I would like to know why cylinder heads are described as "ported and flowed",
but when asked for the particulars regarding the actual flow test, I am told no testing was done.

What is up with this?
Does "flowed" not imply actual testing?
How can a head be flowed without a flowbench test?

Cheers

PK

 

sounds like someone has done the work themselves in the garden shed........

 

With a dremel probably.
Years ago like 20 odd I used to port two stroke bikes with my files .It was always a case of take as much out as possible,AND they were always faster .These days my mate has a flow bench .You can totally ruin a head if you dont have a clue what you are doing.It does not allways pay to take as much out as you think.

 

Here is my response to a fellow with a head for sale:

Why would you say the head was "ported and flowed" if the head wasn't flowed?

His reply:

Because the head has been ported and flowed. Its not been flow tested.

WTF?

How do you flow a head without a flow test?
That is like measuring something without a ruler.

 

hello, but what is the point of a flow test if it doesnt reflect the piston movement ? and the effects this has on the actual flow.?

 

Because most heads (infact tuning) in the ford world are sold on bullshit and black magic.

A lot of people port heads but not many make the investment in money / equipment and time to develop one properly.

 

my dads mates used to do this on mopeds and drill out the injectors

 

ow and i think it will be sold as that because every other head sold is ported and flowed

 

I have seen first hand and heard many times over of heads that show good "flow" results but don't make any better power. In fact I know someone who was in charge of a VERY prominent 80's Touring Car engine department and he says honestly that 9 times out of 10 if something "looked" good it performed good.

I have done a good few of my own heads now and one in particular was on my YFZ450 quad, my brother in law paid to have his done by a "Pro" and there was NOTHING in it at all between both quads. And both showed good gains. My issue with paying the guy was that he had only ever done a few Yamaha 5v heads and was a Honda man, well that to me means he would be using your time and money as an experiment.

I think if you understand the basics of an engine and how it operates it is possible to do it yourself to a degree. I don't just take big lumps of alloy out wherever I can, but I also agree that if someone has done 100's of 1000's of the SAME heads they will no doubt have a few tricks up their sleeve.

 

very true mate cant be too hard to do a little bit can it!?

even if its just smoothing it out or whatever and not actually taking loads of metal off

what tools etc did you use to do yours?

 

is ported and polished the same as ported and flowed then? i bought a head described and ported and polished from a garage but wasnt given any particular technical info. it was nice and smooth in the chambers though.

 

Thats because they do not know how to use their flow bench or how to interperet the data.

I could achieve great flow from a port by simply making it larger. What you should really be looking at to compare heads is coeffecient discharge for a given cross sectional area or perhaps something like cfm per mm square valve area.

 

i think flow means it was flow tested or meant to have been

 

i cant recall seeing a head described as ported and flowed but ive seen many listed as ported and polished.

 

Cool moped if it ran EFI

 

Your quite correct, he only ran the engine department for a Touring Car team, had NO clue on actual engineering and flow dynamics.

I am not saying he doesn't believe in a flow bench, my point was I could show you some figures that say it flows much more than it used to, and that would mean fuck all.

I couldn't give a fuck, no matter what people put up on here there is always some clown telling them they are wrong. Charge on.

 

Surely there are different types of head work needed for different types of engine?.
On my old burton engined mk1 escort which had been ported +polished, the inlets were larger but still had a slight roughnes to them, when i questioned it i was told it was to disturb the flow and aid the mix of air and fuel .
When i had my saff head done , all the ports were smooth. I guess different engine builders and tuners have different ways of doing things ?.

 

Perfectly possible to make a good head without flow testing each individual one, once you know what works its just a case of replicating it, and the best way to find what works is to test it on an engine.

flow test data is useful, but its also not directly relevant on its own, if you compare 2 heads for sale and go for the one with the biggest flow value, it tells you nothing about how it works on an engine just by looking at that figure in isolation.

like garage19 says, flow benches are a useful development tool to get max flow from min size (essentially the desired end result), but ultimately if you want to make a head with a big flow figure to sell it then you just make the hole bigger!

I have no idea what the flowbench value for my cylinder head would be, but I do know that it works very well on my engine.

 

Read your own post Barry Boy. You stated you had heard many times over that heads with good flow figures just did not perform. I am telling you why. No mention of touring car guy. Mind you if he did know his stuff he should have also explained this to you!

You then say your touring car friend says if it looks right then 9 out of ten times it is right. Looks right to who? Someone who has spent hours developing heads on a flow bench or some kid who wants to tune his car?

I'm not saying your touring car friend doesn't know what he is talking about, more that you don't know enough to quote him in context.

 

You might not know or need to know but the important bit is i bet Neil Roper knows. If not for your exact head, then the one he used to develop the port shapes on.

I bet he could quote you CDs, cross sectional areas, port velocities and where they are highest/lowest across the port and where the flow tends to exit the valve into the chamber. All things you need to know to develop a head properly and all things he will have used a flow bench for.

 

Chip tell me how do you develop a seat angle with out a flow bench and design the lift you want on your camshaft.

 

Doug, agreed, its important info in developing a head, its not important info when buying one though.

If there are 3 heads advertised each with a CFM value, this alone tells you nothing useful about the head IMHO, invariabley the biggest port job will be the one with the biggest number, but that doesnt mean its going to give the best area under the curve on my engine.

 

You dont, you totally missed my point.

 

I don't think Chip is arguing that you don't need a flow bench to develop a head, merely that if unless people have a basic understanding of fluid dynamics the numbers that get quoted can be mis leading.

 

Exactly!

If some heads are for sale, and have quoted flow values, people will just buy the biggest number they see, and the odds of that being the best head for their application are slim!

 

I think the important word is development. If the head worked before and the head man is good at his job there would be no need to indiviually flow test when they can do it by eye.

 

Thany you guys for your answers to the question raised.

I agree that actual head flow numbers don't necessarily mean higher output.
A large cross sectional area will show better flow numbers, and not make
the power output it could.

However, having some guy say they "look good" is a bit of a stretch - even for a
very experienced head porter. I can change the valve seat angles, and change the
head flow by 5 cfm ( you can't and wouldn't know unless it was flow bench tested )
I can also remove 1mm of material (on the wrong side of a CVH port) and reduce the flow by more than 5 cfm - again you cannot look at the port and see these differences.
The backside shape of the valve also has a large impact on the flow - this must be matched with a specific short side radius and valve seat angles - or the resulting flow will be lower than expected.
This work cannot be done without a tool to measure the changes.

A good scientific head porter knows (or should) the importance of port CSA, port velocity,
etc..

A flow test also does not guarantee that the head porter knows what he is doing. It is just a tool to measure changes being made to port shape, valve seat angles, and port cross sectional areas.

One has to have a measuring device of some type - the engine has a dyno to measure power output, the car has a racetrack lap time to measure performance.

 

Canada1 your spot on. its a bit late when on the dyno to find out your porting has done nothing to increase horsepower.
thanks
andy@amt

 

It's just different words to describe the same thing. I tell people my head is "gas flowed" or "ported and polished" depending on which comes into my head first because MOST people consider these terms interchangeable. This thread mentions "ported and flowed", well that's a slightly different mix of these words. Perhaps technically there's a different but in the real world these are interchangeable terms.

 

The term "flowed" can mean either

"Tested for flow"

or

"Modified to improve flow"

And with experience there are plenty of modifications that you can do which you know will improve flow without you needing to test them, then there are fine details you do need to test, so sometimes the term might apply in one context and sometimes in the other.


Cant see its worth getting worked up about though.

As for a head "looking like a good job" etc, i would be more interested in what it feels like generally TBH as your fingers can feel things your eyes dont see.

 

Just found this, from some bloke called Keith




Still, what would he know?

 

Hi Chip,

Interesting passage.
Because one fellow has the "touch" doesn't mean that us mere mortals don't require
measurement tools.

 

The fellow in question was Keith Duckworth

And compared to him, I doubt anyone on here would lay much claim to having a magic touch with engines, lol

 

Chip, since you love minis i'm sure you will have huge respect for Dave Vizard. It would seem he is the complete opposite to Keith Duckworth as he is a prolific user of flow benches and has written many articles on them.

 

Not really mate, I just view him as a collator of information really, got loads of respect for him as a technical author, but would sooner go to someone like a guy I know quite well called Rob Walker (he actualy helped me build my track mini engine over a decade ago now) who Vizard used to be a junior to at oselli IIRC

And he is more a "stick your fingers in and use your experience" kind of guy rather than letting a computer tell him if he has it right or not.