[slowbird]

Originally Posted by BruceWilkie

I hope there are new opportunities there myself. For a long time I've been of the opinion that our "traditional" layout poses some limitations. If we can get better balance percentages than what we usually see it should help us. If we get same percentages I dont think it hurts us. Worse percentages would not be good and I dont think that will occur.

Wilke what kind of ratio do you think is, 75%?

[pastry_chef]

Originally Posted by cgeise

Bottom line is - If you can get the same cfm with a smaller oval port head as a square port head like a tiger -- you you have a faster head - more efficient

not that simple!

http://speedtalk.com/forum/viewtopic...=26832#p309363

a comment from Curtis Boggs on assumption that Oval is a better port>

"I'd have to say right off the bat that the above statement is not correct.

Simple, the proper port shape is the one that gets the job done properly, .. period!
Oval ports don't just "flow better", .. port shape is primarily about reduction of turbulence in the port, ..
proper velocity profiles, and delivery to the back of the valve.
The shape that does that best in whatever head design you have to work within, is the "proper" port shape.
Studying fluid dynamics and flow through pipes etc can lead you in directions that my influence your thoughts here.
When you have to try an turn air ( or fluid ) or get it around bends and turns, .. or effect how or where the bulk of the flow is biased, .. it's done with variations in shape.
Simply saying one "shape" is the the "one" or the key to the kingdom is just limiting yourself
from any forward advancement past that point. There is no one magic shape.
I have square port shapes in heads and classes where you wouldn't expect with record setting performance."

[cgeise]

Originally Posted by pastry_chef

not that simple!

http://speedtalk.com/forum/viewtopic...=26832#p309363

a comment from Curtis Boggs on assumption that Oval is a better port>

"I'd have to say right off the bat that the above statement is not correct.

Simple, the proper port shape is the one that gets the job done properly, .. period!
Oval ports don't just "flow better", .. port shape is primarily about reduction of turbulence in the port, ..
proper velocity profiles, and delivery to the back of the valve.
The shape that does that best in whatever head design you have to work within, is the "proper" port shape.
Studying fluid dynamics and flow through pipes etc can lead you in directions that my influence your thoughts here.
When you have to try an turn air ( or fluid ) or get it around bends and turns, .. or effect how or where the bulk of the flow is biased, .. it's done with variations in shape.
Simply saying one "shape" is the the "one" or the key to the kingdom is just limiting yourself
from any forward advancement past that point. There is no one magic shape.
I have square port shapes in heads and classes where you wouldn't expect with record setting performance."

I guess Darin Morgan would dissagree with you - as there is a very difinitive explination of this in his manual for his head porting class -- Oval does not have the soft - or dead areas in the corners that square ports do -- offering a more consistant port speed in all areas of the port. If a square port with a cross section of say 4.5 sq in flow 450 cfm - and you have an oval port of 4.25 sq in flowing the same 450 cfm with proper air speed -- the smaller oval will be a more efficiant port, with that being said - old pro stock heads - -square - -new prostock oval - as are the majority of new high end heads. - Not all -- but most.

[Tom Vaught]

Originally Posted by Dragncar

If it will not be able to beat 1100 HP NA with a single 4, whats the point.

I saw a 1200 hp (single 4 bbl) NA "Small Block" GM engine (at a shop this weekend) on a stand. Not a 535 cid engine.

We still have a ways to go, imo.

Tom Vaught

[slowbird]

Originally Posted by Tom Vaught

I saw a 1200 hp (single 4 bbl) NA "Small Block" GM engine (at a shop this weekend) on a stand. Not a 535 cid engine.

We still have a ways to go, imo.

Tom Vaught

CID???

[pastry_chef]

Originally Posted by BruceWilkie

I hope there are new opportunities there myself. For a long time I've been of the opinion that our "traditional" layout poses some limitations. If we can get better balance percentages than what we usually see it should help us. If we get same percentages I dont think it hurts us. Worse percentages would not be good and I dont think that will occur.

I will disagree

better/maintaining I/E flow ratio "percentages" should not be "looked at", even if you are less than 70 percent

[pastry_chef]

Originally Posted by cgeise

I guess Darin Morgan would dissagree with you - as there is a very difinitive explination of this in his manual for his head porting class

actually he won't when speaking in the context of the info Curtis stated, keep in mind who is reading the material..

Vizard does the same

when you obtain extremely high knowledge in a field you can typically always go back to "earlier learning material" and re-qualify statements.. adding buts, ifs, exceptions etc with your higher context and understanding.

the concept reminds me of when Motordaddy was arguing for pages on speedtalk with Mike Jones about the definition of cam lobe centerline - MD even posted a link to comp cams site with the "basic" info for noobs. Jones being one of the best cam designers on the planet.
The difference between a baby learning to walk and a world class sprinter.

[BruceWilkie]

Originally Posted by pastry_chef

I will disagree

better/maintaining I/E flow ratio "percentages" should not be "looked at", even if you are less than 70 percent

There can be a point where a deficient exhaust chokes the potential of the intake flow capabilities. You can only crutch around exhaust deficiencies with ex valve movement(open/close factors) header and intake tuning to a point.

Yes actual flow capacity matters and balance is an important part . Sure, I could improve percentage on a D port, or any other head, and not gain if I dont take advantage of it elsewhere.

??? You seem to be implying that better balance cant be used to improve VE.

If you are improving the intake capability by "x" percentage flow gain should you not be trying to improve your exhaust capability by the same percentage gain??? Could a little more be useful??? Aiding blowdown isnt desirable??? Cutting exhaust pumping losses arent beneficial???

Please explain if you were not playing word games.

FWIW I dont "feel" there is an "ideal" balance percentage. Simply I'd rather have more exhaust capacity than I need or at least as much as I could get.

[cfmcnc]

Some of our Fastest Running Down The track Exhaust ports flow considerable less than some of our Flow bench bragging rights exhaust ports,We like to see real high air speed at the crack of the exhaust valve opening and enough area to not be restrictive.Some of the most refined NA cylinder heads are 55-60% ratio,ieNHRA Pro-Stock.If the 11 pro-port intake can get to 450-470cfm ,with correct air speed and crossectionals and good CFM to MCSA ,we would not be to concerned if the exhaust did not go 70-75%.Bill C.

[Tom Vaught]

Originally Posted by slowbird

CID???

SB design less than 455 cid. Had a very nice looking cast Tunnel Ram on it too.

Tom Vaught

[cgeise]

wow -- looks like the guys developing an oval port should just give up -- and the heck with getting the exhaust working to -----------

[Tom Vaught]

I saw the Engine at "a guy named Tony's" shop

Tom Vaught

[slowbird]

Originally Posted by cgeise

wow -- looks like the guys developing an oval port should just give up -- and the heck with getting the exhaust working to -----------

LOL
That might be a little extreme.

[slowbird]

Originally Posted by Tom Vaught

I saw the Engine at "a guy named Tony's" shop

Tom Vaught

Bet he didn't do that with a wedge head.

[Daniel Barton]

Originally Posted by cgeise

wow -- looks like the guys developing an oval port should just give up -- and the heck with getting the exhaust working to -----------

No, there is just WAY more to it then what some blanket statement covers, notice in the quote he says "with proper air speed" just randomly using an oval shape at the opening does not somehow make the head better, it is very specific to what you are trying to do with the head, like everything else that gets done to a head, it is application specific.

[slowbird]

So when is someone going to post some flow results?

[john marcella]

I here a lot of people talking only about CFM. There is so much more to a head than the flow #s. Correct cross section and design. Then CFM.

And by the way I/Ex flow ratios are crap. Ex area vs HP and rpm and desirable Valve timing. Most of the good stuff on the exhaust side will happen when cyl pressures are so high the the air speed will be at the local speed of sound witch will react to area ,not flow #s. And as long as you can decrease the air speed to less than the local speed of sound by the time the piston is at BDC, there should not be much pumping losses. JMO

[cfmcnc]

John knows,Bill C.

[Tom Vaught]

Originally Posted by slowbird

Bet he didn't do that with a wedge head.

(;>)

Tom Vaught

[65nss4spdGTO]

Originally Posted by Jim Robertson

Calvin,
What did you hit on your head? Spring pocket?? Area between spring pocket and rocker boss? Water?

Sorry guys, been busy and away from the board. We broke through at the top, under the spring pockets. It was an area both Don and I felt would be a problem. There is no reason they machined the inside of the valve cover that way. They give us a pinch point port, then machine the spring pads deep or didn't cast enough material.

As far as the discussion on port shape. If square ports or tall thin ports were most efficient, the Pro-Stock guys would cast the heads that way. That's why the lifter bore and block positions have been designed the way they are. With the success of the Edelbrock performer head, the best improvement made is moving the push rod out of the way and using offset stuff. If the lifter bores position didn't create this problem, we wouldn't need the offset stuff. It's all about usable real estate in relation to the bore size and bore spacing.

Calvin Hill
Hill Performance / Mondello Tech Center
708-250-7420