924Board.org

dreamgts · Joined: 29 Dec 2009 Posts: 504 Location: malta

Hi guys, does anyone have a diagram or schemetic of where to and where not to port/polish a 924 N/A head.

Thanks
dreamgts
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2 PORSCHE 924 (CURRENT PROJECTS)
2 CLASSIC CORTINAS (FINISHED)
1 CLASSIC FIAT(FINISHED)
1 CLASSIC FIAT 132 2000CC(JUST PURCHASED)
4 SUV'S
2 SEDANS
1 OPEL PANEL VAN
WIFES SUZUKI ALTO

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Match the ports to the manifolds, and reduce the amount of material around the valve guide.
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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

Martijnus · Joined: 29 Dec 2006 Posts: 2019 Location: Netherlands

Don't polish the intakes.
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"Rule: Turbo's make torque, and torque makes fun." (C. Bell)

924 "50-jahre", 1981.
MSII/extra, LPG, ITB's, 5lug.
To be turbo'ed in a while.
Killed her at the Nurburgring, Porscheless at the moment

Joes924Racer · Posted: Sat May 21, 2011 11:34 am Post subject:

Some say its ok to get rid of the flat top on each exhaust side port..
and maych it to a header or whatever your runnin .... others say thats a no - nooo beacuse the flat spot creates turbulance and speeds up
the exhaust flow ... me I went ahead & made it round.
_________________
1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

dreamgts · Joined: 29 Dec 2009 Posts: 504 Location: malta

So what is best therefore is to work on a guide gasket based on the intake manifold,, should we just port the outer section and form the port as a cone type or do we have to remove material from the inner port? It seems the water jackets are pretty easy to go thru when porting around /near these. Is it a good idea to ploish the inlet manifold too once we are at it?

Martinjus, any particular reason why we shouldnt polish the intakes? the vehicle is going to be webbered?

Joe924racer, what do you mean exactly by the flat top of the exhaust side port?

Thanks

dreamgts
_________________
2 PORSCHE 924 (CURRENT PROJECTS)
2 CLASSIC CORTINAS (FINISHED)
1 CLASSIC FIAT(FINISHED)
1 CLASSIC FIAT 132 2000CC(JUST PURCHASED)
4 SUV'S
2 SEDANS
1 OPEL PANEL VAN
WIFES SUZUKI ALTO

the_mad_electrician · Joined: 16 Nov 2009 Posts: 1073 Location: Central Georgia

Joes924Racer · Posted: Sun May 22, 2011 12:20 pm Post subject:

Ill put up a pic here shortly.
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1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

leadfoot · Posted: Mon May 23, 2011 1:05 pm Post subject:

Use the intake/exhaust gasket as a guide and scribe a marking around the inside circumfrence
Next using a cutting burr trim to around half an inch to inside the runner to get most of the edge cleaned
Then blend this into the runner about another inch in so tha the transition is smooth
on the intake pay particular attention to the roof of the runner as rhis has a casting ridge that will need to be smoothed, use your fingers to feel out the lumps and bumbs and then after youve finished with the majority of burr work use an 80grit flap wheel to give the whole runner a clean
On the bowl side theres not much you can really do, trim around the valve stem guide and casting to get this to a nice point and again smooth the ridge along the inside radius.
Exahust ports are a little better so again blend the gasket side and give the runners a tickle
The do your manifolds, and wear goggles when you do the cast iron manifold as they get in your eyes and it a trip to the doctors to get the filings out
All an all without a flow bench you cant really do much
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1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...

Lizard · Posted: Mon May 23, 2011 6:27 pm Post subject:

Head porting is a trade, if you dont know what you are doing with airflow, then you will likely make it worse.
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3 928s,

simsport · Joined: 06 Nov 2002 Posts: 573 Location: UK Warrington

Burr tools can go bang, and alloy in the eye is no joke, wear the right gear!

cheers
Simon
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Blown is always best!

gegge · Joined: 27 Jul 2007 Posts: 1124 Location: Sweden

leadfoot · Posted: Wed May 25, 2011 7:48 am Post subject:

+1
I followed a really good article in street machine that was produced by a head porting shop.
As I said I would consider what we can do as "head porting" is basically port matching of the gaskets and a clean up of the runners to remove restrictions.
If you stick your fingers inside the runners it doesn't take a genius to work work out where there are inconsistencies in the casting process.
You might also check out the pricipal of having a reversion dam when doing the exhaust ports.

Somewhere in here there's a post on 931 head design where the concencus of most board memebers was actually a redesign of the intake runner completely.

The easier method is to change pistons and use a 931 head, ala D prod, but you will end up with an interference design staying with the N/A application and have to use a custom piston to get the right compression height.
Time to get out the engine calculator if going this route.
Stu
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1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...

gegge · Joined: 27 Jul 2007 Posts: 1124 Location: Sweden

David Vizard has written a very good "porting school" that I do recommend reading. Just google. It does cover the basics as well as advanced stuff. Everything dynotested, not only with flowbench.

There is another very good forum - Speedtalk. Highly advanced indeed but educational and free.
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Carl Fredrik Torkildsen

924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs

dreamgts · Joined: 29 Dec 2009 Posts: 504 Location: malta

The porting is going to be done by a pro, he immediately noticed the restrictions which when compared to what is posted here seemed to be correct.

He was a bit concerned since he did not know the amount of metal he could grind off since he has never done a 924 head before and also had no measurements etc.

I beleive this info was not available for a number of years. I told him I might be able to get him some sort of diagram, which I did, from a thread posted by endwrench about the subject showing a cott out diagram of the head.

It seems he has a better picture now of the head structure and design. I think his main concern were the water jackets. If its not too expensive We might attempt to air flow test the head, if we do I will post the results.

Thanks all for contributing.

dreamgts
_________________
2 PORSCHE 924 (CURRENT PROJECTS)
2 CLASSIC CORTINAS (FINISHED)
1 CLASSIC FIAT(FINISHED)
1 CLASSIC FIAT 132 2000CC(JUST PURCHASED)
4 SUV'S
2 SEDANS
1 OPEL PANEL VAN
WIFES SUZUKI ALTO