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ported b234f flow chart and graph

I would reduce the MCSA a bit ;) YES a big hole looks great on a flow bench at 28" of water... in a IRL engine pulling somewhere around 300" of water things becomes a tad different... Pentroofs of that style has bad pressure recovery in the chamber... if you want good flow in the running engine instead of in the flow-bench, I'd start the pressure recovery BEFORE the valve ;)
 
The numbers look great, not because they're big, but because what they'll support the engine's desired power curve. I'm not making sewers, I'm basing my average airflow upon accepted formulas and rules of thumb around performance machinist's circles, which is then verified by the flow bench, and therefor the numbers are cross checking and regulating each other to as minimal the space can get, before it's too much.
 
SR71TurboCoupe said:
The numbers look great, not because they're big, but because what they'll support the engine's desired power curve. I'm not making sewers, I'm basing my average airflow upon accepted formulas and rules of thumb around performance machinist's circles, which is then verified by the flow bench, and therefor the numbers are cross checking and regulating each other to as minimal the space can get, before it's too much.
Click to expand...
Thats not what I ment... for instance... the stock port opening (gasket flange) flows like 270cfm as it is, enlarge it so it equals (in therms of area) a 45mm round hole then that part flows about 380cfm... hence no point in digging a huge hole at the flange ;) The "plug" which restricts flow in just about 99% of heads are the valves and the area just above it and below it ;) as for theese heads, making the flow go down AT the valve will result in less flow than by cross-flowing it slightly, aiming it AT the valve effectively puts the valve in the way. Use 6mm stems and 40-41mm valves (yes there is room) and fill in the "roof" in the correct matter and lift the floor a tad with a oval mcsa with an area similar to a circle of 32mm for each valve and make the area just before the valve seat angle as big as you can make it without compromizing the seat. You'd be surprised :) PS almost no point in hunting flow on the floor side of the valve having a sharp turn there in the seats flows more due to the larger area and better pressure recovery. The seat and top-cut angles you may choose at your peril, the angles before the valve is of no real issue as long as it got enough metal to hand form it to the rest of the "diffuser" in the port. :) The best ting is a venturi style port flows an equivlent 10% more in a running engine than a typical port does in flowbench numbers...
 
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Fill in the roof?....weld it? Epoxy?
Oval Min cross sec. area is where, exactly? I have my own ideas. I'm interested in yours.
What is your idea of an ideal bowl to seat transition?
If you have pictures, that would be great!
 
poulson01 said:
Fill in the roof?....weld it? Epoxy?
Oval Min cross sec. area is where, exactly? I have my own ideas. I'm interested in yours.
What is your idea of an ideal bowl to seat transition?
If you have pictures, that would be great!
Click to expand...

Surprised? Not the first one then :p I use epoxy, Scotchweld 2216 aerospace stuff, good against both alcohols and hydrocarbons. Its sandable and machineable, but still kind of rubberish so it expands and contracts with the material in the head.

I usually never base my ports on a minimum diameter in the seat... the seat insert is just a harder metal part to be wear resistant. The seat has to be round and cut by a Mira or similar, the rest before and after can be at your peril, the cutter don't HAVE to decide the shape and lesser diameter of the seat insert, if so was the case F1 and such teams would REALLY struggle.

I decide upon a mcsa area to provide the flow needed for the application, whatever maximum power is desired I maximize the valve size non the less. Two mcsa's of equivalent ?24mm flows to provide 239 cfm at 28"h20, for the 262 head two mcsa's of ?32mm would be good for in the range of just over 400cfm. Usually at a velocity that is supposed to be "impossible". So why dig a massive hole?

Regarding the position of the mcsa i decide upon a 7? (ish) taper from the chosen mcsa size to the inner radius of the seat angle cut (as if it was inline with the stem) then make it oval, straight down on the side walls and tapering (along a curve for instance) in the roof and floor. Works just about everytime :) If you get for instance 380cfm from this type of venturi/pressure recovery type port, it'll flow in the running engine like a 418ish cfm regular port (factor of 1.1:1 aprox), but with the advantage of the higher velocity (more bottom and middle grunt).

In aiding to design such things i use CAD software, can be done manually, but more hassle.

The example is from a whiteblock head for my new daily driver, as I'm still doing R & D on a 262 head I got hold of a week ago...

The bare model like this (I use rapid prototyping, but no worries the orange outlline is stock port, so it mostly fits inside it...) only flowed 215cfm as the shape is on the model, some incredible minor adjustments and it got 239cfm (not too impressive? concider the factor of 1.1:1 i mentioned earlier ;) ) @ 12mm lift on 2x 34mm valves, point beeing mcsa limited. I won't tell the details, as I don't want to post a blue print to be copied... The port will support more with slightly larger mcsa and some more lift, beneficial in forced induction applications where the velocities will be high anyway...





Revealed too much "best of holding it for yourself" stuff already I guess :p
 
Thanks for sharing Flyfaen.
I hope to see another post with your opinions on the 262, after you've had a chance to study it a while.
 
Prolly same as mine. In some scrap pile.
This kinda stuff is fun, until the economy bounces back and you have to get up and go to work again.
 
gashog said:
Prolly same as mine. In some scrap pile.
This kinda stuff is fun, until the economy bounces back and you have to get up and go to work again.
Click to expand...

Nah, not yet :-P

I bought myself a house last spring and have been busy since then, setting up my garrage, and my flow-bench is not installed yet (aka I have to make it, got hold of good condition twin-screw so aiming for pulling more than 100"+, probably have to make it diesel-driven as my 63 Amp main fuse and the closest transformer won't be up to the job... the screw will draw aprox 30hp at peak flow at 100"+.....)

Tho no need to keep my white block final port any secret anymore...

Flows those 239cfm from 10.8mm (.425") up, flow at my lowes measured lift of 1mm (.040") is 42cfm.



Also found a cut of 262 head, and there will be needed some welding to make the ports work in the 380cfm region WITH 390fps+ velocity at 28"

Problem can be seen here, with larger valve seat inserts there is no room to lay down the floor enough, as for the roof, there will be needed some amount of epoxy to make that bowl-like dip go away, its a huge chamber roll-turbulence killer, actually to the point of making me unwell to thinc that it was actually COSWORTH that designed this head back in the day (just basicly a upscaled ford YB head). The ID of the new size seat angle cut will be aprox where the OD of the stock seat insert is... basicly the port just blends up to the seat angle cut, with quite a negative seat insert angle upstream of the seat angle cut, on the SSR (or no radius :-P side) :)

Red ring show area of concern... prolly need to mill down there and weld it back up, a genius thing tho is that the port then will be so straight that the head is really easy to CNC-port for flow equality :)

 
I need to buy the plate, should be this week.
The head gets bolted down to some 1/2 steel plate to prevent the warpage. also a bunsen burner underneath keeps it nice and evenly heated.
SOrry guyz. New job, house hunting, etc.
 
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