Re: Ported Dart 215's with port energy discussion 3.0

[GARY C]

IOW, it seems counterproductive to worry about fancy shapes when the port floor and apex speeds are still too fast.

The fin should taper to nothing before the apex so the air speed slows just before the apex to make the turn.

[Carnut1]

20180403_183805.jpg Hand drawn ssr apex airspeeds. Right side is the cylinder wall side. Input welcome. Taken at .7" lift. 304 ft/sec center pinch airspeed. Thanks, Charlie

That looks like ass! No, really.. it does.

Sorry.. the juvenile just sneaks out uncontrollably sometimes.

What about the pinches floor speeds?

So I have another question. With such high apex speeds right at that vane.. why would you not gain flow by removing it altogether and reducing center apex speeds.. and potentially allowing more air to make it over the center of the short side.

IOW, it seems counterproductive to worry about fancy shapes when the port floor and apex speeds are still too fast. I'd imagine vanes would be best used when the available cross section was sufficient enough to not be affected by it(the vanes port volume displacement)and create those higher speeds. Just seems to me that finding flow in that area of the curtain is what we work so hard for in the first place, especially on a higher degree head like the sbc.

Dunno.. maybe the wet flow improvement trumps more flow in that area of the valve curtain?

Greg, now if the apex speeds are too high but better organized does it really matter? Apex air speed increased to about 440 ft/sec at 35" depression at 360 cfm.

[groberts101]

Greg, now if the apex speeds are too high but better organized does it really matter? Apex air speed increased to about 440 ft/sec at 35" depression at 360 cfm.

I guess within those testing parameters it would be a definite.. NO. Testing at the typically used lower depressions within or slightly beyond your cams intended lift range would allow that port to easily pass the mustard.

Plus that engine will never come close to needing that kind of flow potential so my gut would tell me that port is already on the large side for your application anyways.

Was just trying to wrap my head around your last posted results/diagram was all. Good work.. carry on and I'll try to keep my big mouth shut for now. Lol

Take care and good luck with it,

Greg

[Carnut1]

Greg, now if the apex speeds are too high but better organized does it really matter? Apex air speed increased to about 440 ft/sec at 35" depression at 360 cfm.

I guess within those testing parameters it would be a definite.. NO. Testing at the typically used lower depressions within or slightly beyond your cams intended lift range would allow that port to easily pass the mustard.

Plus that engine will never come close to needing that kind of flow potential so my gut would tell me that port is already on the large side for your application anyways.

Was just trying to wrap my head around your last posted results/diagram was all. Good work.. carry on and I'll try to keep my big mouth shut for now. Lol

Take care and good luck with it,

Greg

Not trying to keep your mouth shut! I appreciate your input. I don't know it all so I ask questions about the airspeed. Thanks, Charlie

[randy331]

it seems counterproductive to worry about fancy shapes when the port floor and apex speeds are still too fast.

So,... when do we trade on thing for another ?

What other negetives do we accept to have lower st speeds?
Just add area to the st till speed is low enough ?
How low is low enough ?
How low is low enough vs what to get it lowered?
If we have to, we just make it flow less just to get st speeds down ?

How do we decide what else we'll do to achieve lower st speeds ?

And, the same for everything else we do to heads ?
When do we trade one thing for another?
When do we add area at the pushrod when we know it won't flow more when we make it bigger ?

How do we decide what we see on the flow bench will be good for power in the application we are doing the heads for ?

Randy

[GARY C]

it seems counterproductive to worry about fancy shapes when the port floor and apex speeds are still too fast.

So,... when do we trade on thing for another ?

What other negetives do we accept to have lower st speeds?
Just add area to the st till speed is low enough ?
How low is low enough ?
How low is low enough vs what to get it lowered?
If we have to, we just make it flow less just to get st speeds down ?

How do we decide what else we'll do to achieve lower st speeds ?

And, the same for everything else we do to heads ?
When do we trade one thing for another?
When do we add area at the pushrod when we know it won't flow more when we make it bigger ?

How do we decide what we see on the flow bench will be good for power in the application we are doing the heads for ?

Randy

My on track testing showed a basic port job to be good for about 4 tenths of a second beyond that there was no noticeable change until I got to too big and started experiencing shift recovery issues, it was more pronounced when i put the heads, intake and cam on a 76" smaller short block, it's kind of scary when running a 300 horse nitrous system shifting at 7600 and there is a noticeable bog.

[groberts101]

it seems counterproductive to worry about fancy shapes when the port floor and apex speeds are still too fast.

So,... when do we trade on thing for another ?

Considering short turns are the major achilles for most bent port designs we tend to work on?.. I'd tend to lean towards improving the short turns dry flow characteristics on a bench before focusing strictly on improving wet flow charactirstics for which I can only theorize about without the proper tools to even test or see it? Basically, if the dry flow is having known issues making the turn?.. then it sure seems a safe bet to assume a much heavier fuel laden mass probably won't make it around the turn any better? Otherwise. why use a bench or pitot readings in the first place if they have no real life merit on a running engine?

What other negetives do we accept to have lower st speeds?

Not sure, but maybe increased reversional tendencies?.. and even potential pressure recovery issues on the chamber side of things?

Just add area to the st till speed is low enough ?

Seems like an odd question considering the overall design flaw of a bent port.. but if all the other known tricks have been expended at that point?.. probably yes?

How low is low enough ?

When speed gradients have equalized across that area of the ports cross section, net flow gain has not completely stalled out and possibly gained more cfm which typically indicates that portion of the valves curtain area has become larger and more filled in?

How low is low enough vs what to get it lowered?

See above?

If we have to, we just make it flow less just to get st speeds down ?

I don't fully understand the question because at face value it seems rather silly.. but generally speaking?.. I rarely ever have a port actually flow less cfm because I tend to sneak up on the shape and overall size as if I'm tuning a carb. Small and somewhat separated changes at a time. Now, talking from a C/D perspective?.. if the port cross section has been enlarged and flow plateaus out or only increases a very small amount?.. I'd be inclined to think the law of diminishing returns has kicked in and that area is likely sufficient enough for the task at hand or other areas of the port need to be revisited to see what the hold up is.

How do we decide what else we'll do to achieve lower st speeds ?

Study and test upstream obstacles that may be adding insult to injury for other downstream weaknesses? Utilize empirical data gained from firsthand experience or maybe even utilize published results and testing data from reputable sources?

And, the same for everything else we do to heads ?

Probably fall back to the same answer to your previous question/s?

When do we trade one thing for another?

Much tougher one to answer based on my more limited experience.. but maybe that's much more application specific/dependent? Maybe piston speed/flow/power requirement related?

When do we add area at the pushrod when we know it won't flow more when we make it bigger ?

To potentially help relieve upstream speed related issues that could cause larger or harder to mitigate short turn issues further downstream? Or to better equalize.. maybe even improve turn related issues from the manifold exits?

How do we decide what we see on the flow bench will be good for power in the application we are doing the heads for ?

Empirical data gained form firsthand personal experience, like straighter smaller ports can potentially flow more mass at higher speeds than slightly larger bent ports, then look at hundreds, even thousands of peer reviewed data points and testing results gained and shared by others with much more proven experience and larger resources to provide those referenced and proven results? Pick similar applications and reference those specific results to get closer to any particular bullseye? IE: bigger ports for bigger motors.. smaller ports for smaller motors.. rpm range.. power output..engine size?.. etc.. etc.. etc?


Randy

SEE ALL MY ANSWERS ABOVE LISTED IN RED WITHIN THE BODY OF YOUR QUOTE.

Maybe you were just making a rhetorical point?.. or being facetious?.. but thanks for the test, Randy. Now my brain hurts from thinking about all the various possibilities and physics involved with trying to figure this stuff out. Now please show your master tests answer sheet so I can actually learn something from everything I got wrong in my above response! Hopefully you don't dock me too many points for the "see above" time cheats!

[user-9274568]

If you want to see what type of airspeeds will work on the apex of a short side, port a set of competitive Super Stock heads. Because they are crazy fast.

You can get the SSR too low.

I want the speed the same straight across.

You set up the port properly and it can handle the apex speeds.

The floor at the apex is more important, IMO, than any secondary choke (pushrod pinch).

PS. I was on a 5 day block. So play nice.

[Carnut1]

If you want to see what type of airspeeds will work on the apex of a short side, port a set of competitive Super Stock heads. Because they are crazy fast.

You can get the SSR too low.

I want the speed the same straight across.

You set up the port properly and it can handle the apex speeds.

The floor at the apex is more important, IMO, than any secondary choke (pushrod pinch).

PS. I was on a 5 day block. So play nice.

Since I decided to try this design I can't get the air speed the same across the ssr which makes sense to me but I have modified the ssr so it has nearly mirror speeds on either side of the fin. I think it will work well. Thanks, Charlie

[randy331]

My on track testing showed a basic port job to be good for about 4 tenths of a second beyond that there was no noticeable change until I got to too big and started experiencing shift recovery issues, it was more pronounced when i put the heads, intake and cam on a 76" smaller short block, it's kind of scary when running a 300 horse nitrous system shifting at 7600 and there is a noticeable bog.

Did you change cam to match the new flowZZZ each time you worked on the heads ?

Maybe it needed a different ICL or LSA, or 1-2 deg duration change with each change to the heads ?

Maybe that's why you gained 4 tenths, cause the flowZ better matched your cam ??


Randy

[GARY C]

My on track testing showed a basic port job to be good for about 4 tenths of a second beyond that there was no noticeable change until I got to too big and started experiencing shift recovery issues, it was more pronounced when i put the heads, intake and cam on a 76" smaller short block, it's kind of scary when running a 300 horse nitrous system shifting at 7600 and there is a noticeable bog.

Did you change cam to match the new flowZZZ each time you worked on the heads ?

Maybe it needed a different ICL or LSA, or 1-2 deg duration change with each change to the heads ?

Maybe that's why you gained 4 tenths, cause the flowZ better matched your cam ??


Randy

Don't be a flow-b
Actually the engine I bought used had a heavily ported bowtie iron head and a 259/267 @.050 on a 106 installed at a 100 icl when I got it, later I changed it to a dart pro 1 230 head with a 273/286 @.050 on a 110 and the car ran the same et, I chose the cam myself after being spected 4 different cams from Lunati ranging from what I had to more than i chose, i found it close enough later when I ran it on cam master but it was to big for the rpm I was running as were the heads, Darts flow #'s which were 21 cfm higher than what they actually flowed, Darts # 301 cfm, Flow bench # 280 cfm, after porting # 317 cfm it picked up 4tenths, maybe more but that is a conservative # and it wasn't on the same day. The drastic cam change was trying to reduce 230psi cranking pressure because i was running nitrous... it did not lower it as much as I thought it would but at this point it had lived 3 years so I stayed with what I had. Not that it was the best combo but it's what i had to play with.

This was the first race car I ever built and the first real "race" engine, so I would probably do things different now if I was going to race anymore.

[Carnut1]

20180412_093357.jpg

Interesting pic of a roughed out intake flowing about 316cfm at .7" lift. Input welcome.

[user-17438]

20180412_093357.jpg Interesting pic of a roughed out intake flowing about 316cfm at .7" lift. Input welcome.

here is some input, do you see where your radius plate has tighter corner radius than your port. Use some clay and smooth that out in the corners and blend it to the entry.

[Carnut1]

20180412_093357.jpg Interesting pic of a roughed out intake flowing about 316cfm at .7" lift. Input welcome.

here is some input, do you see where your radius plate has tighter corner radius than your port. Use some clay and smooth that out in the corners and blend it to the entry.

It is worth a few cfm. That was some string testing after the port rough out. When I finesse them they will actually be a touch larger than the 1206 gasket. Thanks, Charlie

[Carnut1]

Resized_20180414_200544.jpeg

Having trouble getting a decent pic. I am thinking this is about the final bowl shape I will make the rest. Any input to help someone with no experience? Thanks, Charlie