31 replies to this topic

[RallyRed]

Hi mate,

I'm no expert, but my understanding is that the hole is for the PCV venting.

The second hole often goes to a 2 or 3 litre tank ( as you say).

 

The tank is often a requirement of circuit racing etc authorities, to catch any oil.

 

e.g from CAMS manual.....""if fitted with any crankcase breather that vents to atmosphere, then each breather shall be connected to a catch tank. (  tank capacity shall be 2 litres for up to 2000cc engine, 3 litres for larger engines" ( not the exact words, but that's the intent I believe)

[TerrA LX]

Hi mate,
I'm no expert, but my understanding is that the hole is for the PCV venting.

Just to clarify PCV stands for POSITIVE Crankcase Ventilation, catch cans, as suggested are not usually Positively Ventilated.
Positive Crankcase Ventilation in OEM applications is applied via Inlet Manifold Vacuum.

Without any photos of what the OP is asking I have no real way of confirming if the rocker cover is standard or modified in any way.

I do believe that no 186 left Holden with PCV.

[S pack]

Terry,

AFAIK oil catch cans still have to have a vacuum source to work.

Connect PCV to catch can, connect catch can to manifold vacuum.

 

I could be wrong but PCV was introduced in HK or HT series so 186 engines had PCV valves.

LC XU1 186 definitely had PCV.

[S pack]

OEM = Original Equipment Manufacturer.

 

Holden's did not come ex factory with oil catch cans.

Oil catch cans are an aftermarket item useful on racing engines but street engines don't really need them, they just give a certain amount of wank cred.

[Dr Terry]

Just to clarify PCV stands for POSITIVE Crankcase Ventilation, catch cans, as suggested are not usually Positively Ventilated.
Positive Crankcase Ventilation in OEM applications is applied via Inlet Manifold Vacuum.

Without any photos of what the OP is asking I have no real way of confirming if the rocker cover is standard or modified in any way.

I do believe that no 186 left Holden with PCV.

What you say about racecar set-ups is correct. They usually don't involve manifold vacuum & simply vent directly into a catch can.

However most 186 engines did leave the factory with PCV.

Early Red motors up to mid-67 (149, 179,161 & 186 including X2 versions) had a draught pipe, shaped like a walking stick which ran out of the rocker over.

When the 186S was introduced it had Holden's first PCV setup & the then current 161 & 186 engines soon followed. So late HR & then all HK, HT, HG & most HQs used the same basic PCV system.

In late 1973 they changed to a 'sealed' PCV system. The only change here was that the vented oil cap disappeared & the rocker was vented into the air cleaner, for its fresh air supply.

Dr Terry

[S pack]

Plenty of info available if you Google.

http://torquepost.wo...w-how-the-work/

I noticed that the XU-1 on you tube has hoses from the inlet manifold that run into the brake booster?

Yes, Master Vacs (brake boosters) require manifold vacuum to operate.

[hanra]

On the subject of rocker cover holes. What could these be off? They have no holes.

[S pack]

Early 253/308 (HT & HG Holden)

The breather cap fitted onto the oil filler tube that lead into the timing cover.

The one in your pic with the oil cap hole would be off a HQ or later.

[RallyRed]

........not sure if I've missed something here?

the O.P. was asking what the holes were for?

I'd imagine if it was a 'hole' then we assume its a factory OEM type cover.

The 'hole 'is for the PCV.

Once he asked what the "holes" are for...I would assume its an aftermarket fitting

.

Not sure I've seen many cars with both holes going back to the inlet manifold, to get the vacuum?

Thus I assume the 2nd , or both, hoses  go the catch tank.

Most tanks Ive seen / got pics of, don't also connect to the inlet....the ex engine gases just vent via an elcheapo filter, to atmosphere.

 

p.s. one assumes that the oil filler cap hole, is not part of this question.

 

Anyway, like I said...I'm no expert.

Attached Files

•  oil catch small.jpg   227.88K   5 downloads

[S pack]

The OP has an aftermarket alloy rocker cover to suit a red 6. It will have 3 holes in it just like a OEM pressed steel holden ADR 27 rocker cover.

There is no compulsory requirement to install a catch can because you have an aftermarket rocker cover.

 

This pic is from Heath's UC build thread. This looks like it would be the rocker cover the OP is talking about.

 

Only problem is these covers do not come with baffles. The baffles prevent oil splash being sucked up into the PCV.

Heath has wisely made and installed baffles.

[TerrA LX]

Not sure I've seen many cars with both holes going back to the inlet manifold, to get the vacuum?

I can only assume what the OP is asking untill I see a photo and clarify exactly what it is they are asking, to answer your question, 3 holes would be;

A; OEM style.
1. filler cap hole.
2. hole for PCV, hose to manifold vacuum and
3. hose from the air filter to rocker cover for fresh air thru the motor to the PCV and to vent when the system is over pressurised like at full throttle.
This system vents internally to the air filter and is a sealed system as such.

B; Race application. System vented to atmosphere.
1. oil filler hole.
2. hose to vented catch can.
3. hose to vented catch can.
One or two catch cans can be used depending on their size and location.
This system is not under vacuum from the motor and therefore is not positively vented, it relies solely on the pressure in the crank case to expire.
This system is not vented to the air filter and is not a sealed system.

c; combination of above - sealed catch can to meet ADR27 and ADR 27a applications.
1. filler cap hole.
2. hole for PCV to to the catch can (sealed, no vent to atmosphere) then to manifold vacuum and
3. hose from the air filter to rocker cover for fresh air thru the motor to the PCV and to vent when the system is over pressurised like at full throttle. A second catch can can be placed in line here but must also be sealed, ie not vented to atmosphere.

[TerrA LX]

I must state that combination C is not a very easy system to balance, you have to have good flow thru the catch can if you have one on the vent side or you risk over pressurising the motor.

I have seen in some photos that they have hoses coming out and going into some sort of fabricated stainless  steel box with a breather of some kind.

This is what we refer to as the "catch can".

[TerrA LX]

However most 186 engines did leave the factory with PCV.

When the 186S was introduced it had Holden's first PCV setup & the then current 161 & 186 engines soon followed. So late HR & then all HK, HT, HG & most HQs used the same basic PCV system.

In late 1973 they changed to a 'sealed' PCV system. The only change here was that the vented oil cap disappeared & the rocker was vented into the air cleaner, for its fresh air supply.

Dr Terry

Cheers, I'm a 70's kinda guy, I could not remember if the earlier motors had them, thanx for clarifying.

[RallyRed]

good info.

[S pack]

Glenn,

 

Your 186 in a LC Torana does not need the third hole,  just the rear PCV hole and the oil filler cap hole. The third hole is for ADR 27 (Closed Positive Crankcase Ventilation) which you do not need to comply with.

Why do you believe you need a catch can?