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High Flow, Low Cost, 8V Cylinder Head Project

 
Old 11-03-2013, 01:29 PM
  #106  
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Originally Posted by 67King View Post
It depends. Smooth ports are great if the air doesn't need to turn. If it has to turn, it can separate very easily, creating a vena contracta (essentially a choke point from stagnant air) A rough port will disrupt the boundary layer, and prevent the air from separating as easily.

So if the port is tight and has a small radius, you don't want it to be very smooth. If it is darn near upright, and the air has to turn very little, smooth is probably better.

While the 951 has some of the best ports ever because of the shape of the head, it is best to err on the side of keeping it a tad rough. The extra flow from a perfect surface is minimal, but the penalty for separation is HUGE.
My thinking is that this would apply equally to the intake runners? Would this not be a downside to a extrude honed intake as the short side radii are smoothed?
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Old 11-03-2013, 01:43 PM
  #107  
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I am hopeful that you are able to dyno test the extrude honed intake to let me see how much money I wasted after reading Harry's post.

However, all the new composite intakes are very smooth bore on the inside and have many curves, so I am still hopeful as to positive results.
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Old 11-04-2013, 06:06 PM
  #108  
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Originally Posted by URG8RB8 View Post
I am hopeful that you are able to dyno test the extrude honed intake to let me see how much money I wasted after reading Harry's post.

However, all the new composite intakes are very smooth bore on the inside and have many curves, so I am still hopeful as to positive results.
It isn't the number, it is the radius of curvature. And also you want to avoid S-curves, unless you have a straight about 4*ID long. I think 3 and especially 4 may be pretty compromised on our cars. If you have to make curves, making them in the same direction is always the way to go.
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Old 11-04-2013, 06:09 PM
  #109  
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Harry:

So what is your prediction on the extrude honed intake, good, bad, no difference at all???
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Old 11-05-2013, 12:02 PM
  #110  
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Eric, I think you'll be fine. Had to go back and re-read for the context. Extrude honing from my experience (which is minimal with it) is great for cleaning up cashing flash and stuff. It generally doesn't give a polished like finish. I think to get a really, really polished surface, you'd have to run multiple passes, which would remove more material at turns, and make the resutls bad. But overall, I think you'll probably see a small improvement. My "too smooth" caution was really that some folks will port and polish the heck out of intake ports, and if the short side is too tight, air will separate.
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Old 11-05-2013, 12:53 PM
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Whew!!! Thanks Harry, guess we will find out soon, Shawn has it for testing. I put the most likely too smooth LR intake on the FL car and took this one off. I just liked the way it looked, really no other reason. If the EH intake really has any benefits, I might through it on the CA car later.
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Old 11-06-2013, 11:07 PM
  #112  
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What you'll find, with enough flow bench testing, is that it's all about the shape of the port rather than the surface texture. Work on the shape!

Keep in mind that head porting is really 2nd semester stuff because it's not intuitive. There are people that do nothing but cylinder heads and some of them can really boost the power. Sometimes you're way ahead if you farm some of the work out. Cylinder heads, in my opinion, fall into this category because it's so easy to go backwards.
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Old 11-06-2013, 11:28 PM
  #113  
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Originally Posted by michaelmount123 View Post
What you'll find, with enough flow bench testing, is that it's all about the shape of the port rather than the surface texture. Work on the shape!

Keep in mind that head porting is really 2nd semester stuff because it's not intuitive. There are people that do nothing but cylinder heads and some of them can really boost the power. Sometimes you're way ahead if you farm some of the work out. Cylinder heads, in my opinion, fall into this category because it's so easy to go backwards.
Michael - I am sure you are right. In the end I am pretty sure I will be having you do an 8V head for me. As always, really appreciate you input.

I think I am going to spend a bit of time on this and see what I can do. No matter the outcome, I am sure I will learn a lot and to me that is the fun of it.
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Old 11-07-2013, 02:48 AM
  #114  
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Originally Posted by michaelmount123 View Post
What you'll find, with enough flow bench testing, is that it's all about the shape of the port rather than the surface texture. Work on the shape!

Keep in mind that head porting is really 2nd semester stuff because it's not intuitive. There are people that do nothing but cylinder heads and some of them can really boost the power. Sometimes you're way ahead if you farm some of the work out. Cylinder heads, in my opinion, fall into this category because it's so easy to go backwards.
Be interested in you take on the differences between heads/cams and perhaps inlet manifolds for turbo cars vs n/a Michael?
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Old 11-07-2013, 07:14 AM
  #115  
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Shawn, if you can section some heads, you'd learn a whole lot. Was able to do that with some old Ford 2.3L heads several years ago. Also, to Michael's point, he is absolutely right. There are some exceptions, basically older cast iron heads such as older American V8's. But for anything resembling a modern head (and that includes ours), tread very carefully!
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Old 03-24-2014, 10:06 PM
  #116  
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Default Stock 2.7l head

Hey...since your original intention was a 2.7l head, do you know if the company mentioned (SI) makes valves that will work in stock 944 2.7l heads? I need 3 exhaust valves (40mm, 944 105 418 00) and 1 intake valve (48mm, 944 105 409 03). Looking for options here so I don't have to spend over $700 on 4 valves...

Thanks,
Bob
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Old 03-25-2014, 12:22 AM
  #117  
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Originally Posted by RedPorsche944_27 View Post
Hey...since your original intention was a 2.7l head, do you know if the company mentioned (SI) makes valves that will work in stock 944 2.7l heads? I need 3 exhaust valves (40mm, 944 105 418 00) and 1 intake valve (48mm, 944 105 409 03). Looking for options here so I don't have to spend over $700 on 4 valves...

Thanks,
Bob
Yep, call them.
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Old 03-20-2015, 02:00 PM
  #118  
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Originally Posted by refresh951 View Post
Planning a High Flow Head 2.0, aka Ultra High Flow 8V Head Hoping to have a really great flowing 8V head (yet low cost) ready for the Spring. Who is using 50mm intake valves?
Shawn, bumping this thread for info on 50mm intake valves.

Has anyone run any valves this large? I am looking into doing 50mm valves on my 2.7 head, which with the increased bore size, leaves some room to play.
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Old 03-21-2015, 01:54 AM
  #119  
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https://rennlist.com/forums/928-foru...ld-test-2.html

52 mm intake valve in a 104 mm bore.
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Old 03-21-2015, 07:28 PM
  #120  
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Originally Posted by slate blue View Post
https://rennlist.com/forums/928-foru...ld-test-2.html

52 mm intake valve in a 104 mm bore.
I think this confirms what Jon Milledge has said, no reason to really go more than 48mm on a 104mm bore. I also saw this on my flow bench. I think especially when you can get 48mm valves for $29/each. Just my opinion. The reward past 48mm is minimal at best. The cost goes up dramatically and the valves just get heavier. If you want much more flow than 250cfm then the 16V head starts to really make sense. In my mind the beauty of the 8V head is fairly good performance at a bargin price. If cost is not really a consideration then the 16V head is the way to go.
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