Datsun Roadster Forum-311s.org

Hi All-

Hope I can ask this question without being to confusing. I added two Weiland Air Cleaners to my 1966 SPL311, 1600. These are the air cleaners that use a washable foam element. The type that I had purchased are listed at allowing CFM of air flow of 400. I connected the breather tube from the valve cover directly to the rear air cleaner.

My question is do you think that I should have enough suction to vent my motor? Someone mentined that I should vent it into the manifold, but I didn't think that was correct.

Thanks in Advance.

Ivin --

Pictures are at: http://community.webshots.com/scripts/e ... ity=DTijjK

Sorry:

http://community.webshots.com/user/ivin100

Ivin

I've seen setups where ppl don't pipe it back into
circulation. They put a breather on the valve cover instead.

Is this an OK practice?
I imagine the engine should burn better like this.

Ivin,

That setup should work just fine. Those are pretty nice looking air filters. The reason you need the vent hooked up to some sort of engine vacum is to scavenge the crankcase pressures. I used a K&N filter on the breather tube as KT mentioned and had a small but annoying rear main leak. I am using a foam ITG filter on the purple beast and plumbed it like the stock air claner so the vent gets drawn into a tee by both carbs. I am running K&N 240Z style round filters on my latest project. I put a PCV valve in the intake right behind the rear carb. I have it connected directly to the vent tube on the valve cover. So far so good. I can take a picture of that setup if someone likes.

Steve

Ivin,
I notice in your setup, that only the rear carb pulls the
vent gases??
If so, I imagine that the rear 2 pistons won't burn as strong
as the front 2. The front 2 gets more 'Air', whereas the rear 2
are burning 'used' air.
You don't have any weird idling problems??

Recycling of these gases is for smog reasons. I've read
it also keeps piston/cylinder tempertures down.
Just curious, do guys running the breather notice higher
engine temps??

I like S Allen's way of plumbing it into a Tee.

S Allen,
why would putting a breather on cause a rear main leak?

I'm considering putting a breather on myself. I notice when
I don't recirculate the gas, the engine idle noticeably picks up just a bit.

There is an option that has not been discussed. You can get a valve cover without the vent connection and get a road draft tube. Remove the odd sized freeze plug on the rear of the engine above the starter and install the road draft tube. Put a ventilated oil cap on it and you have what the 1500s and early 1600s ran. worked fine - just causes a little more noxious fumes to be released and perhaps a little oil dribble on the road....

I don't notice anything out of the unususal with my car. I don't have a breather (just the open vent on the valve cover) I don't see any change in temperature either. Infact, my car runs a bit on the cool side. I have never seen it even get close to being hot. I have been thinking of running a hose out and down the right side of the engine as a breather hose so it will vent into the airstream below the car.

Will

KT,

The vent has nothing to do with cooler running cylinders/pistons. That is the job of the cooling system. Sid's way would work. It was done for years that way. As a matter of fact when they were building my stroker they wanted to leave out a freeze plug so I could put the draft tube in. The draft tube is already close to the crankcase as it is in the block. The valve cover vent is not and needs some engine vacum to siphon off the the excess pressure. Many people including myself have tried the cool looking vent filter. You might get away with it but do not be surprised if you see a puddle of oil under your car. No filter is just as bad i.e. venting to the air. It still needs some vacum to vent properly. I do not think Ivin will have any problems with one carb running richer or poorer than the other. Please let us know Ivin if it does cause problems. I have done the same thing on my latest stroker intake but with a PCV valve in the intake of the rear carb. If it causes me problems I will be sure to let everyone know. My 3 cents on the subject.

Steve

I am going on sheer prudence to aswer this question.

I on the safe assumtion the Nissan engineers prior and after the DOT laws knew what they were doing by not using a breather and connecting the hose to the carb intake.

I wouldn't to 2nd guess them without emperical data.

However the 1600 wasn't as overly engineered as the 2000, but even the 2000 has the same conneciton to the carb intake.

Just my 2 cents.

What I took from this article is that if you use recycled gases,
the engine temp is reduced, maybe not by much, but nonetheless.
Again, this all pertains to smog:


The Exhaust Gas Recirculation (EGR) valve is used to send some of the exhaust gas back into the cylinders to reduce combustion temperature. Why would we want to do this?

Nitrous oxides (nasty pollutants) form when the combustion temperature gets above 2,500 degrees F. This happens, because at such temperatures, the nitrogen in the air mixes with the oxygen to create nitrous oxides. Did you ever have two friends that were fine by themselves but just awful when they got together? Well, our good friend, the sun, is just like that. When it's sunny, the nitrous oxides from the exhaust get together with the hydrocarbons in the air to form our not-so-good friend, smog. That's when the EGR valve comesin handy.

By recirculating some of the exhaust gas back through the intake manifold to the cylinders, we can lower the combustion temperature. Lowering the combustion temperature lowers the amount of nitrous oxide produced. Consequently, less of it comes out the tail pipe.

There are two types of EGR valves. One operates through the use of a vacuum, and the other operated through the use of pressure. Both types allow the exhaust gas in to lower the combustion temperature when it gets too high.

PCV Valve
The process of combustion forms several gases and vapors; many of them quite corrosive. Some of these gases get past the piston rings and into the crankcase. If left in the crankcase, these substances would cause all kinds of bad things (rust, corrosion, and formation of sludge), so they have to be removed. Back in the old days, they used to be dumped out into the atmosphere through a tube. Once we realized what a problem pollution was in the sixties, the PCV (Positive Crankcase Ventilation) system was developed to take the place of the old "dump tube."

The PCV system uses a hose connected between the engine and the intake manifold to draw these gases out of the engine's crankcase and back into the cylinders to burn with the regular fuel. The only problem to solve is how to keep these gases from going willy-nilly into the manifold and upsetting the required air-fuel ratio. The solution to this problem is the PCV valve.

The PCV valve controls the release of crankcase gases and vapors to the intake manifold. The valve is kept closed by spring action when the engine is at rest. When the engine is running normally, the low vacuum it creates allows the valve to open and release crankcase vapors and gases into the intake manifold for burning. If the engine is idling or you are slowing down, the vacuum level rises and pulls the valve plunger into the valve opening. This partially blocks off the opening so that only a small amount of vapors and gases can be drawn into the intake manifold.

One really comforting feature of the PCV valve is its behavior in the event of a backfire. If your car backfires in the manifold, the pressure makes the spring close the valve completely. With the valve closed, there is no chance that the flame can move into the crankcase and cause an explosion.

Wow!! As usual...some very good discussions. I like the idea of a T-fitting and I actually went to the hardware store this evening and picked one up. I will go to get some additional hose tommorow. I am currently using some rebuilt carbs and although they seem to run fine, I do have a rough idle. I'll have to see if the tee helps with that. I'll also re-check my balance between front and rear carbs. I'll keep you all posted.

As for the PCV valve,.... that seems very logical. Are any of you 1600 Roadsters using a PCV valve?

As Always, Thanks Ivin