This post has come about for a couple of reasons.
Firstly because I wanted to discover what PCV is all about.
Secondly, how I could go about getting the factory functionality back from a motor that was stripped of its factory setup.

The first part wasn't too hard to do with the information readily available from plenty of sites. The more difficult bit for me, as someone with no real depth of knowledge about the mechanics of motors, has been what do I do, and where does it go.
I soon came the conclusion that there was little chance of being able to restore the engine back to its factory setup as the airbox, lower crankcase valve 'unit' and solenoid are not parts that are readily available, nor advertised for sale.

I then started having a closer look into the Forum as to what information there may be. I have cut and pasted those posts that I have found to be informative (to me). I hope I have done the correct thing in showing the relevant post and member details. I thought this may also be a useful thing to do to have something in one spot for those that may be wanting to start the same 'journey'.

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Thread - 3T/2TG Blowby

MWP 5/1/07

Having a vacuum in the crank case is always a good thing.
It does reduce blow-by by making the rings seal better, decreases oil contamination & helps prevent oil leaks from gaskets/seals/etc.

The is the setup you want:
cam cover -> pcv valve -> catch can -> inlet manifold.

Make sure the catch can is the type that has one inlet, one outlet and a drain bolt on the bottom.
The ones that have the air filter on top are useless.

The Witzl 8/1/07

I have my 18R-GE PCV system setup pretty much exactly as per the 2T-G stock system...


This means air is sucked from in front of the TB, thru the crank, out the crank vent and into the intake.... taking the dirty oil vapours with them.

This is how it was meant to be from the factory

Thread - TA22 2TG

w810sc 18/6/07

On standard original setups on the 2T-G, the valve cover breather pipe connects back to the intake unit, but if you have the Lynx Ramflow filters, the pipe simply connects to either one those. I just use a piece of plastic hose that points down towards the dizzy because i run ram tubes with socks.
The valve cover breather hole can be connected to a oil catch can or simply return it to the blocks breather on the side, or/with the combination of the catch can too.

Thread - A Few 2TG & Solex Questions
TheToyman75 3/3/16

The 2TG only has one breather on the Rocker cover (no PCV valve on the twin cam)

From factory this plumbs straight into the back of the factory Airbox. As others have mentioned, an Oil catch can is a good idea after you pass rego.

For now, See if you can borrow a set of the Ramflow air filters, these has a plastic block off in the base plate designed to take the engine breather. If you buy them new, they will even come with the plastic barb fitting to connect it too. Avoid buying them if you can - They are shithouse filters.

Thread - Oil Catch Can/Breather

TurboRA28 12/1/06

My understanding is the catch cans with the 2 pipes and no breather are designed to work like this..

1 hose from the crankcase vent or rocker cover
1 hose back to the inlet

MWP 12/1/06

People need to learn the theory of PCV:
- Removes gasses from the crankcase which can contaminate and shorten the life of engine oil.
- Puts the crankcase under a slight vaccum which helps prevent oil leaks and improves piston ring sealing.
- Stops nasty gasses being vented to the atmosphere.

Whoever came up with the idea of vented oil catch cans should be shot.
To me they look like someones simple way out rather than a well thought out solution.

Thread - How Do You Fit Up An Oil Catch Can

peedman 20/4/06

Run a tube frm the crankcase breather into one side of the catch can. Then the other hole of the can connect a tube that runs to your intake manifold where the stock breather tube was connected. Its that simple.

slide86 20/4/06

you can set it up so that it doesnt have the return into the air intake. this eliminates any crappy gasses from going back in to the intake and polluting the air/fuel mix.

its definetly not legal, but hey, what is these days. you can buy catch cans with an air filter on them that vents the gases to atmosphere, you have to empty the can of oil every now and then tho.

Big T 20/4/06

No it's illegal to have them venting to atmosphere... another downside is that you generally get an oily residue all over your engine and engine bay. Just plug it back to the intake.

oldcorollas 21/4/06

as with most mods, if you don't know why you need it... do you really need it?

catch can is a can that catches oil

it is NOT a must for modified cars. it is only needed when you have excessive oil coming from the rocker/cam cover vents. crank case breather should not be spitting oil

if you are not currently losing significant amount of oil, you don't need one, and it is just a wank..

TA-022 22/4/06

also and im surprised it hasnt been mention yet , the oily residue past backed to the intake will mix with fuel once it hits the cylinder and can lower octane ratings resulting in detonation.

note: you'd need a decent volume of oil passing back to the intake for this to actualy affect power. but any kilowatt is a good kilowatt!

For the love of a tractor engine: The life and times of the 18R-G

Rodger 22/8/08

The Pipe from the block is the one that needs the PCV Valve. It should connect to the balance tube in between the two manifold halves.

The OEM spacer has a groove or grooves arranged so the two barrels of each carb are connected and with help of engine vacuum it draws fumes evenly into each port from the block.

The second big pipe in the balance tube is for the Air Valve system and was plumbed to an electric solanoid valve and then to the air filter housing. This allowed a big gulp of fresh air to enter into the manifold at shut down to stop 18R-Gs from running on. The valve was mounted on top of the cam cover using those two M6 thread holes every cover has.

The pipe fitting on the Cam Cover is the fresh air inlet for the PCV system. Fresh air is drawn into the engine, combines with any oil and fuel vapours and gets drawn back out the PCV pipe to be burnt in the engine. It should be connected without a PCV valve to a filtered air source, such as the filter backing plate. Or it could simply have a small filter directly attached to the fitting. However a lot of Road User Authorities do not like to see that small filter and like the pipe to go somewhere.

If a PCV pipe is not connected or is blocked this Cam cover port is where all the blow by gases and excess oil ends up coming from. Hence a lot of engines have very oily filters or the engine is a mess.
If it is blocked or has another PCV in it and the block's PCV pipe is connected correctly then you create a vacuum inside the motor, which if good enough sucks more fuel past the rings and raw oil out of the sump which can really muck up fuel mixtures and foul plugs.

If you have Softmounts then there is nowhere for the fumes to be drawn into and any PCV system will not work as intended. So you would need to drop the PCV system. In this case make sure you run the Cam breather to a filtered catch tank.

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My crankcase (block) breather is blanked off and I have softmounts between the carbs and intake manifold. The only factory part I have been able to purchase is the pipe that fits to the intake manifold.

Considering the information detailed by Rodger in his above post, and using the only factory part that I've been able to obtain, I see the option as below. Not the most complete solution as nothing is included for the crankcase (block) which does seem to be an important part of the complete setup.

Run an oil hose from the cam cover (A in the photo below) breather to a baffled separator with 2 ports.
From the 2nd (out) port, run an oil hose and connect to both the balance inlets (B and C in the photo below).
Close off all remaining connection points on the intake tube pipe.

One thing I'm not clear on is if there is any benefit in having a PCV valve between the cam cover and baffled separator?

Any input/comment greatly appreciated that may assist myself and others in regards to the above. Please point out any errors/misunderstanding on my part, or editing required.

Pre April '73 setup

Post April '73 setup

Post April '73 setup

Mine at present