Novice Modified 289 Heads

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RevTheory
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Re: Novice Modified 289 Heads

Post by RevTheory »

Yeah, I see your point now.
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Re: Novice Modified 289 Heads

Post by The Iron Icon »

Look for some more flow results later on today, they will be in .050 increments. You can thank Stan for that.
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Re: Novice Modified 289 Heads

Post by David Vizard »

Here are the correct? graphs with Stans new 0.050 increment graph layout.

These are the stock valves (reshaped) on the stock seats with the throats blended into the seats to leave about a 0.060 wide seat.
AS you can see, graph #1, the flow went up quite a bit on the intake – not so much on the exhaust. But as DV keeps on saying the most useful data is not in the flow numbers but in the other factors I am showing the graphs for.

Ref. graph #2, the CD – the lower than can be achieved CD in the first 0.100 is due to the need for a more efficient seat job. As soon as I can get on the seat and guide machine that is what I will do.
However, the more telling part of the CD curves apparently is what they do after they have hit the 0.25 D lift point. According to DV’s teachings if they don’t climb steeply after the 0.25 mark it is a sure-fire indication that there is most likely not enough port bias in the bowls (might not be enough metal either). There are other signs of port inefficiencies but not room enough to go into details here.
Obviously, the ports got bigger in area when I ground on them. The question now is how did this affect the port velocity?
The third graph down shows this. At low lift the bench showed some loss but a substantial gain at high lift. With curves like this it is hard to tell if robbing Peter to pay Paul has worked out. Fortunately graph #4 showing the port energy settles the question here. The % increase in flow far outweighed the increase in volume and so the port energy goes up. This indicates the heads will be strong performers,

Where too next? Got to get that ex. port up to or at least close to DV’s and Charlies.
Also the seats will get a DV NASCAR seat job as per the late 1990’.
Comments please---

Iron Icon Phil
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Re: Novice Modified 289 Heads

Post by Elroy »

David Vizard wrote: Sat Jul 20, 2019 10:53 am Here are the correct? graphs with Stans new 0.050 increment graph layout.

These are the stock valves (reshaped) on the stock seats with the throats blended into the seats to leave about a 0.060 wide seat.
AS you can see, graph #1, the flow went up quite a bit on the intake – not so much on the exhaust. But as DV keeps on saying the most useful data is not in the flow numbers but in the other factors I am showing the graphs for.

Ref. graph #2, the CD – the lower than can be achieved CD in the first 0.100 is due to the need for a more efficient seat job. As soon as I can get on the seat and guide machine that is what I will do.
However, the more telling part of the CD curves apparently is what they do after they have hit the 0.25 D lift point. According to DV’s teachings if they don’t climb steeply after the 0.25 mark it is a sure-fire indication that there is most likely not enough port bias in the bowls (might not be enough metal either). There are other signs of port inefficiencies but not room enough to go into details here.
Obviously, the ports got bigger in area when I ground on them. The question now is how did this affect the port velocity?
The third graph down shows this. At low lift the bench showed some loss but a substantial gain at high lift. With curves like this it is hard to tell if robbing Peter to pay Paul has worked out. Fortunately graph #4 showing the port energy settles the question here. The % increase in flow far outweighed the increase in volume and so the port energy goes up. This indicates the heads will be strong performers,

Where too next? Got to get that ex. port up to or at least close to DV’s and Charlies.
Also the seats will get a DV NASCAR seat job as per the late 1990’.
Comments please---

Iron Icon Phil
I am assuming DV is short for David Vizard. So is it common on this board to speak of oneself in first person? Or is this possibly someone else posting for him or a glitch. Struck me as funny. Its all good. Anyway. Elroy understands what Elroy read regardless. :lol:
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Re: Novice Modified 289 Heads

Post by PRH »

Is the CD taking the valve job/seat angles into account, or it it strictly based on the theoretical flow of the curtain area?
Or something else altogether?

The reason I mention it is, using the flow numbers posted, and working out the CD for the curtain area....... it doesn’t take a big upward swing doing it that way.

Just casually looking at the flow and CD graph...... why would the CD start showing a big improvement after .350 lift when the port flow is starting to plateau while the valve is being opened more and more?

Looking at the exhaust port, using 147cfm per sq/in of curtain area and a 1.45” diameter valve, I get a CD of .538 @.350 lift(126cfm), and .440 @.500 lift(147cfm).
Last edited by PRH on Sat Jul 20, 2019 2:44 pm, edited 3 times in total.
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Re: Novice Modified 289 Heads

Post by RevTheory »

Phil, I had a situation at David's porting class where I kept working a Vortec port and the damn thing kept nosing over and I wasn't about to let that go. When you simply looked at the mean port velocity, they looked a little slow but something was definitely unhappy. Turns out that there was a local velocity that hit 393 ft/sec at the apex on the short turn side at barely .450 lift. Apparently that kept everyone else unhappy because the port started getting noisy and although the local velocity came back down, the port never recovered.

Sneaking a flowball up there got the port to quiet down and stabilize but David was able to show us that the fix to the problem was counterintuitive to what the flowball was saying. Once we zeroed in on the hot spot and where to actually address it, that local velocity came down a bunch but the mean port velocity went back up and the port remained stable to .800 and apparently that's quite a feat on a Vortec head.

I guess my point here is that I found it quite interesting to see how one local spot can get freaky and drag the whole port down from there on up. I likened it to a bunch of women trying to merge from two lanes into one and stacking the place up for miles, lol.

It would be interesting to velocity probe your head because it's rolling over at less than 270 ft/sec. Yours is gentle as opposed to my Vortec falling off a cliff though so there may be nothing there worth messing with.

These are the Vortec's I did at David's class. Thin line is stock. As you can see, I really didn't gain a damn thing if we're just looking at mean port velocity but, like David said, the other things his program calculates paint a clearer picture. They ended up right at 180cc with a 1.95 cross section at the pinch, 88% throat with a 1.94 intake valve.
Vortec CFM.PNG
Vortec CoD.PNG
Vortec Velocity.PNG
Vortec Port Energy.PNG
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Re: Novice Modified 289 Heads

Post by PRH »

I have the same question about the Vortec results above.

How can you have the CD flat line if there is no gain in flow with the valve being opened more and more?

Same flow from a bigger hole = lower CD.
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Re: Novice Modified 289 Heads

Post by Stan Weiss »

PRH wrote: Sat Jul 20, 2019 2:47 pm I have the same question about the Vortec results above.

How can you have the CD flat line if there is no gain in flow with the valve being opened more and more?

Same flow from a bigger hole = lower CD.
Because after a point the curtain area is not the smallest area and that (smallest) area does not change with valve lift.

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Re: Novice Modified 289 Heads

Post by PRH »

Understood....... so the CD is based on something other than the curtain area.

Throat diameter?
Actually, that wouldn’t make any sense....... since the CD numbers would go up as the valve were opened farther until you reached the area of the throat(assuming the flow went up as the valve opening increased).

Curtain area up to the point where the throat area and curtain are are the same?

What is the program using for cfm per sq/in as the reference for CD?
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Re: Novice Modified 289 Heads

Post by steve cowan »

Rev,
Curious to what happened to all the airspeed on those vortec heads
My 178cc dart heads have same parameters as in valve size, avg CSA, throat etc on the intake side I am talking about.
I don't want to compare flow numbers but from. 200''-.0.400 "mine sneak past and then are the same at upper lifts but my airspeeds are way faster than that,
At the apex of SSR
10"- 255 ft/sec
28"- 360 ft /sec
35"- 455ft/sec
On the floor of the Port before the apex airspeeds are way faster, pushrod pinch is same as apex readings, these are tested at these depressions and not calculated off 10".these heads have been on one of my 383 sbc this year with 70 plus quarter mile passes, I have tested rocker ratio and lash loops, cam timing, tri-y headers and smaller exhaust system, 1 3/4" four into 1 pipes and 3 1/2 exhaust system, airgap intake, single plane intakes and spacers, different shift points at the track and after all this I have come to the conclusion that the pushrod pinch area is to small and is the cork in the induction system and after testing everything else mentioned and only making 1-2 mph difference. I have learned a couple of things this year and this will give me a chance to improve for next year and hopefully make a bit more power.
And I also hope someone will answer Dwayne question on CD as well as I found his comments very interesting and I think important as well :D
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Re: Novice Modified 289 Heads

Post by Stan Weiss »

PRH wrote: Sat Jul 20, 2019 3:18 pm Understood....... so the CD is based on something other than the curtain area.

Throat diameter?
Actually, that wouldn’t make any sense....... since the CD numbers would go up as the valve were opened farther until you reached the area of the throat(assuming the flow went up as the valve opening increased).

Curtain area up to the point where the throat area and curtain are are the same?

PS - After a quick look this looks about right for that option

What is the program using for cfm per sq/in as the reference for CD?
I would have to go in and look at the code to see what I do for that option.

The program uses 146 cfm per sq / in

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Re: Novice Modified 289 Heads

Post by PRH »

I thought that the typical way CD was interpreted was against the curtain area.

I’ve also heard about using the actual valve seat specs to calculate the available area between the valve and the seat at the various lifts, and use that instead of the curtain area as the basis for the theoretical flow potential.......which makes sense to me.
(A valve with a 55* seat lifted .100 creates a smaller path than the same diameter valve with a 30* seat lifted that same .100, and the curtain area method doesn’t take that into account).

So, while I totally understand there will be situations where the curtain area will exceed some point of min csa inside the port....... it still makes sense to me having the curtain area(or better yet, the valve job area) be the reference point for the CD....... since, if you open the valve that far........ the potential to use that area exists.

After all, if the same amount of air is moving past the same valve in the same port at .500 lift and .700 lift...... isn’t the air going a little slower as it passes by the valve through the .700 lift opening?
Last edited by PRH on Sat Jul 20, 2019 4:31 pm, edited 3 times in total.
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Re: Novice Modified 289 Heads

Post by RevTheory »

Steve, I think on average, my airspeeds along the floor are probably closer to what you've seen on your Darts. That's why I mentioned probing for local velocities rather than relying on the program to give you the mean velocity.

Now what I didn't get a chance to do (dammit!) was probe the port again after we got the problem fixed. There were two other guys at the class that had very specific porting issues to get sorted out on their actual race engine programs as opposed to me just trying to learn some stuff for the hell of it.

I don't know if these attachments will be useful to you at all or if they're even readable. What I did find interesting is being able to watch the air try to hug the pushrod side until the valve opened up enough for the bulk of the air to start transitioning over to the common wall side: at least that's what I think I'm looking at.

Note! Don't blame David for my silly charts. He took a class attendee to Terry's place in Virginia to dyno an engine and this is what happens when I'm left alone :lol:

Shoot, these darn pics are right-side-up in my folders. Maybe they'll straighten up if you click on them.
IMG_0762.JPG
IMG_0760.JPG
IMG_0761.JPG
Edit: Ugh. I guess no on the pics. Sorry fellas.
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Re: Novice Modified 289 Heads

Post by Carnut1 »

Rev, any word on which heads, engines DV is testing?
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Re: Novice Modified 289 Heads

Post by GARY C »

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