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brealytrent · Joined: 28 Dec 2008 Posts: 414 Location: Goldsboro, NC

This is more of a ponder than serious question, but what would need to be done to make an early car ('77) with '81 head on it be able to safely rev to something like 7500-8000 rpm and still be streetable? Would it even be possible?
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1977 Porsche 924 - sold
1980 Porsche 931 - sold
1984 Porsche 928 'S2' Euro - sold
2016 Ford Fiesta ST - sold
2009 Porsche Cayman

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11723 Location: PacNW

It would need to be precisely balanced, obviously, and need a serious upgrade to the fuel delivery system! Lightening the valve train would probably be beneficial as well.
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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

Lightened or aluminum flywheel.

Lighter rods and pistons. Possibly even a lightened and/or knife edged crankshaft.

Ported head and higher compression to flow enough air at that RPM

Higher lift cam possibly

Lightweight lifters, which may or may not require stronger valve springs.

Better intake and exhaust (header, side draft carbs or a larger plenum/throttle body)

The lifters are a problem on the street since they require dissasembly of the camshaft to adjust for wear.

Since you'll be pushing the engine pretty hard, a reversed cooling system isn't a bad idea either.
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

Fifty50Plus · Posted: Mon Sep 30, 2013 2:23 am Post subject:

The stock cam runs out of snuff at around 6000 RPM. It will rev higher but why bother. You will need a better cam profile to have fun in the upper ranges.
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1979 924 NA race car
1982 924 NA race car - Sold
1982 924 Turbo almost a PoS
1981 924 Turbo a real PoS, new engine
1982 924 Turbo nice body, blown engine
1972 911 E race car - going to Vintage
Various 944s to become IT-S race car

ideola · Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI

This combination ought to get you close:

Stage 3 cam.
Big Valve Kit (for lighter weight valves and stiffer springs to handle the higher lift cam)
Sten Parner solid lifters (for lighter weight and improved strength over stock lifters, which will crack above 7K RPM).

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erstwhile owner of just about every 924 variant ever made

daniel · Joined: 18 Jun 2009 Posts: 670 Location: Sydney, Australia

How would the standard bottom end go above 7000rpm?
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Over the top of skyline, total brake failure.... hit the wall at over 200 kp/h at the dipper, so anyone who has to brake for the esses is a pussy.
1977.5 Race Car, CAMS Group S Spec
1989 944 Cabriolet

ideola · Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI

I don't think the bottom end is the problem, although lighter rods, pistons, and flywheel would help with freer revving, obviously.
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erstwhile owner of just about every 924 variant ever made

daniel · Joined: 18 Jun 2009 Posts: 670 Location: Sydney, Australia

So what compression ratio is recommended with the stage 3 cam?
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Over the top of skyline, total brake failure.... hit the wall at over 200 kp/h at the dipper, so anyone who has to brake for the esses is a pussy.
1977.5 Race Car, CAMS Group S Spec
1989 944 Cabriolet