hear a lot about having high flow numbers but then I look at Cartek heads (in which they make a point not to take out too much material) and compare to their 1/4mile times, and begin to wonder if the true test of a head is velocity (ie. people should be stating their flow numbers & more importantly their port volumes)

The question is: What is the intake and exhaust port volumes for AS, TEA, Patriot, Cartek & AFR heads?

Ie. Do some of these head porters sacrifice port volume to achieve high flow numbers (purely for marketing purposes)?

ROGERSPERF.

You are wright on with that the same happens with dyno numbers.Unless you can compair things on the same machine you do not get the true pictuer.

AINT SKEERED

iTrader: (2)

My head porter only did bowl work and a valve job with 2.02 int and stock exh valves. He got them to flow 262 at .600 and exh was 222 at 600 with great mid lift numbers for what the peak was. He told me he could easily get more but for a street car he did not think it was wize. With just a c1 .222/.222-.566/.566 cam On a112 lsa at full weight of 3726 my car hauls ***. It may not be one of the fastest on here but it is a great feel to hit the gas and have so much tq that it has down low.
JSears had GTP stg 2 heads and a TR230 cam and from 2000-4000 I had 20 ft lbs of tq on him . after that the big cam started to pull away. He has FLP headers and I only have Macs. I would love to see what kind of tq I would have with Long tubes instead of midlengths but the car pulls good like it is so I dont want to change it.
I thought about trying Futrals F11 cam and get a 3 inch y pipe built but that may be when its time for a rebuild which I hope is a ways away.
I do not know what cc's my heads are now but not much was removed and the car feels like a true street warrior. 23 miles to the gallon and runs 11.6's on Nittos with low 1.7 60 fts.

Not giving my self flowers or nothing but it just shows that when you get 300 cfm with a small runner you will have a beast of a car compared to one with 300 with lots of port work on stock heads. If I ever change heads it will be after the results of AFR heads start comeing out on the track. DYNO means squat to me.

Donovan

I believe the true way to compare cylinder heads is to find the smallest cross section in the cylinder head and then find the top flow number. Now divide the top flow number(cfm) by the smallest cross section and you will get CFM per square inch area. Example: your heads flow 300 cfm at say .600" lift and the head has a cross section of 2.00". Your flow per square inch will be 150cfm. Now your buddies heads also flow 300cfm @ .600" lift but his smallest cross section is 2.25". So his flow is 133.33cfm per square inch. Which head will work better? The smaller head will work better and have better throttle response. The problem here is that no one doing LS1 cylinder heads can tell me what the smallest cross section of their heads are. I have called all the head guys and nobody knows.

Richard@WCCH

iTrader: (3)

I didn't get a call..........

Those that have logged weeks or months flow testing LS-1 heads are aware of the sensitivity of the valve seat area thus making the port cross section area less important than you'd think. If the seat profiile doesn't compliment the port bowl and chamber shape then flow gains from port sizing and shaping will not be realized. Seat shapes will also influence port flow at various lift points along the curve. For example, I can test two CNC ports, one with a certain seat profile and another with a different shape. One port will show great flow along certain points of the lift curve and the other will not. Conversly stock port flow can also be enhanced with proper valve seat shaping.
Give it a try and let me know if you see similar results.

Cheers,

Richard

Bowtieman4life

iTrader: (1)

Keep this post going. I want to learn more.

ssvincels1

i know Tony's gonna jump in here at any time now
get 'em
the afr's are only 205 cc intake for the small ones and they flow pretty damn good
think stock port is like 205 for an ls1 head?
225's PLEASE!!

Donovan

You are correct Richard I didn't call you but I did call AP engineering, Futral, Patroit, Absoulte, Tea and Texas Speed. I even called Tony at AFR and he didn't have the info, he thought it was around 2.00". He said to call back in a couple weeks.

c5blkvette

Yes, I know Tony @ AFR keeps bringing this point up on this board. His new heads dont have to have flow numbers that are huge... because his port velocitys are high and will produce much more torque = acceleration. I was going to go down the stg2 LS1 route but decided to buy some LS6 castings as a starting point instead.

I would love to see a table of all the porter's heads with the flow numbers & also lists port volumes and minimum port cross-section. Anyone?

c5blkvette

ttt..

Donovan

I thought more people would be interested in this post. C5blkvette you have a PM.

Nickn20

you guys talk about TQ at 2-4k what does that really matter with racing where the rpms never drop below 4500 rpm? for a street car, yes 2-4k TQ is fun, make your tires spin, etc in the end in a straight line race who is gonna win a car that makes more TQ 2-4k or a car that makes more over 4k? just curious...........

this is provided both cars are setup properly for their power band.

Cstraub

iTrader: (1)

Velocity, point to ponder at 6500 rpm. How fast does that intake valve open and close on a given cylinder at 6500 rpm? Now knowing that air and fuel are needed to make power, do you want a volume or velocity. . . .???????????

Chris

OWENMUSTANG

iTrader: (2)

flow & runner volume (velocity)are only part of the total picture.
example in one of the 5.0 head tests mm&ff tested a brodix ported head against
the afr 185 head. on paper, the brodix equaled or bettered the afr at just about
every measurement(both were about 185 in volume) however, the afr won on the dyno by larger than expected margin. perhaps tony could chip in on why this happened..
seems like balance factors somewhere into this, valve angles maybe??
the more i read about heads the less i seem to know...

c5blkvette

Tell me about it! I have decided on LS6 heads (genuine) with cleanup and 2.02/1.575 valves...already sourced the heads.

kumar75150

when is AFR supposed to get a set of their heads on a dynojet?

Tony Mamo @ AFR

iTrader: (13)

In a few weeks....I should be bolting the AFR 205's on the car this weekend, as well as the cam and manifold we ran on the dyno test seen on our website. It will be a very user friendly and fairly mild street/strip package (224 Intake lobe), that we hope might produce over 440 HP @ the wheel, although I would say that anything over 425 would be fairly impressive with that small a cam. It seems more and more people are opting to go larger these days, but we were looking to feature what we consider to be a somewhat 'stealthy" and very potent street engine, where idle quality and driving matters are still a concern to the owner. Certainly more cam timing equals more power, and this combination is only one of many, but we hope the attributes of the all new AFR head shine in this particular test.

Now....Lets talk about velocity....LOL

My take on port flow and velocity.....you can't have enough of both. In simple terms, CFM quantifies how much volume of air the engine is capable of ingesting and of course mixed with the correct amount of fuel is capable of "X" amount of HP and TQ. More CFM, assuming the manifold and other restrictions are actually letting the motor see it, always adds up to more power potential. Now lets look at velocity, or efficiency in my book. Take the same 300 CFM head at .600, one runner is 200 cc's, the other runner is 230 cc's.....which head has higher airspeed and a more efficient port? That answer is easy. Chris, you brought a good point earlier to the table...Volume or velocity? If both heads flow 300....the volume is the same. If one head accomplishes this thru a much smaller cross sectional area, that head also provides higher airspeed and all the benefits that go along with it. Better cylinder filling, less likely to cause reversion, better fuel atomization (especially in a non-EFI application), more low speed torque production, increased throttle response, and the ability to knock down better fuel economy when your not romping on the gas pedal. Also, lets consider the scenario you mentioned earlier of 6500 (or higher) RPM's for a minute....At roughly 55-60 intake cycles per second, that doesn't leave a whole lot of time for the engine to fill the cylinders....I'd rather have the ports that move the same volume of air more rapidly to try and quickly squeeze as much air and fuel in that cylinder in the fraction of a second window you actually have.

Is the above paragragh gospel?....Of course not....Is it up for debate and other peoples different interpretation of the same events...most definately.
But ask most engine builders how a high flowing, efficient cylinder head with conservative port volumes actually runs at the track, be it an oval or a straight line, and I think most would agree they usually run exceptionally hard.
The above paragragh is the theory AFR believes and subscribes to be the most effective, and we pride ourselves at trying to build the most durable and efficient set of heads for a particular engine family. We also strive for huge CFM figures as well, and in a true heads up comparison, I am confident we would be in the company of the best of the bunch, but what we won't do is open that port up another 10-15 cc's for an extra couple of CFM at a lift point most engines rarely see. In our opinion, the cylinder head just became less efficient.

So all of us at AFR hope to see further proof of what we believe and "theory" become reality as a certain silver coupe will be hitting the rollers shortly....It looks to be a good time, so stay tuned...

And if haven't said thanks for your patience in awhile....lol

Regards,
Tony Mamo

JoSeY

Nice post Tony...always very responsive and with very knowledgable posts.

c5blkvette

Thanks Tony... This explains the volume vs. velocity theory very well. It was for this reason I decided on the LS6 heads over stgII LS1 heads. These heads will tide me over for a couple of years and then I plan to get a set of the AFR heads.

Efficiency is the key for me... and goes some way to explaining why a lower flowing head can outperform a higher flowing head in real life. ie. the high flowing head may look better on paper but if it is not filling the cylinders with air, the engine cant burn any extra fuel.

grooves12

Here is an interesting theory on 4-stroke engine operation and why VELOCITY is important to engine development. The website is geared toward motorcycle engine, but the priciples still apply. The guy is a little quirky, but his theories make sense when you think stop and think about them.

http://mototuneusa.com/the_8_phase_motor.htm

This guy has been a top motorcycle engine tuner for quite some time a high-velocity heads are the key to that (he modifies stock motorcycle head ports to make them SMALLER) and sees great performance gains with NO other changes.

A bunch of other interesting articles by him (if not off the wall) are here:

http://mototuneusa.com/thanx.htm