Port velocities

[106-1194218389]

Thanks Larry for posting the picture here. You also reminded me to take back any bad comments I have made against my Dart heads. They were the 180 CC Iron Eagle and are advertised as "torque" heads. For what they were designed for they were probably fine. Low speed street torque heads. I did not buy the correct heads for my application. Not Dart's fault but mine for not having my eyes open when I bought heads. This is a lesson, if you are buying new heads make sure you buy for your application. I am going to turn the engine to 6500 rpm and ET bracket race it. With Larry's help I am making these heads work. There seems to be plenty of cast iron to get me there. ONce again thanks Larry M.

John

[larrycavan]

Here's the photos..

Currently: With Carb Mounted
96 CFM/SQ.IN @ .500 lift
158CFM@28

At .420 lift [cam = .425]
265 FPS, dead down middle of runner, half way between port entrance and SSR.
148CFM.

SSR @ 335 FPS dead middle.

Actual -NOT- converted up numbers.

Getting a good photo of the SSR isn't easy. Not much height to it.



Edited By larrycavan on 1207094715

[larrycavan]

another

[106-1194218389]

Nice looking port larry.
I just flowed my Dart head again. I had laid back the SSR and took a little off the apex as mention in my last post on this. I had gained flow from .500" up. I did see turbulance from .500 up and can be seen I think in the velocity readings. My camshaft will have .510 lift. I took velocity readings at three different lifts. .400, .450 and .500 listed below: once again reading are top to bottom, pushrod on left and divider wall on right.
.400" lift
pushrod SSR
329 313 297 248 226 248
329 320 293 286 290 290
312 286 248 365 365 365

.450" lift
pushrod SSR
358 335 320 293 202 248
358 329 329 297 286 297
329 295 286 378 378 359

.500" lift
pushrod SSR
386 365 335 293 248 286
392 358 335 303 320 329
350 320 286 404 441 365

This was eye opening. I had been checking velocities at .400" lift. I can see where some of the upper lift turbulance is coming from now. It is a good example of how lift affects velocity.

[106-1194218389]

Here is the roughed in port. You can see how much taller it is. I just noticed that I can see things in the photo that I have trouble seeing in real life. Might be a help to take pictures as you go along. I can see the roof needs to go higher about 3/4" in to SSR.

[106-1194218389]

This next photo shows the chambers. Chamber on left is untouched and on right is one I started working on. If you notice above the seat, not down in the bowl, where the machining ends there is a little ridge, edge whatever. That is what I smoothed out on the other chamber and the .550" lift I had gained the first go around working on the SSR went away. In the back of my mind I think I read someplace not to take that little ridge out. Once again not the ridge down in the bowl but the one above the seat in the chamber.

[bruce]

For future reference try and resize pictures to 800x600 max size, it helps those who have smaller screens so the pictures don't scroll off the edge.

They are nice pictures though!

[106-1194218389]

Bruce,

I don't know what is going on here. When I first put them on they are smaller. I reset them so the are less than 512kb and these last two I set the size to 7" and when I first loaded them they were ok and then when I saw you had added a reply I came back in and holy crap they are big now. I will try to figure this out for the next pictures. This did not do it the last time I posted pictures and I did it the same way. I'll figure it out though. You were right they sure got big the second time I looked at them.

[maxracesoftware]

jfholm .... you should be able to get all the Flow CFM
you will ever need out of a FelPro #1206 intake gasket
port match size .

i'm getting a little over 700+ Peak HP out out the #1206 size
on Dart Pro 1 alum SBC Heads

and as high as 756 Peak HP with a #1207 size
but also pushrods area have been Welded + widened
and maxed-out along with offset Jesels

***************


Also outstanding very nice even shaped Intake Ports !!

Thanks for taking all your Time/Effort in
Flow Testing + Pitot Probing,
and then Posting all your Steps + Data !!
...much appreciated.

Now you can see why its so important just to design
for the Camshaft Lift and Application !

[maxracesoftware]

jfholm ....

My Wife wanted to help out and try Her hand at
Porting with me in my Shop,
so i gave Her a Grinder and i'd Layout out all the Ports
and Scribe them out for Her,
and i'd tell Her => " Be the Line ... just Be the Line " !!

She was instantly very good with a Grinder,
She would follow that scribed line perfectly !

But She only lasted about a Week ....
even though She was wearing Safety Glasses ,
somehow a tiny piece of Metal stuck in Her Eye,
had to go to Eye Doctor and he used a metal clamping
device to hold Her Eye open while he removed the piece !

well that ended Her Porting Career !!!
...and my sort of "Free-Labor"


Here's a Pic of my Wife (Long Hair)
with my youngest Daughter,
as my Daughters getting madeup for a Hi-School Play

[maxracesoftware]

larrycavan ....

here's a Pic of a cast-iron Chrysler SS Hemi Head

its Band-Sawed somewhat up and Sectioned.

See how Laid-Back the Short Turn Curve is ?
thats basically OEM Factory ShortTurn Shape .

That Head has a 2.250 OD Intake Valve

The Short Turn Peak Height (STPH) above the Deck surface
is between .780" to .810"

So .800" divided by 2.250 Valve OD = .35556 PerCent %
Short Turn Height -to- Valve OD Ratio

So checkout Your's ? ? ?
Let me know what you find ?

i know that in NHRA SS Form and because of a Legal Port
Volume CC.... that when i put Epoxy on the Floor
trying to build a higher Short Turn Peak,.. it picked up
Flow on the FlowBench ... but on the Dyno it hurt HP !!

its a pretty small Port CSA-wise that moves a lot of Air,
and at a .3556 Ratio and hi speeds,
it didn't like a build up on the Floor

Again because of getting a Port to check NHRA Legal CC's,
i had added epoxy buidup on the Floor and raised and widened
the Port ..but still limited to what i could do,
it didn't like that at all , even though it flowed more Air.

So "NEVER" put Epoxy on any Short Turn's Apex !!
on any Head i've seen....UNLESS => theres tons of metal
in that Head that you raise the entire Roof the same amount
as you raise the Floor .....but even that can get you into
trouble if the Apex speed gets too high ,
and you loose Swirl, and you can loose some "control" of
Mixture direction into the Chamber where you want it to go.

[maxracesoftware]

[larrycavan]

Thanks Larry...

Not sure what to make of the STPH ratio though. Any decking performed alters that and I'm not so sure the flow is affected from deck reduction.

I will definitely measure it up though and post it. Might well be something very useful to keep in mind.

I've yet to take the throats to the full 90% as well.

Some of the castings make it difficult to duplicate shapes because of the seat / long side bowl & seat / floor matching flaws.

I can cut these ports 3 different ways and get nearly identical peak CFM but very different velocity profiles. It's your tips that got me focused on the velocity profiles more than ever!

After a few years working with your advice, formulas and encouragement, all I can say is porting without a J bend pitot is a complete waste of time IMO....

Anyway...thanks a gain for having a peek at the port and I'll get back to you with some more information.

EDITED -

Update- floor height to valve ratio = .533

Larry C



Edited By larrycavan on 1207194184

[106-1194218389]

Over the years there has been a lot of discussion on what the finish should be on the port walls when you are done. How does the finish affect airflow and velocity? Can I just leave it the carbide finish? Do I use a stone? Should I use a cartridge roll to smooth it? In the past on a few sets I have left it carbide cutter finish and they seemed to run ok. Maybe Larry Meaux with all of your "real" world experience you can elaborate on this.

Thanks,
John

[maxracesoftware]