Evaporation control system

[Guest rick458]

I am replacing the twin flattops with a Holley 390, I am demoing the

stock fuel lines, and cleaning up the engine bay.

Has anybody Fabbed a charcoal Cannister for the rear of the car

and plumbed it to the triangular Vapor recovery thingie by the filler tube?

[Guest billyzbear]

There are two ways to handle this. One throw it away. The other is leave it and hook it up correctly. It's been a while since I looked at a 260z canister. There should be one hose that comes from tank or the triangle thingy your talking about, that comes from the back. There should be a big port like 3/8 size and above it a diaphram with a 5/32 port. The fuel in the tank has vapors coming off of it all the time. These vapors goto the collection thing then to the canister. As the 5/32 diaphram gets vacuum off idle it opens then the vapors are then purged from canister.

On the early 240's they didn't have a canister, the vapors were purged all the time. It had a built in restrictor.

Depending on the Holly you have it could have a bowl vent. You could use a chevy canister that has the extra port for it. It's a 3/8's port above the fuel bowl.

All in all it's a good thing to have on your car as it will not harm anything if working correctly.

[Guest rick458]

I had not thought of routing it back to the holley

 

I may try to fab a sealed cannister with activated carbon

run it off the triangular vent collecter and plumb that

onto the steel line running back to the front and then to a Carb port

I will be running the Cam cover vent to one anyway

 

that way I keep a clean engine bay and a cleaner world

[Guest billyzbear]

It would be some work to route all the hoses but ya you could do it. The problem with canisters is the diaphram goes bad and the engine could suck in fuel. You would need a vacuum pump to tell if the diaphram is bad and you could see the raw fuel by looking at the hose. Just keep it in the back of your mind if your car starts to act strange.

I will be running the Cam cover vent to one anyway

Are you talking about the PCV system? In all motors you have blow-by, air & fuel. The engine sucks this out with a pcv valve. The port on a L6 is by the front on the driverside about mid way on the block. The other end of the valve goes to manifold vacuum. On a 260z the pcv valve gets screwed in the intake manifold. You could use a 3/8 port on new manifold and use a chevy pcv valve from a 6 cyl nova. Since air is being sucked out of the engine air needs to be allowed in. The port on top of the valve cover goes to the air cleaner, a "closed" system. An "open" pcv system you could get a little K&N filter that goes right on top of the valve cover. If there is too much blow-by and the valve can't suck it all in some will go to the breather side. If you run without a pcv system your oil will get dirty real quick. In the old days they would hook the pcv valve side to a check valve in the exhaust. Blow-by is nasty stuff and can make a mess of your intake manifold and inside of head. This can be cleaned though. Just run some cleaner through port.

I live in Ca. and I smog cars and we need closed pcv systems here.

[Guest rick458]

I am planning on running a breather on the 1 1/4 port by where the air pump was and pulling via the Cam cover through a pcv valve and running that to the carb port (or is this a fatal flaw)

 

I was thinking a rectangular container full of carbon sitting next to and pulling off of the triangular vapor recovery widget by the filler neck.

I will feed into the top of the container and draw from a hose at the bottom

and pulling that via the carb port.

 

I am NOT recirculating any fuel back to the tank

 

Will it work? it SHOULD just pull vapor

[Guest billyzbear]

You got it backwards. The pcv valve should be down by where the air pump was and any good manifold vacuum source will work for the pcv valve.

 

I have never seen a canister designed like yours.

 

If I had to remove the canister from engine bay. I would route the port from the tank to a FACTORY canister. If I had the extra port on the carb for float bowl vent I would get a GM one with the extra port. Mount canister some where. Route the vent hose from tank to port marked tank on canister. Route one 3/8 vacuum line from manifold to port marked vac. Route one 3/8 vacuum line from carb bowl vent to port marked bowl. Route one 5/32 vacuum line from ported vacuum to nipple on diaphram.

 

You want less hoses? You could use a Ford canister. Route line from tank to canister. Now this could get tricky. You mite need a restrictor. First would try a 5/32 ported vacuum(off idle vacuum). If I needed less vacuum? They sell 5/32 restrictors at Napa. They are green and look just like a vacuum connector but with a pin hole in them. If it sucks too much it will get raw fuel.

 

You need to remember all pcv and vapor recovery systems are calculated vacuum leaks that are routed to fuel vapors.

 

 

Would your ideas work? Maybe. I'm not an engineer.

[Tony D]

What the stock 240 system did through it's diverter vavle was to allow pressure to build in the tank (say from expansion on a hot day) to a set pressure of water column pressure. It then discharged to the vehicle's crankcase.

While cuel got sucked out of the tank on a drive, the same diverter valve vould allow filtered air from the air cleaner back into the tank while driving along.

We just had a club member go on a drive after finally replacing all his vent hoses in the back of the car. He ended up sucking the filler neck flat! Come to find out for years he had been running the little vapor line up front with a nice sanitary vacuum cap on it, and with all the leaks in the vapor hoses, it never made any difference.

 

The Carbon Cannister used the Charcoal as the storage medium, until startup and that flapper valve opened to let it purge into the manifold. Similarly, the vapor return line to the back of the car did the same function on the vehicle when driving down the road: let air into the tank to keep a vacuum from being pulled as the fuel was pulled out of it by the fuel pump.

 

Keeping fuel system integrity is easy if you know how they test the tanks. A small series of check valves (I despise PCV valves, they almost universally leak!) works to keep the "test pressure" on the tank during a fuel system pump up at check time (if the garage actually has the tank adapter!)

 

If anything , the easiest way to make sure it all works is to simply relocate the carbon cannister to the rear of the vehicle. Some other vehicles have smaller cannisters that would make packaging easier, but "may not" adequately provide for enough storage capacity for vapors. This will have to be your decision. In many cases as long as it's all hooked up and in place, they will let it go through the system on a check. If only functional stuff is required, then mixing and matching components will make for easier packaging.

 

The vent line for the EVAP comes off the top of the phase separator annyway from what I recall, so as long as it's hooked up so that it only gets gasseous fumes, you should be fine. But for the effort of relocating it to the rear of the vehicle, sticking it out in the fenderwell behind the headlight, or in the back portion of the wing behind the wheel would be just as easy, and require far less custom tubing to be done.

 

I agree, all PCV systems are a metered vacuum leak, this is why it's important to let it distribute evenly to all cylinders! In many cases with total closure systems (Think ITB's with an IAC motor on a log) the PCV may need to be restricted by an orifice as small as .050" to keep from the high vacuum incidents (snap throttle closed) from sucking oil out of the crankcase and into the manifold! I have a Mitsubishi PCV that fits in the hole int he side of the block, it has an .063" orifice built in (sorry, been almost 15 years since I installed it, no model information or tech specs) and it distributes through a 1/4" line manifolded into each intake runner, off my 3/8" balance tube.

 

Hope this helped in some measure...

[Guest rick458]

Thanks for the info, lots to learn there

I was thinking the Carbon relocation would work

 

I keep hearing that you MUST not pull from the Cam cover

and breath through the bottom port.