Poll - Short Turn Curve Bowl Perspective

[gmrocket]

pic #2 here also.

[Amilcar]

Wow .. that's a big surprise to me !

i thought at least 7 out of 10 would Port looking using Pic# 1

so far ..its way opposite .

i thought about asking this , because i had a few recent Emails
and all the ST Curve Pics they sent were like #2 Pic

i had to flip them vertically in software to study what they sent me

Larry,

I think most use pic 2 position, because it´s a more favorable position to grind too.
Now I`m curious..
Do you grind the short turn on pic 1 position too?

[maxracesoftware]

Larry,
I think most use pic 2 position, because it´s a more favorable position to grind too.
Now I`m curious..
Do you grind the short turn on pic 1 position too?

i always Port from the VJ Bottom Cut -to- the Intake Short Turn Curve towards the Floor's Apex area , as in my 1st Pic
The Intake Short Turn would be directly like 12:00 O'Clock or between 10:00 to 2:00
the Long Turn would be directly 6:00 O'Clock or between 8:00 and 4:00

Same thing for Exhaust Short Turn Curve ( with the Head turned around for Exh side )

Now i have to ask this Question :
Which way are you Porting the Long Turn in the Bowl up to the Valve Job Bottom Cut ?

its going to be a big shock to me if everyone's Porting the Long Turn with the Head still facing the same way as my Pic #2
... that is , like jcisworthy 's #3 Pic !

If i had to Port my Short Turns like my Pic#2 ... i just can't comprehend the Shape i wanted

i'm pretty sure i've never Posted a Pic on any Forum with the orientation like my #2 Pic
.... no one ever said anything to me all these years ... so i just thought everyone has been Porting like me ???

[mag2555]

The short turn needs to be atleast 1/4 arc of the circumference the Throat is in the bowl.

The more the short turn height is away from this minimum the more D shaped the width of the short turn needs to be below the bottom cut ,which in turn calls for a wide flat approach on the floor to the short turn.

Excuse the clay used to hold up the template.

[jcisworthy]

I want to amend my order of operations, 1-4

Following this progression works best for me. Leaving the short turn for last sets me up for the best success when shaping because I know what the runner is doing up to the turn, shapes, velocities etc.

In my opinion, not knowing what the air is doing in a finished or close to finished form can lead to a shape on the short that is not the best for that particular runner

Chamber work should be done before the final short turn shape also because that will make a difference on what the air upstream is doing also

The chamber can be done at any point after the valve job and before step 4 or final short turn shaping

[Amilcar]

Larry,
I think most use pic 2 position, because it´s a more favorable position to grind too.
Now I`m curious..
Do you grind the short turn on pic 1 position too?

i always Port from the VJ Bottom Cut -to- the Intake Short Turn Curve towards the Floor's Apex area , as in my 1st Pic
The Intake Short Turn would be directly like 12:00 O'Clock or between 10:00 to 2:00
the Long Turn would be directly 6:00 O'Clock or between 8:00 and 4:00

Same thing for Exhaust Short Turn Curve ( with the Head turned around for Exh side )

Now i have to ask this Question :
Which way are you Porting the Long Turn in the Bowl up to the Valve Job Bottom Cut ?

its going to be a big shock to me if everyone's Porting the Long Turn with the Head still facing the same way as my Pic #2
... that is , like jcisworthy 's #3 Pic !

If i had to Port my Short Turns like my Pic#2 ... i just can't comprehend the Shape i wanted

i'm pretty sure i've never Posted a Pic on any Forum with the orientation like my #2 Pic
.... no one ever said anything to me all these years ... so i just thought everyone has been Porting like me ???

Yes, short turn sequence the same as yours but, with the head flipped 180*, as on pic#2.

Long turn in the bowl, like yours pic 1, perfect sight thru the valve guide.

I don`t think many will port the long turn as on your pic#2.

I have never though about this before.
Maybe just me but, i feel way harder to control the cutter agains the gravity, instead just side to side, back and forth. Mainly on the short turn, where cutting involve lots of back and forth.

[foxchassis]

Which way are you Porting the Long Turn in the Bowl up to the Valve Job Bottom Cut ?

Larry
I port long turn /bowl as in jcisworthy number 1 pic. Guide boss is done in same position and shaped as my very 1st operation, 2nd
comes roof up to and past guide boss with head deck surface up. I should say that when doing the str (last operation) that I pick a
'dull' egg/oval, I get more control without digging in.

[mag2555]

The routine for me.
1) Size the Throat to within 5% of the percentage I am looking for by means of a template.
2) make short turn template and begin to shape that to close to the needed arc
3) use modified Throat template to cut port as needed to get to the new crown of the short turn in the window area.
4) do first flow test with the modified port to see where I am at.
5) replete procedures to get to final Throat size and then grind the rest of the runner out on back to the flange for the needed port circumference and expansion rate .

Please note that the order of my pictures are reverse of what they should be.

[groberts101]

I try real hard to listen and learn new things but you guys are hurting my brain.

Right or wrong, I typically port from the combustion space outwards to the inlets and exits. My theory is that the short turn can only be made so good for most castings and any given valve size and going from the inlet inwards to the SSR and around towards the choke might end up with an improperly shaped meeting/transition point or more pronounced ski jump effect. Also try to consider that the combustion spaces energy recovery can only be what it is for any given valve angle and chamber design so I tend to start there and work my way towards the inlet.

So, unshroud the valve wherever possible, work the valve seat exit radii and match those top cuts as best possible into the chamber for any given casting

Choose the throats choke size based on speculated(pre-measured) cross sectional area capability or required flow volume needed to achieve the desired result(NOT just hogged out for max flow numbers but based on expected velocity needs/requirements).

Then onto excessively streamlining the guide area so that I can better manage and estimate available area over the turn( I tend to almost always split/remove the heads built in guide material and expose both sides of the bronze liner). Also like to shape guides leading and trailing edges if material permits and sometimes add a bit of putty even if it doesn't. Note that if you don't do your own guide work and send them out to someone.. they'll probably tear them all to hell due to the added fragility of splitting the guides in that fashion!

Shape the SSR in roughly expected shape and floor width for the available cross section over the turn

Then go out to the entry and work my way inwards till I can match the apex to the already roughly shaped SSR.

Takes a few rinse and repeats to sneak up on an equalized velocity profile and sometimes the shape you want for the SSR isn't necessarily what you end up with to settle it down. Keep the crutches as small as possible by fixing all the other weakest links first.

Granted my stuff certainly doesn't win any championships like some posting around here but my heads are almost always overachievers and do well enough for what castings they are based off and relating to the budgets involved to get there.

[maxracesoftware]

this is how i'm looking + Porting the Intake Short Turn Curve


this is how i'm looking + Porting the Exhaust Short Turn Curve

[maxracesoftware]

Porting Templates ( Tools of the Trade ) :

[maxracesoftware]

[maxracesoftware]

Vertical Template :

[treyrags]

Good stuff. Thanks for sharing Larry

[foxchassis]

My most recent addition to my porting tools. Would struggle without it. The goose neck light in the background is flat wore out, but it did
have a good magnetic base , which I will adapt to new light.

LED Clip Lamp #0771477 at 'Lowes' lighting department, 268 Lumens $20.00 ?