port shape?

bc · Post by bc » Fri Oct 21, 2005 11:02 am

Im wondering which style port would flow more and why. I have a head that I have raised the intake roof as high as it can go and got the cross section set the way I want. I started think about moving the pushrod and raising the floor up to keep the same cross section but would doing that show enough of an improvement to justify the cost of offset shaft rockers. So basically what would be the better port shape a tall narrow port or port that the roof is the same height as the first one but wider and the floor raised (I could raise the flow about .400 and widen the port by about .200 and still have about the same cross sectional area). And do you guys think that there would be enough of a performance difference to though the extra work and cost? Thanks

dbusch · Post by **dbusch** » Fri Oct 21, 2005 12:00 pm

good question. i look forward to the replies. My opinion would be the higher floor port would be better. It would concentrate the airflow into the center and roof of the port more vs. the tall narrow port that would have more air down low. The taller floor should allow the short turn to be more gradual in its turn, assuming the apex is back far enough. This means less turbulence and more power. All the NASCAR heads are short and wide, arent they?

2T4T · Post by **2T4T** » Fri Oct 21, 2005 4:53 pm

Hello,
Korean SAE paper :
2004-01-0998 : A Correlation Between Re-Defined Design Parameters and Flow Coefficients of SI Engine Intake Ports
R.

bc · Post by bc » Fri Oct 21, 2005 8:36 pm

Anyway you can post the SAE paper for those of us that dont have access to it?

shawn · Post by **shawn** » Fri Oct 21, 2005 8:50 pm

I think that might be a copywrite infringement. You can download it from the SAE website for $12.00. Here's the link-

http://www.sae.org/servlets/productDeta ... 04-01-0998

shawn

Joe Mendelis · Post by **Joe Mendelis** » Sat Oct 22, 2005 12:33 am

dbusch wrote: All the NASCAR heads are short and wide, arent they?

I've only seen older SB2 heads that look like that. None of the new ones do. (even plate)

Post by **gofaster** » Sat Oct 22, 2005 2:28 am

Try filling the floor with clay to approximately the shape you think will work and put it back on the flowbench.

If you don't have a flowbench, ffill it with epoxy and grind it to the shape you think will work and run it. You can always add epoxy or grind it back out later if you need to make more changes.

hotrod · Post by **hotrod** » Sat Oct 22, 2005 4:01 am

NACA did some work in 1946 on a low drag inlet elbow for the compressor inlets on WWII aircraft engines. The inlet they designed was called a "high aspect ratio inlet elbow" .

http://naca.central.cranfield.ac.uk/rep ... n-1148.pdf

The short version was -- it had a constant area but at the bend where it turned nearly 90 Deg they flattened the elbow so it was much narrower in the direction of the radius of the turn and several times wider perpendicular to the radius of the bend. This significantly reduced shear in the air flow as it tried to make the turn.

The inside wall (comparable to the short side radius) was very early the same curvature as the long side of the turn. About a 3:1 or 4:1 aspect ratio as I remember.

I have thought the concept might be useful in an intake port if you could figure out packaging and still get a wide flat port shape inside the casting along with the cooling passages etc.

Larry