Engine Breathing

[pgp001]

I have been thinking whether or not I should be changing the engine breather set up on my 1968 Traveller in order to minimise the oil escaping from the scroll seal.
The current setup is a hose from the rocker cover into the air filter housing
There is also a metal pipe from the front tappet chest cover dropping vertically downwards towards the sump, this does not seem to be correct as the ones I have seen mentioned are usually bent into a hook shape.
I have seen the photo's of cars set up with a PCV valve and the chimney pipe canister type of tappet cover, but I believe these were for the US market ?

So I am wondering if I should get hold of a chimney type tappet cover, but connect it straight onto the carburettor, I would need to get a different carb as mine does not have the connection point on it. It is my understanding that I would also need to block the rocker cover breather pipe and change the oil filler cap to one with vents in it.

Various opinions have been expressed over the years on this and other forums, what I am after is a definitive answer as to the benefits of this modification preferably from someone who has actually done it and can tell me the results. Or indeed if I would be wasting time and money.

Thanks
Phil

[ianmack]

My 1970 car has the rocker box pipe to the air filter and the bean can type breather on the tappet cover. During the winter with cold weather and short journeys it tends to form mayonnaise in the rocker box which in turn blocks the breather, the outlet from the rocker box being quite small, so the sludge becomes self perpetuating.

I have just removed and cleaned the box, but at a pinch the breather could be cleared with air. I think the standard breathers are adequate if kept clear and I certainly wouldn’t consider the expense of a new carb for a possible minor benefit.

[philthehill]

The two main causes of oil leaking from the rear return scroll are

1.............Blocked engine breather system.

2.............Worn main bearings especially the rear one.

Have a look at the MOSS link for breather system details.

https://www.moss-europe.co.uk/shop-by-m ... minor.html

There were at least a couple of types and shapes of breather pipe from the front cam follower cover. Straight down and hook type.

I agree with Ianmack - quite a bit of effort and expense especially if you fit a PCV valve system.

I would make sure that what you have is serviceable first and go from there.

You may spend the time and money and still the engine weeps from the rear return scroll.
Phil

[Monty-4]

On changing from a HiF38 with the breather connection back to HS2 carb(s) I was able to pick up a PCV (or "emissions") valve cheaply so went the tappet chest breather with canister -> valve -> intake manifold route. It reduced the oil consumption on my old tired engine significantly (went back to just burning it!), and now with the rebuilt motor it's hardly used a drop in 2000 miles. I do see it as a worthwhile mod and like the idea of venting fewer hydrocarbons into the atmosphere too.

That said, as the above posters mention - if it ain't broke and you can't find a cheap PCV valve, don't fix it?

[pgp001]

OK Just a quick update.
I have finally carried out the mods to the breather system as outlined in the original post.

I already had enough parts to build a spare SU carb with the breather port on the side, so I rebuilt it using all new parts such as throttle butterfly and spindle, new main jet and needle, float valve, spring etc.
I ran the car with that fitted but the breather port capped off for a while just to make sure it still ran OK, it actually ran much better as it turns out, the original carb had a well worn spindle that was allowing air to leak past and upset the idle mixture.

So a couple of days ago I took the final step of adding the cannister breather cover and connecting it to the carb. I could tell straight away it was going to be an improvement because with the oil filler cap removed it will now suck your hand onto it whereas before it was just pulsing with no vacuum.
It had become normal to expect a puddle of oil dripping from the split pin in the bell housing after every journey, this puddle was on average about 4" diameter after only a six mile journey. Now after doing this modification there are maybe three or four drips at most.
I think that is a fairly conclusive success.

The other thing I found, whilst doing this I took the rocker cover off to check the valve clearances, and there was a good 1/4" thick layer of mayonaise inside it, I am hoping that now I have some air flow in through the breather cap that this will not happen in future, time will tell.

I was a bit sceptical about this breather mod, but if you too have a car that likes to leave its mark, I suggest you give it a try.

Phil

[IslipMinor]

Phil,

Mayo in the rocker cover indicates that the engine is not spending enough time at full operating temperature. What thermostat are you using? I would suggest a minimum of 82°C all year round. Also keep the heater circuit open, so that there is a good flow of water around the back of the engine.

The engine oil should be a good quality 20w/50 mineral type, with a quality rating of SJ or higher. What are you currently using?

What is your typical journey pattern? A 10 mile motorway or dual carriageway run at 60-70 mph fairly regularly should keep the mayo away, as well as flush out other contaminants from the oil system. Do you have an opportunity for a good long run at motorway type speeds? If you do it would be worth draining the oil immediately afterwards, as it will be at its least contaminated.

[pgp001]

Hi

I think you are right about the short journeys, most of its life during a normal week is doing journeys of around six miles at a time.
Maybe on a weekend we venture a bit further maybe 30 odd miles or so.
Next week we are doing a good long 100 mile each way trip to the east coast for a long weekend via Sledmere House rally, so that should help things a bit.

Whats a motorway by the way ?

Phil

[oliver90owner]

To back up what Islip Minor indicated. I bought a very shiny aluminium rocker cover and fitted it to my ford engine (back about 50 years ago). It did not stay on long and was sold on to someone else who, like me at the time, thought it was pretty. Removed because it was soon lined with creamy gel, while the usual rocker cover was not afflicted with that problem. Fords, back then, breathed from a simple pipe to atmosphere.

This water clearly comes from piston blow-by of combustion gases (unless the engine has other serious problems). Worn bores,or poorly seating piston rings, will exacerbate any such problem.

[philthehill]

The oil used also has a bearing on the amount of mayo to be found in a rocker cover.

Back when Morris Minor 1000s were in current production it was found that Duckhams Q20/50 produced a considerable amount of mayo in the rocker cover whilst Castrol 20/50 did not.

If the rocker cover is kept cold it will condensate and form mayo inside the cover - a one time mod was to fit a plate in front of the rocker cover to keep the cold air off it so as to reduce or eliminate mayo condensate.

The alloy rocker cover will dissipate heat quicker and may allow mayo to form easier.

I have had alloy rocker covers on my engines for many years and I have always use Castrol oil and have never suffered with Mayo.

Phil

[pgp001]

I dont know for certain what oil is in the engine at the moment as I have not done an oil change since I bought it in February, and the oil on the dip stick still looks very clean.
The chap I bought it off had a few cans of Halfords Classic 20-50 in the garage, so I assume that is what will be in it. Do you have any experience of that brand ?

Phil

[oliver90owner]

Phil,

Regarding oil supplier, you may be correct.

Back then I may well have been using ‘duckman’s’ oil. I was not aware of any ‘mayo’ problem with any particular brand back then. I most certainly would not have changed the supplier at that particular point. I would only have removed the alloy rocker cover and replaced it with the original. From nothing to a problem and back again. It was only on for a short time. I could not be doing with a mess like that!