# another u flow versus x flow



## 8v.streetec (Jul 4, 2011)

well due to a balls up at the engineers i have to build a new head. Always have been under the impression u flow heads flow better. As im moving the injectors to outside my trumpets the exhaust proximity worries me a bit but will do anything that gets me more power. Setup is 340 tt cam tt 42/35 valve train(thank you tax man), 83mm16v pistons , toyota 45mm itb(have manifold) manifolds will be custom made as im changing the tuned length. Any thoughts would help thanks


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## ny_fam (Apr 3, 2004)

I like the cross flow better, ports well and flows well with the proper valve job.


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## 8v.streetec (Jul 4, 2011)

thanks for the input was leaning that way just for the fact i could channel air straight into the throttles


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## Glegor (Mar 31, 2008)

8v.streetec said:


> thanks for the input was leaning that way just for the fact i could channel air straight into the throttles


the intake ports are much less harsh angles on the u flow head.

there pretty much right angles on the x flow head.. not nearly as sharp of angles on the u flow..

i agree, intake directly above exhaust does not make a good plan, but neither do right angle ports in the head..


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## WaterWheels (Aug 14, 2005)

Sorry, but what you said about the cross flow (ABA) cylinder head vs. the counter flow cylinder head is not correct. I have linked some cutaway pictures which I believe can still be found here on Vortex to show what I mean. Both exhaust ports are what you could describe as 90 degrees from the valve position. The counter flow is worse and you can see that in the pictures. Exhaust ports are not as critical as intake ports are due to the gasses being under “pressure” (expanding)and being pushed out of the chamber by the pistons upward motion. Better design will help in the exhaust ports but a little sharp bending is not all that bad for them. From the pictures you can see that the intake ports are much different between the two cylinder heads. The cross flow has a much better angle of attack for the incoming mixture as opposed to the counter flow. It is also much cleaner in that the casting is better and the guide does not interfear as much. The counter flow is nowhere near a 90 degree bend like the exhaust port is but also nowhere near as good as the cross flow. It has been written in performance manuals and stated by people who do head porting that the counter flow head can be made to flow more than the “stock” cross flow head. It has also been written that a ported cross flow head will out-flow the ported counter flow head, that goes for stock vs. stock also. I could be proven wrong in some example or another, but cross flow heads are always prefered to counter flow ones as the path for the in-coming mixture and out-going gasses is much better. Yes, the heat factor is also better if the intake is not near the exhaust, but the flow path is much improved by having things moving more or less straight through the chamber.

Counter flow exhaust








Cross Flow exhaust








Counter flow intake








Cross flow intake


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## 8v.streetec (Jul 4, 2011)

thanx for the info guys especialy the cut away pics now at least i know how far i can port the head


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## Glegor (Mar 31, 2008)

i think you have the pics labeled backwards. ive seen them before. in the original thread.. thats where i decided that the counter flow had better ports.. 

again, ive seen these pics before, and i swear you have them labeled wrong.

if im wrong, right on, heres a cookie..


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## WaterWheels (Aug 14, 2005)

Glegor said:


> i think you have the pics labeled backwards. ive seen them before. in the original thread.. thats where i decided that the counter flow had better ports..
> 
> again, ive seen these pics before, and i swear you have them labeled wrong.
> 
> if im wrong, right on, heres a cookie..


After reading this response I noticed that the thread which the original pictures are in is at the top of the 8V forum page today (Porting the 8v head....). You can find them on the first page of that thread if you care to check it out. Although I labeled the pictures I posted (not mine, stolen) at the top of each one for anyone reading to understand, if you have done any work on the two different cylinder heads the labels would not be needed as it is obvious which is which. And you can keep your cookie for whenever you get hungry :wave:


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## dogzila22 (Apr 1, 2008)

Counterflow head cut is not from GTI head, but from carb head GU engine, original link http://www.ffp.fi/index.php?mid=2&pid=98 imukanava is inlet, pakokanava is exhaust


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## Jettaboy1884 (Jan 20, 2004)

Ah, the good 'ol Counterflow vs. Crossflow debate!

Here's a link to the Porting thread, which has a lot of good information: http://forums.vwvortex.com/showthread.php?4628897-Porting-the-8v-head.....

Someone please correct me if I'm wrong, but I believe that if you swap 7mm stem valves into a stock counterflow head, it will flow within a few CFM of a crossflow.

With that being said, here's my take on the subject:

This is very useful article that I like to reference. It's all about two-valve heads, so the information is largely applicable to this discussion:

http://www.popularhotrodding.com/tech/0610phr_cylinder_head_porting/index.html

I want to point out a few key things that are mentioned in the article:

For a "swirl port" head, a higher port approach angle is preferable because it leads into a straighter throat as it approaches the valve seat.

The crossflow head is (easily seen on the cutaways) not optimal in either of these regards. The short side turn (right before the seat) has a very sharp angle, and the port roof approach looks like it's trying to direct the air diagonally across the valve head as it fills the cylinder. Because of this, the throat is almost non-existant.

On the other hand, the counterflow head has a higher approach angle, and a taller throat, which tends to favor good flow around the valve head, and a better swirl.

The article also mentions flow bias, which is very important. I've posted a picture below of a counterflow 8v head, which clearly illustrates the port bias. Now, I may be wrong, but the counterflow head looks like it has a bit more room for working the port bias.

Here's a decent overview of head ports on Wikipedia. Note the high port approaches as found on two-valve race heads: http://en.wikipedia.org/wiki/Cylinder_head_porting

With all of this, and a lot of other reading/research, I personally feel the counterflow has more potential in NA form. 

Here's some old discussions (read through, as there's a lot of back and forth).

http://forums.vwvortex.com/showthread.php?209847

http://forums.vwvortex.com/showthread.php?129595

Unfortunately, the 8v aftermarket doesn't get much attention anymore, and there are few companies investing the time and money into maximizing the naturally aspirated power from 8v's. Back in the day, companies like Eurospec, Bertils, Techtonics, & Drake did put a lot of effort into the counterflow heads, but once the 16v came out, the later crossflow 8v didn't get that same kind of attention.

Here's that airflow bias pic:


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