924Board.org

[ideola]

What I am saying is that the image of the head isn't really useful without looking at how the manifold attaches to it, and the angle of entry of the intake runners. You can't fill up that green area without creating a blockage of flow for the stock manifold (and, FWIW, the Webber manifold adapter, which is designed for the NA head based on the NA manifold). So if you plan to raise the floor of the intake ports on the head, you need to engineer a new solution for your intake runners, whether you use the stock intake manifold or plan to run carbs.

The point being, the inferior design of the angle of entry on the intake runners is a direct result of the space limitations and the engine being canted on a 45 degree angle and the low rake of the hood. I've often wondered why Porsche didn't design the manifold such that runners came up at a steeper angle and attached at the top of the plenum, with the throttle body positioned at the front of the plenum rather than the side. Imagine a 2.0L version of the 924S/944 intake manifold. This would have greatly improved the angle of entry on the intake runners, and the side benefit for us '31 owners is that it would have made FMIC plumbing much more convenient.
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erstwhile owner of just about every 924 variant ever made

[dreamgts]

The angle of the intakes and the manifold have definetly got to be taken into consideration as you say. My mech is aware of this and has stated that by filling the green area we might interupt this.

He adds that one of the solutions might be to skim the inlet manifold facing to correct the angle which would make the intake move in an upward angle accordingly. We have already done this on a Ford x-flow engine in order to match the ports. it worked perfectly. Maybe the N/A head manifold would need some other alteration, will just have to see.

So does anyone consider filling the green area behind the valve guide /stem to be accurate/close or more of a better solution?

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

[fiat22turbo]

I have a set of sidedraft manifolds for another vehicle that had the same issue as Ideola is describing. It looks like the solution they employed was to fill the bottom of the intakes to smooth the transition with some epoxy filler.

This intake was used on a turbocharged 2.2L 4-cylinder blowing through the webers. Made about 150-160hp at 5-7psi without an intercooler (essentially the same as the stock fuel injected version of that motor) With better fuel control it might have made more power since the intake design was actually better with the side drafts versus the stock "log" intake.

Considering the work I had to do to get the sidedraft intake to mate up to my motor properly (slotted mounting holes, lots of port matching) I'd say you would have to work hard to make it worse than when you started

One final thought on correcting the intake path: Perhaps instead of cutting the mounting flange down, maybe build an angled shim piece to fit between the intake and head? That could give you more room to transition the intake path without weakening the mounting flange and potentially causing leaks.
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

[the_mad_electrician]

[fiat22turbo]

Heh, I do have a Mercedes supercharger available for sale

I tried to find a picture of that setup, but that was a long, long time ago. I do still have the intake bonnet for the carbs and the intake manifolds (plus a spare set of DCOE ITBs, heh)
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

[the_mad_electrician]

Really? Hmmm. That could be interesting.
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81 924 N/A

2004 Ranger "Edge"

2005 Mazda 6

[dreamgts]