19 replies to this topic

[Millstone10]

Hi All

After a pleasurable afternoon fettling in the garage I've taken the carbs off for a clean. Looking at the inlet manifold it seems a shame to put it back without some sort of interference.
I think I have read that these GT6 short tract manifolds are hard to improve much but was wondering if anyone has any advice of where and how much to "port"



Apart from port matching to the HS6 carbs (which was not particularly good) the very sharp turn around to the cylinder No2 looks challenging.
Any advice (or pictures ) would be most welcome.

Nigel

[spitNL]

I think the difficult bit will be to improve the breathing and at the same time keeping the flow across the different cylinders as close as possible.
Maybe build a cheap flow bench, or water test, like Bill Blydenstein used to do in his early years.

The water test involves emptying a large container, bathtub?, through the manifold, registering the time it takes.

[Nick Jones]

I'd be inclined to smooth (but not polish) the areas you can reach but leave the basic shape untouched. The odd turns for 2 & 5 are reputed there to try and keep the inlet runners similar lengths and maintain even mixture distribution. Chris Witor actually adds material in on the Mk1 manifolds - not sure about Mk2.

Nick

[Sam]

spitNL, on 15 January 2012 - 01:58 PM, said:

I think the difficult bit will be to improve the breathing and at the same time keeping the flow across the different cylinders as close as possible.
Maybe build a cheap flow bench, or water test, like Bill Blydenstein used to do in his early years.

The water test involves emptying a large container, bathtub?, through the manifold, registering the time it takes.

Wow what a cool idea..does this work for cylinder heads?

[spitNL]

Yes, in the early day he himself built it for cylinder heads.
I read about it in an article in, I think, Practical classics, circa '95.
Shame I can't find anything online about it.

I'm not so sure though how helpful it would be with porting.
To check for even flow across the cylinders, OK.

Edited by spitNL, 27 January 2012 - 06:26 PM.

[Urge]

Dont use water to test for air flow, all it will do is to show you bigger is better, and thats so not the case

[davesideways]

Good point innit, water can flow and form to any shape but it cannot be compressed or controlled by applying pressure unless there is an outlet, it's good to be like water

Air can be at any pressure, compression, negative or positive and can form depressions etc.

Water will tell you a 1.5 carb flows more than a 1" one, thats about all

[GHR630]

Of Course! You can't f*ck with physics.......

I've no idea if the saintly Bill actually supported this..... but I bet there are plenty of those "experts" out there who would support the theory. Just go to any of our shows an listen to them bang on.

[JohnD]

I agree. That's the problem with aerodynamic testing. Water just doesn't give you a suitable model for air flow and neither do small scale models in air. And that's why any F1 team with the money will invest in a full scale wind tunnel.
If you can blow, or suck, air through the manifold, it might be worth injetcing some oily dye into the flow. The apperance of dye deposits on the walls might show you about laminar and turbulent flow, in the same way that road dirt on the outside of a car can show you. But then, was the turbulence built in on purpose?
John

[Millstone10]

It would be really interesting if someone had some results of putting the manifold on a flow bench? I havn't read this anywhere ?

P.S. Water ain't air - Have a look at this one if you get a chance - Hydrodynamics of sailing
Cant say I've read it all as I was borrowing it while in a donger... but the jist was enough for me.

[ncoll]

JohnD, on 29 January 2012 - 11:07 AM, said:

it might be worth injetcing some oily dye into the flow. The apperance of dye deposits on the walls might show you about laminar and turbulent flow,

If you are drawing air through the manifold,using a vacuum cleaner or other electrical equipment, do not inject any liquid whatsoever into the airflow, especially anything flammable. If you do, the last thing you are going to hear is the beginning of a big bang. If your car is normally aspirated you will need to draw the air through the manifold, (not blow it through) make yourself a manometer with a small metal tube on the end, with this you can probe the airflow in the manifold and plot where the airflow is within the manifold.
neil

[GHR630]

"Quote: water ain't air", correct. You can't f*ck with nature either. Aerodynamics: A penguin is a bird and can't fly - but it swims like an angel......'nuff said!

[GHR630]

Oh, and BTW, nice to hear from the man himself. Good to hear from you Neil...............................................

[GT6Steve]

I agree, hope all is well in Neil-World these days....

[Millstone10]

GHR630, on 29 January 2012 - 06:04 PM, said:

" You can't f*ck with nature either"

Although according to National Geographic nature is all about f*uking, no?

[GHR630]

Millstone10, on 29 January 2012 - 11:31 PM, said:

Although according to National Geographic nature is all about f*uking, no?

I wish..............................!!!!!!!!!!!!

[spitNL]

Well I didn't want to put it down that strongly, but I agree about the drawbacks.
Which is why I only suggested it for checking even flow.

I did find the Blydenstein article, turns out it was in the throroughbred and classic cars of April '91.
http://www.borgward....blydenstein.pdf

[davesideways]

Strength of opinion was never one the weak points here.

[ncoll]

GHR630, on 29 January 2012 - 06:06 PM, said:

Oh, and BTW, nice to hear from the man himself. Good to hear from you Neil...............................................

GT6Steve, on 29 January 2012 - 06:22 PM, said:

I agree, hope all is well in Neil-World these days....

Hi George and steve
everything seems to be ok in neils world, one step forward and two back. Hope the weather is a bit warmer where you are steve its gonna be 1 degree above freezing here on wednesday all day.



neil

[Nick Jones]

davesideways, on 30 January 2012 - 04:46 PM, said:

Strength of opinion was never one the weak points here.

Good thing too

Nick