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Posted by: Porsche Rescue Apr 29 2003, 08:35 AM

Now that I have a handle on Weber fuel plumbing, I am moving on to oil vapor hoses. The engine I am installing is my first with carbs. Can someone tell me what the two small open pipes beside the intake manifolds are for? I assume they are on stock FI engine and I just never noticed them.
I believe I need some sort of vapor cannister (have seen one made by K&N). Do I connect it to the plastic nipple at the oil filler and then to the two nipples at the manifolds? Is this a crankcase vent system? Is there a PCV valve needed? By now you can tell that I'm not real sure I know what I'm doing!

Posted by: tryan Apr 29 2003, 11:20 AM

my opinion, put filters on each vavle cover or feed them into one breather canister. hook the pvc/plastic nipple at the oil filler to the intake and jet accordingly. it's always good to keep a vacume on the case. (fresh filtered air into the vavle covers. nasty blow-by gets sucked into the intake.)

i hate gas fumes. i would hook up the charcoal canister as close to stock as possible.

most have three connections.

the tank. leave this one alone.

the air filter/ breather .you will need to have a barbed fitting on the breather/air filter that will not get in the way of your linkage. either side. make sure the hoses are not rotten in the fender wells or rocker panels.

a vacume connection that will purge the vapors while the engine is running ( alot of people just disconnect this stuff, but gas fumes kill me. i'm a diesel lover )

Posted by: Porsche Rescue Apr 29 2003, 11:41 AM

Tryan, thanks, but can we keep it a little more simple.
1.What are the two open tubes at the heads for? Air/fumes in or air/fumes out?

2. The plastic nipple at the oil filler is crank case vent?
Is it related to the tubes at the heads? I really don't want to vent the case into my carbs, and I don't see a connection on them anyway (Weber 40 idf).

Posted by: Brad Roberts Apr 29 2003, 11:50 AM

Jim,

Are you working on a 6 or a 4 cyl car ?? Our thread about the fuel setup had me thinking all along that you where working on a 6cyl car.

We bring all three together into a common "junction" heads/oil filler. The ideal situation would be to pull a vaccuum on the heads and the oil filler like the factory did... but since you have dual carbs.. this isnt going to happen. You will end up with a catch can of some sort that left over oil/vapor will accumulate into.

B

Posted by: Porsche Rescue Apr 29 2003, 12:00 PM

Brad,
Thanks. I am installing a 2.0 4cyl with dual Webers.
That is the car which came with the PMO fuel block/regulator. I have my eye on a real nice looking aluminum billet block with a breather. Sounds like you are saying to run a hose from all three places (each head and crankcase) to the breather box. Right?

Posted by: Brad Roberts Apr 29 2003, 12:03 PM

Correct.

I use a CB performance block.

I was fooled this whole time.. I seriously thought you where working a 6cyl car.. DOH!


B

Posted by: Mike D. Apr 29 2003, 12:34 PM

I thought the whole Idea was (in FI world anyway) that the crank case breather to plenium hose is a vacuum that draws clean fresh air into the heads via the two head port hoses into one, and that one into the air cleaner. IE: drawing cooler air over valve train, maybe assisting in running oil back down pushrod tubes, and/or just keep a good flow of air moving through the crank case. DON'T ASK IF IT WORKS, I don't know.
I've seen people with carbs put a T on the crank case breather and run it to the carbs. Not sure if that does anything either.

-Mike D.

Posted by: MarkV Apr 29 2003, 03:10 PM

So on my carbed 2.0 4cyl car there are vacuum ports on the tops of the air cleaners. The pass side air cleaner is connected to the factory PCV valve. The drivers side air cleaner is connected to the factory tee that connects to both heads. Seems like this would give you a positive flow of fresh air through the engine. Is there an advantage to running the air box instead?

Posted by: Brad Roberts Apr 29 2003, 04:10 PM

Air/oil is being pumped out of the engine by the backwards motion of the pistons (internal crank case pressure) If you block off ALL the ports from the heads/block.. it will leak oil like a MF'er. It will try and blow out of any seals that it can.

Racers run belt driven vaccuum pumps and pull 14 inches of vaccuum on the heads and block (if the engine isnt dry sumped.. dry sump setups will use one stage of the pump to pull vaccuum) This free's up HP by countering the internal pumping loses. We get the similar effect by running the stock 2.0 air cleaner. I would rather free up HP than have a "cone" style filter that doesnt allow me to pull some vaccuum on the heads/block.

The fan shroud has one fresh air port and the drivers side tin has a fresh air port... these supply air to the 2 black lines that run to the charcoal canister to help delute the fuel vapers. This is the only two ports that actually supply air... the rest are for out going air.

B

Posted by: Brad Roberts Apr 29 2003, 04:16 PM

One more thing... if you have a carbed engine that leaks and leaks... you now know why it leaks. We run a huge breather box with a radiator hose leading to the oil fill to properly vent the case. We pull it off to fill the engine with oil. Its angled back towards the trunk where our breather "box" resides.

B

Posted by: Gint Apr 29 2003, 06:13 PM