Airflow over small SSR and low apex height

[WPH]

I just started with a head which has about 0.6-0.7" apex height and a smallish SSR. I widened the port floor and laid back the profile.
I gained some flow but when I blended the cuts to port walls and bowl the flow backed off. This made me wonder what went wrong.
The port flow seems to be faster at the floor than the roof. I tested the the flow paths with a string and the flow keeps closer to the
floor than the roof. If I put a blob of plasticine to port entrance floor the flow picks up better than ever.

The air acts like it's going over a higher apex and larger SSR and the test string attaches closer to port roof.
I wonder which way to go next, more port volume around the guide? In these areas the flow seems to be kind of "dead".

[blaktopr]

I have the same problem on one head with the apex at that same kind of height. Clearing the area of the guide boss "worm hump" before the guide with a good radius at the guide boss did not help me. Plus I tried on the chamber side to slightly lower and blend the ssr into the seat and lost a little. That is on my head. And I can't seem to keep the air attached over that short ssr when trying to keep the min csa at the throat and not the pinch.

Chris.

[WPH]

Try the "blob", I was amazed about the flow boost it gave. I'll just have to figure out how to get the same kind of results without it.
If I could fill the port floor I'd try that but it is out of the question at the moment.

[blaktopr]

[Otto]

the next thing i would check is installing the manifold and does in effect change the flow i know in my applications the manifold makes a major effect on air entering the port and changes the air colume profile just a thought

[WPH]

Unfortunately I don't have a manifold to test with, I'll have to ask for it from the guy who's head this is. I think I've seen a picture of a Ford V8 head which had a wedge plastered to the entrance of the port floor and the roof of the port was ground higher. Maybe to fix a problem like this?

If anyone has managed to fix a problem like this without filling the port floor I'd be very interested to hear how you managed to do it.
I'll try to get a couple of photos of the SSR and the apex to show how it looks like at the moment compared to stock.

Pekka

[106-1194218389]

I raised the roof at the manifold side and in a ways to help the angle of attack. But as has been suggested get the intake before you make any decision. My port was still a little rough flowing until I installed the intake, Then the port went dead smooth.

Two reasons I think this happened is the total air flow dropped by 40 cfm so velocity also had to drop. The second reason is it seemed to help direct the air. The manifold I am using is an Edelbrock EPS Performer.

Do you have a pitot and probed the port velocity? In my SBC it is faster over the floor of the SSR. Raising the roof helped a little. With these types of heads you will not get totally away from that. I probed my port and found that the average velocity about .75" before the apex towards the intake mating surface was a little fast. After I did my port mold and measured there it was indeed still a little small.

John

[blaktopr]

I checked bolting a single plane intake to mine. Flow did drop but did not cure the problem I have. The flow curve does not crash. They continue upward. Also, I did not mention this before, but in this condition I call "turbulent", the speeds at the curtain do show a little faster at some points. Probing the whole port, and today with the intake on, shows acceptable speeds throughout the tract, fastest at parts of the curtain, just a tad slower at the pinch, and checked up to the plenum. It looks good on paper but I still don't like the "turbulent situation." Flow slows but good to keep velocities in check. To see this, is where the wet tests help. liquid goes out the long side, goes around the chamber, starts to collect on the pad under the ssr, gets drawn into the low pressure area at the exit next to the cylinder wall where speeds are highest, and gets sprayed down the cylinder wall under that area. To furthur test whether or not this fluid is rounding the ssr at that side or that it is being drawn from the chamber after it exits the valve on the long side, I introduce the liquid at the long side curtain area and furthur toward the chamber and the pattern looks the same. During this test, NO liquid is in the runner. It is the same with or without the intake. These are my tests and I am not saying this holds true with everyone's port.

Chris.

[WPH]

Manifold testing done. Port dia is now enlarged to what I think it should be when installed to a real engine. Didn't check the port speeds yet since I have to to finish the guides and do the seats. I have managed to get some clues what other porters have done with this head and I've come to a conclusion that this head is pretty challencing to get some good numbers. One porter suggested that I shouldn't get stuck with the flow figures, just check the speeds and max out out the SSR and apex unless you're doing some serious port floor filling. not to mention the hole I managed to do on the cyl#4 port roof due to some porous casting close to spring seat area. Any ideas to make a good repair to a hole which goes to oil return passage? Has anyone done repairs with aluminum filled "bondo" (polyester resin). Does it hold/withstand the typical temperatures in cyl head oil return passage area? No pressure involved, just a free flow of oil to block passage.

[106-1194218389]

we used some two part devcon. after it was cured and shaped we paint it with rustoleum damp proof red primer to seal it from the oil and ran it for a long time with no problem. This was in a push rod pinch area of a smal block Chevy that we totally removed and built it back with screen that we devconed in place and built a few layers up on it.

John

[blaktopr]

Pekka. Try a test without the valve, to see the effects the valve has on the flow quality and amount. May be another place to look rather than the port itself. There are ports that the valve helps or it hurts.
Nothing new. I am also finding when reducing the pinch area, that even though the speeds are down, the volume goes up, still sometimes causing a problem over the ssr.

Chris.

[WPH]

Valve helps this port to a certain degree(mildly ported). With the finished/more advanced port I'm not sure. Did a port floor fill with plasticine and the flow gets such a big boost that it's hard to come by any other way. I have to do some more tests, modified the inlet valves and guides last night+enlarged the seat ring inside dia.

[WPH]

Straight five hours on the flowbench and some progress. The port needs a fix but not sure what causes it. I'm thinking of a valve shrouding caused by the chamber wall and the bore. The fix I found was rather unusual to my experience but it works till a certain valve lift. After that the flow goes violently turbulent and drops off.

I played with some plasticine and built some height to apex. Next thing was to find a the best angle and radius to SSR. Then I started to lower the apex and tilt the angle approaching the valve backwards on the chamber wall side of the port. The shape is a bit rough at the moment but a definite improvement to flow. I didn't have time to check the lift when the turbulence hits the port since it got kinda late, almost midnight. Talking about addiction....

I'll try to post a pic tomorrow to show what I've done so far.

[WPH]

Here's a rough picture of the cross section at apex. I've recorded the port speeds I measured for reference.
So far the head flows 114.5 CFM @ 10" with a 44mm intake valve. I estimate the CA to be 1.6-1.63 square inches
but I'll have to check it again. Lower part of the apex is at chamber wall/bore side of port.



Flow stays stable till 13-13.5 mm of lift. This is without the backcut to the valve. With the backcut I get more flow
through whole curve but it drops off totally at 12mm or even lower. Maximum flow number stays about the same.
This port flows better with valve than w/o both in stock and modified. Shape is completely round as stock but the
angled floor/apex is due to light port fill I did to experiment with this head. So far only things done to this port was
raising roof slightly and smoothing the bowl. Valve throat is 90% of the valve diameter.

One of my tests included filling the roof back a little but the flow dropped. Flow was more evenly distributed throughout
the whole pinch and the highest apex speed went up at the same time.

[WPH]

Intake flow data and some pictures of the actual head:

lift@mm CFM@10" , 44mm valve
2.2 28.9
4.4 58.5
6.6 83.6
8.8 102.1
11.0 112.3
13.2 118.8
15.4 121.9