924Board.org

924-76 · Joined: 05 Jun 2006 Posts: 1489 Location: Ontario, Canada

Working on the weber 40 dcoe conversions and I don’t know what to do with the engine breather line that connects to the air box.
What you guys did with it?
Do you know if that line needs any sort of vacuum on it?

Chrenan · Joined: 15 Jan 2003 Posts: 3903 Location: Canada

Even with my CIS I run that to atmosphere. I'd rather lose the vacuum on the crankcase than have all the crap recirculated through my intake. I fully understand the benefits of keeping a vacuum on the crankcase, but I could care less. I don't have any running issues, however, I have a very fresh engine rebuilt a couple of years ago with low kms. On a tired engine getting rid of the crankcase vacuum might cause increased blow by?
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1987 951 - M193 Version for Japan

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

Yeah, no PCV can also cause rear main seal leaks - ask Porschev.
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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

924-76 · Joined: 05 Jun 2006 Posts: 1489 Location: Ontario, Canada

So, to be safe I should keep that line on vacuum?
Any recommend setup?
Any picture from any one who are running the weber would be appreciated.

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

When I had Webers on my 914, I bought nylon elbow fittings and drilled holes to take them in both air cleaner lids. I then teed it together and to the CCV.
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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

924-76 · Joined: 05 Jun 2006 Posts: 1489 Location: Ontario, Canada

What do you thing if I put a small filter (like a carbs full filter type) on the line and connected the line with the brake booster vacuum line.

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

You don't want to put manifold vacuum on the crankcase. Use the air cleaners or nothing as Chrenan did (at the risk of oiling your clutch).

If you use nothing, I seem to recall somebody (K&N maybe) selling a mini-air filter for your breather hose that looks pretty cool (but is entirely non-functional).
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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

924-76 · Joined: 05 Jun 2006 Posts: 1489 Location: Ontario, Canada

The line is presently attached to the air box behind the air filter.
The way that air box is designed, is that would be the same vacuum then at the manifold?

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

Nope, the vacuum behind the throttle plate is higher than behind the air filter.

If you want to get fancy, you can add a vacuum barb to the exhaust and pull vacuum that way. There are kits for this since you have to get the barb in the exhaust at the right angle and depth to work properly. Drag racer love the fact that it increases the vacuum in the crank case, helping the rings seal, among other things.
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

AppleBit · Joined: 16 Nov 2002 Posts: 1516 Location: Minneapolis, MN

i have docs on my website
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Classic British Sports Car Restoration v6 + v8 Engine Conversion Swaps

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