Port velocities

[106-1194218389]

Larry,
My actual cfm before porting was 222.3 cfm at .500 lift. My engine piston CFM was the 245 cfm so that is what I was thinking of shooting for because I am not building an all out race engine. The port volume is now up to 186 cc and expect 190 - 193 cc when done. Right now my CSA is 2.06 so I have gained some. I am going to flow again tonight and check velocities. My cam is .510 lift and I have check the velocity at .400" lift. My thinking was on the same line as yours. Also that is probably pretty close to where the piston speed is the greatest. I hope my thinking is ok on this. Thanks so much for your input on the epoxy. I was trying to aim for the .040" thick but I either mis-measured or the machining is off on the heads. I only measured one port so my mistake. No hole yet but the little blister like part when it gets real thin. I will fill all the rest first before grinding. Will that epoxy work like you described on the outside of the port where the oil is?

Thanks,
John

[maxracesoftware]

Will that epoxy work like you described on the outside of the port where the oil is?
*********************

it will work OK,
to use on the outside you must sort of "Scotch-Guard"
protect it with another clear expoxy coat like
Devcon 2-Ton Clear.
You must keep hot oil from getting into the feathered-edges
and behind the epoxy lifting away over time,
by using another coating ontop of SplashZone.

there was another Epoxy Company that had a superior
easy flowing epoxy that would work perfect as a coating
but they went out of business. its funny how with such a
great epoxy product that happened, i guess poor marketing ?


Be very careful and very patient,
with a bunch of constant thickness checking
when porting + maxing out the Pushrod Walls !!

otherwise, the very thing you hoped to accomplish
by widening that area,..will now be thwarted if you need
to go back in and build-up that very area with Epoxy
to cover up a Hole or Blister spot !

the Pushrod CSA will always be limited or smaller with epoxy

[106-1194218389]

I know what you mean about a good product going away. It breaks my heart when that happens. I was mulling this over in my mind. I do not know if it will work, but what about rolling some .030" copper sheet to fit the outside of the port where the pushrod is and solder it in place? Have you ever tried to solder anything to the cast iron? I never have. I know in some heads we will press a brownze sleeve in the head bolt hole between the intake port bowls when making the bowls larger, although I have not ahd to do that for awhile. I wnet to both Goodson's and Reher - Morrison web sites and could not see that epoxy listed. I guess I will have to call.

Thanks Larry,

John

[Dave W]

[106-1194218389]

Good idea Dave. I have had pretty good success with JB Weld and to do it like that I would not need alot of JB. I have some copper tubing and may fit right in there. Dart really machines it large there. One thing the Dart cast iron seems pretty darn good stuff. Seems to be high nickel and is very shiny where I ported.
John

[maxracesoftware]

[106-1194218389]

Thanks Larry, That makes me feel better about the solder angle. In the mid late '70's my cousin and I were running a 1931 high boy Model A roadster in B/SR. When the first Turbo Heads came out we were some of the first in Salt Lake City to have a pair. We completely removed the pushrod side of the port and Epoxied some regular old window screen on the area and then slowly built up with layers of Devcon. Never had a problem and the car ran 10.0's at 135 mph here at 4300 ft altitude. We always ran with our fingers crossed but never did have a problem. ALso built a set of raised port 383 Plymouth 906 heads building up on top of the ports with Devcon. That was the first year NHRA let you port in Super Stock. They let us run them that year but the next year they frowned pretty hard on our "ingenuity" :;):

John

[Dave W]

Forgot to mention but larry allways is one step ahead. The rockers are offset. You will have check that without a doubt. I went about 1.100" wide at the push rod if I can remember . The heads are older 180's and were horrible. My heads flowed 192 - 198 out of the box and finished at 254 with a 2.05 IN.

Dave

[106-1194218389]

Boy am I pleasantly surprised! Just flowed my Dart 180 cc heads. The CSA at the pushrod is now 2.131 sq inches (1.920"h X 1.110"w). It was 1.791 sq inches stock (1.800"h X .995"w). I was expecting the velocities to change, but not nearly the flow I gained. Below is the new velocities at first the pushrod area and then the SSR. Left side is the pushrod wall and right side is the divider wall. They are FPS at 28". Top of port to bottom. As you can see the fastest speed is right on top of the SSR now. It has come down but still too fast. Check my previous posting for comparison.
pushrod SSR
338 320 286 286 286 286
338 303 286 286 286 286
320 268 248 365 365 365

flow at 28"
stock port ported at pushrod only

.050" 28.5 30
.100" 59.3 60
.150" 90.1 91.6
.200" 118.8 121.3
.250" 146.5 150.1
.300" 169.7 175.4
.350" 192.1 199.7
.400" 208.0 220.8
.450" 217.7 238.8
.500" 218.5 251.3
.550" 217.4 224.0
.600" 215.9 227.7
.650" 215.5 230.9
.700" 214.4 231.0
.750" 214.3 229.7

From what I can gather listening to Larry M. and the Porting by the numbers by Darin Morgan and Flow Theory by Harold Bettes I feel like I need to address the SSR. The flow velocity there is still too high causing the big drop at the convergence which happens to be at .550" lift on this head with the 2.05" valves. My nest plan of attack is to lower the SSR a little and widen it some. I will then play with the bowl area. I feel 260 cfm is very possible out of these heads with correct velocities.

[maxracesoftware]

[106-1194218389]

Thanks for the reply Larry. Today I will play with that area you talked about and I will leave the SSR height alone. I am like the old carpenter, measure twice and cut once. So I come to the forum and ask twice before I grind. Is this also the area that Darin Morgan spoke of moving the bias of the throat .050" towards the SSR? What are your thoughts on making the SSR area wider at the floor? I sure can see the challenge now of doing a good set of Super Stock heads. After you get the push rod area bigger where in the honk toot would you put the epoxy back in to fill in what you have removed to meet legal CC's? I guess that is the ancient Chinese Secret. Thanks as always you guys and I really appreciate this Larry. I do not have the time or money right now to waste new heads prototyping. Well back to the old grind.

John

[maxracesoftware]

yes i'd go widen the floor's width at the short turn,
but theres water there waiting for you,
you need to be very careful.

the more the port "turns" like a 23deg design -vs- a more
modern straighter shot design,
the more short turn width you need at the Apex.
it can be as wide as the Valve's OD if its possible with enough
metal to safely port.

there's more CFM gains to be had working the Short Turn
Curve "away" from the Valve Stems edge in the Bowl,
that is , using the valve stem's edge as a visual referrence
point and "biasing" the short turn curve away from the
center of the Bowl, the center of the Valve Stem diameter,
or edge...its called "laying back the Short Turn"

what's happening to you is that your Short Turn Curve
is turning too far into the Bowl, this is fasely picking up
Flow Numbers until around .500" Lift , then flow drops
after .500" lift as the valve starts lifting away from .25 L/D,
as it was using the Valve's Head to keep flow attached.

once the valve head moves further away ,
the flow separates and drops.

Look at it this way,
if just Dry AirFlow cannot stay attached,
that is, its entirely "TOO-Sensitive" to your Short Turn Curve,
then how do you expect Mixture of Air and Gasoline,
which is heavier, to stay attached ?

thats why i call it "False-Flow"..it looks good on a FlowBench
but won't make the correct HP for those Numbers,
thats what Darin seeing.

all that type of Flow will give you is slightly better low RPM
TQ and HP as it keeps the FPS up at low RPMs,
but as RPMs increase its choked there and it doesn't make
the mid to hi rpm HP numbers and will use
more Fuel on the Dyno. it will spray wash the chamber wall
directly across, it will be clean there.

You want to take "Sensitivity" out of the Port,
you want the Flow to stay attached no matter what.

if you get the Short Turn Curve laid-back more,
it will flow great everywhere and do so with a backcut
on the valve like 30deg or so,
the first sign the Curve's wrong, is you Port flows more Air
without a BackCut from .4500 or .500 lift to .800+ Lift

when things are correct, it will love a BackCut,
the ports sensitivity will be gone !

getting back to "False-Flow",
its possible you can grind the Short Turn Curve one way,
loose CFM numbers, but it will not fall off,
and make more HP...this is something like Darin's talking about

but when its correct, you gain the entire Flow lift range
and its worth more HP that way !!!

leaving the short turn curve fat will give you more
low rpm to mid range TQ and hurt mid to top end HP,

grinding too much curve away or laying it back too far
gains hi rpm HP, but reduces Peak TQ to low rpm TQ

its a balancing act getting the Curve correct for the
application....thats why its best to have a modern
straight shot port that takes the load off the short turn,
and can use + handle higher FPS

[WPH]

Would it be possible to get a picture of above? Some Photoshop job or handsketch? I'm having a hard time "visualising" this because
I can't understand all the terms used. I get the overall picture but miss some of the "finesse".
I have a type of head that sounds like this one (as per short side apex/curve).

[106-1194218389]

Update on my head - did the bowl at the SSR - Tried to do it the way Larry M suggested. I did not do much, but I may have done more that I should have, but maybe not. I still have some snaggles in the bowl to clean up from their machining. But here is what I got: left side is pushrod side and reading are top to bottom of port.

Velocities first then cfm below

Pushrod SSR (both at .400" lift)

320 303 286 248 248 248
320 303 286 268 268 286
286 268 248 350 365 350

Flow @ 28" before bowl work and on right after SSR bowl work.

.400" 220.8 218.8
.450" 238.8 237.7
.500" 251.3 251.7
.550" 224.0 253.3
.600" 227.7 231.1
.650" 230.9 232.5
.700" 231.0 232.2
.750" 229.7 229.9

.600" up seemed to be very turbulent

btw The first run on this test showed 280 cfm at .550" lift and and thought boy that Larry M is a wizard
then I noticed I had left the spark plug out and my elation went into the toilet. But still a 29 cfm gain at .550" lift is pretty good.

[maxracesoftware]