to fast over SSR

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PRH
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Re: to fast over SSR

Post by PRH » Mon Jul 23, 2018 1:33 pm

83% seems kinda low on the ex throat size to me.

It looks like the entry from the chamber into the bowl is decent, so “if it were me” I’d open the bowl diameter some and work on the short turn profile.

Have you tested the ex port without the tube?
I’m just curious as to how much affect it has on a small port like that .
Somewhat handy with a die grinder.

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Re: to fast over SSR

Post by steve cowan » Mon Jul 23, 2018 3:56 pm

PRH wrote:
Mon Jul 23, 2018 1:33 pm
83% seems kinda low on the ex throat size to me.

It looks like the entry from the chamber into the bowl is decent, so “if it were me” I’d open the bowl diameter some and work on the short turn profile.

Have you tested the ex port without the tube?
I’m just curious as to how much affect it has on a small port like that .
PRH thanks for the response,
I remeasured throat it's 83 %, I worked it to 86%, I am worried about going bigger as it is at seat ring base now, I flowed with and without pipe and it's still spitting around 300"lift, I had a look with pitot with no pipe.
0 flow on the floor, 360 ft/sec at the centre of the Port at the apex
Sides of Port around 320-340 ft/sec
Around the stem of the valve at the bowl area seems fast at 360-370, I can't get a accurate reading as the velocity reading as it's going a little crazy probably because of the turbulence,
I have a under cut stem valve I was going to try and then look at the SSR to try and slow air down a bit.
I am thinking around 280-290 ft/sec as a average port speed, but I am only guessing on that. :D
steve c

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Re: to fast over SSR

Post by PRH » Mon Jul 23, 2018 4:18 pm

Clarify for me what you mean by “spitting”.
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Re: to fast over SSR

Post by PRH » Mon Jul 23, 2018 6:22 pm

One other thought.......

If the back side of the bowl falls away from the short turn side, down below the seat, to where it’s almost forming a little “pocket”(opposite of the port exit)...... I’ve never found that shape to give me “good” flow numbers, and they usually sound pretty raspy as well.

The deeper that pocket is, the worse they flow..... for me anyway.
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Re: to fast over SSR

Post by Steve Haaf » Mon Jul 23, 2018 7:08 pm

Steve, this may help you,Darin Morgan posted this in 2005. My personal opinion and from what I have learned about exhaust ports I have to say that small super fast exhaust ports make more power over larger high flowing exhaust ports except in the case of full exhaust systems such as Nextel cup engines. For some reason they like a slightly larger exhaust port but no where even close to what I would call large. Large and Small are ambiguous. In my book anything over about 110% of the valve area is large and anything under 105% of the valve area is very small but the exit velocity seems to play a role here as well. I try to adhere to the 105-108% in our pro Stock engines and it seems that I am not alone in my theory because many of the top notch heads I have seen are about the same or within about 2%. Another very big thing to consider in the tuning of exhaust ports is there sound or should I say the lack of sound. How smooth an exhaust port sounds and how quietly it can move the air are both very serious factors to consider. As the valve opens the sound of the ports should smooth up and get increasingly silent. The loudest portion of the exhaust flow on the bench is from .200 to .400 after that they should go increasingly silent with every lift increment. I have had exhaust ports that actually cracked and popped like fire crackers! With a little seat blending and chamber work I managed to smooth up the flow, gained a measly 2 cfm average and gained 26 horsepower and it still was not correct because the port was to big. The hardest thing I do is try and fix exhaust ports that are screwed up. Its much easier to fix intake ports!
Like an intake port, an exhaust port can be made to flow a great deal of air, Just make it big.

Some rules I live by.

(1) Exit area = 105-110 % of the valve.

(2) Exit air speed at a minimum of 300 and a max of 330 ft/sec mean.

(3) Smooth silent flow by at least .400 lift and absolutely by .500 lift.



On another note, I am not sold on the theory that the flow in the exhaust port goes Sonic. Anyone here care to prove this theory?

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Re: to fast over SSR

Post by steve cowan » Mon Jul 23, 2018 8:49 pm

Steve Haaf wrote:
Mon Jul 23, 2018 7:08 pm
Steve, this may help you,Darin Morgan posted this in 2005. My personal opinion and from what I have learned about exhaust ports I have to say that small super fast exhaust ports make more power over larger high flowing exhaust ports except in the case of full exhaust systems such as Nextel cup engines. For some reason they like a slightly larger exhaust port but no where even close to what I would call large. Large and Small are ambiguous. In my book anything over about 110% of the valve area is large and anything under 105% of the valve area is very small but the exit velocity seems to play a role here as well. I try to adhere to the 105-108% in our pro Stock engines and it seems that I am not alone in my theory because many of the top notch heads I have seen are about the same or within about 2%. Another very big thing to consider in the tuning of exhaust ports is there sound or should I say the lack of sound. How smooth an exhaust port sounds and how quietly it can move the air are both very serious factors to consider. As the valve opens the sound of the ports should smooth up and get increasingly silent. The loudest portion of the exhaust flow on the bench is from .200 to .400 after that they should go increasingly silent with every lift increment. I have had exhaust ports that actually cracked and popped like fire crackers! With a little seat blending and chamber work I managed to smooth up the flow, gained a measly 2 cfm average and gained 26 horsepower and it still was not correct because the port was to big. The hardest thing I do is try and fix exhaust ports that are screwed up. Its much easier to fix intake ports!
Like an intake port, an exhaust port can be made to flow a great deal of air, Just make it big.

Some rules I live by.

(1) Exit area = 105-110 % of the valve.

(2) Exit air speed at a minimum of 300 and a max of 330 ft/sec mean.

(3) Smooth silent flow by at least .400 lift and absolutely by .500 lift.



On another note, I am not sold on the theory that the flow in the exhaust port goes Sonic. Anyone here care to prove this theory?
Thanks Steve
I actually read that same post on the weekend, got some thinking to do,
Going to do some measurements tonight, try a different valve, play with some clay, and if all fails, work the SSR as I think that's the area needs work, at the moment short turn is untouched
steve c

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Re: to fast over SSR

Post by steve cowan » Tue Jul 24, 2018 3:29 am

PRH wrote:
Mon Jul 23, 2018 4:18 pm
Clarify for me what you mean by “spitting”.
Popping, just sounds like unstable air I spose you can say,
I tried the undercut stem valve and turbulence reduced back to 200" and 300" lift
Can the SSR at low to mid lift have a big influence, once lift gets to 400" lift and above the exhaust becomes quiet and no popping at all at any depression
steve c

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Re: to fast over SSR

Post by Carnut1 » Tue Jul 24, 2018 6:59 am

steve cowan wrote:
Mon Jul 23, 2018 3:56 pm
PRH wrote:
Mon Jul 23, 2018 1:33 pm
83% seems kinda low on the ex throat size to me.

It looks like the entry from the chamber into the bowl is decent, so “if it were me” I’d open the bowl diameter some and work on the short turn profile.

Have you tested the ex port without the tube?
I’m just curious as to how much affect it has on a small port like that .

PRH thanks for the response,
I remeasured throat it's 83 %, I worked it to 86%, I am worried about going bigger as it is at seat ring base now, I flowed with and without pipe and it's still spitting around 300"lift, I had a look with pitot with no pipe.
0 flow on the floor, 360 ft/sec at the centre of the Port at the apex
Sides of Port around 320-340 ft/sec
Around the stem of the valve at the bowl area seems fast at 360-370, I can't get a accurate reading as the velocity reading as it's going a little crazy probably because of the turbulence,
I have a under cut stem valve I was going to try and then look at the SSR to try and slow air down a bit.
I am thinking around 280-290 ft/sec as a average port speed, but I am only guessing on that. :D

Steve, is this with a backcut valve? Try without the backcut and a radius face to see what happens to the turbulence and flow curve. Thanks, Charlie
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Re: to fast over SSR

Post by steve cowan » Tue Jul 24, 2018 9:04 pm

Hi Charlie,
No backcut on the valve,
I don't really know what radius face means,
Is it blending the valve seat in or radius on top off margin on valve, sorry for the confusion on my part
steve c

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Re: to fast over SSR

Post by Ron E » Tue Jul 24, 2018 9:39 pm

PRH wrote:
Mon Jul 23, 2018 6:22 pm
One other thought.......

If the back side of the bowl falls away from the short turn side, down below the seat, to where it’s almost forming a little “pocket”(opposite of the port exit)...... I’ve never found that shape to give me “good” flow numbers, and they usually sound pretty raspy as well.

The deeper that pocket is, the worse they flow..... for me anyway.
Keep this in mind as well. Its good advice.

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Re: to fast over SSR

Post by pcnsd » Wed Jul 25, 2018 1:00 am

steve cowan wrote:
Tue Jul 24, 2018 3:29 am
PRH wrote:
Mon Jul 23, 2018 4:18 pm
Clarify for me what you mean by “spitting”.
Popping, just sounds like unstable air I spose you can say,
I tried the undercut stem valve and turbulence reduced back to 200" and 300" lift
Can the SSR at low to mid lift have a big influence, once lift gets to 400" lift and above the exhaust becomes quiet and no popping at all at any depression
I have a popping exhaust port at .2"-.3" lift. I can measure reverse flow going past the valve into the chamber along the center of the SSR at those lifts. It is worst at .2" I don't have a solution yet (just found it tonight), but I wonder if you might have the same phenomena.
- Paul

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Re: to fast over SSR

Post by steve cowan » Wed Jul 25, 2018 5:17 am

steve cowan wrote:
Tue Jul 24, 2018 9:04 pm
Hi Charlie,
No backcut on the valve,
I don't really know what radius face means,
Is it blending the valve seat in or radius on top off margin on valve, sorry for the confusion on my part
[attachment=0]dart 165cc exhaust data 001.JPG[/attachment

Charlie,
found this in my chevy heads book,
the Manley valves are standard,good suggestion of the radius face and maybe worth trying a 30 deg backcut on the exhaust valve as well as a separate test.
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steve c

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Re: to fast over SSR

Post by steve cowan » Wed Jul 25, 2018 5:37 am

pcnsd wrote:
Wed Jul 25, 2018 1:00 am
steve cowan wrote:
Tue Jul 24, 2018 3:29 am
PRH wrote:
Mon Jul 23, 2018 4:18 pm
Clarify for me what you mean by “spitting”.
Popping, just sounds like unstable air I spose you can say,
I tried the undercut stem valve and turbulence reduced back to 200" and 300" lift
Can the SSR at low to mid lift have a big influence, once lift gets to 400" lift and above the exhaust becomes quiet and no popping at all at any depression
I have a popping exhaust port at .2"-.3" lift. I can measure reverse flow going past the valve into the chamber along the center of the SSR at those lifts. It is worst at .2" I don't have a solution yet (just found it tonight), but I wonder if you might have the same phenomena.
Paul,
sounds like the same deal as i am having,i still think its the SSR as the airspeed needs to come down to around 300 ft/sec at the short turn,( my research )
i have not forgotten what PHR and RON E have mentioned,i am just trying to tick all the boxes before i pick the grinder up again,
i have only checked airspeeds at full lift as i ran out of time the other night,going to have another look tomorrow night,i want to document the unstable air at the 200''-300'' lift range with the pitot.
i found it picked up a bit of CFM with the undercut valve stem but i am not reading into that to much,the air was smoother around the 300''-400'' lift range so believe the valve did make a slight difference on the bench.
from what i can see from the pitot and flow balls the air flow out of the chamber and past the valve shoots towards the roof of the port,there is no airflow on the floor and 0 air until the pitot is half way up the port,in my head i am thinking SSR but there is no air there to speak of so..................
dart 165cc exhaust data 002.JPG
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steve c

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Re: to fast over SSR

Post by Carnut1 » Wed Jul 25, 2018 6:52 am

steve cowan wrote:
Tue Jul 24, 2018 9:04 pm
Hi Charlie,
No backcut on the valve,
I don't really know what radius face means,
Is it blending the valve seat in or radius on top off margin on valve, sorry for the confusion on my part
Face is the part of the valve that shows in the chamber when the valve is seated. A radius on the margin (the edge facing out from chamber) may change the flow enough to eliminate that noise. It is sometimes worth a flow increase. Thanks, Charlie
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Re: to fast over SSR

Post by mag2555 » Wed Jul 25, 2018 8:11 am

That gargling that your hearing at low lift is caused by they same thing where it's heard at low lift points ( under .350" ) in Intake ports, that being its the flow transition point where the air is able to follow the path of least resistance thru the port and then having to follow the contours of the port at higher lifts and flow rates.

At higher lifts above .400" that noise is a different story!

The more tightly on 23 degree heads that the Exh port is bent / curved around valve guide area the better the low lift flow will be , the taller and more gentle this curve is the better the high lift flow will be.

This in conjunction with the arc of the SSR radius and width of the SSR up to to the apex of the floor plays a big part in how close the air speed between these two can get , but once again too gentle of a arc and or too much height expansion between the roof and the SSR/ floor and your low lift numbers go south real fast!

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