G'day,

I've got a 1963 850 with a heavy breathing problem from the tappet chest cover and looking for any suggestions on how to solve the mess it's making please.

The engine was fully rebuilt when the resto was done and not long after it was on the road, there's been some oil dripping from the chest cover. Being an early motor, the outlet of the cover just points directly down, instead of going up and then down as per later models. I've attached a pic of the motor showing the current chest cover as well as a pic of some spare later model covers that I have.

One option I have is to fit a later chest cover. I understand that the covers can be changed while the motor is in the car (with a fair degree of difficulty I believe) but I think access wise, I would find it difficult to do as working crouched over in the engine bay or any length of time doesn't do the back any favours now. I'm also not sure the newer covers would fit clearance wise with the extractors I've got. I don't want to end up in a worse situation if I can't get the new cover fitted or clean off the old cork gasket properly. I don't want to pull the motor out either.

To keep the oil off the motor, I've had a piece of heater hose connected to the chest cover and run this down just below floor level. The passenger side floor is now well rust proofed and I'm getting a bit of oily residue on the rear as well.

I understand the heavy breathing is a result of compression getting past the rings and I don't want to do another rebuild so my options are to leave as is or find a way of minimising the mess.

An idea I've thought of is instead of running just a straight piece of hose from the chest cover, I'd insert a T piece in the hose up near the outlet of the chest cover and then the hose running from the bottom of the T down to floor level would have a tap on it and the side part of the T would either just vent to atmosphere. Given that the chest cover outlet only points straight down, it's no good running the hose up to the air cleaner as any oil in the hose would collect in the U part and effectively block the outlet.

With this setup, the oil should run out of the chest cover and then straight through the T piece into the closed off length of hose. The side piece of the T would allow for all pressure venting. I'd drain the hose as required.

Do you blokes see any problems with this idea and do you think it would work?

Thanks Rocky

Tony Cripps technical article on crankcase breathing (number 12 in the list) may help. He is not a fan of catch cans.

https://www.leylandaustralia.com.au/articles.htm

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ex-NSW Police 1970 MK II Cooper S
VMCI #43

You are better off creating some negative pressure in the crankcase via the carb intake and letting the engine consume its own gasses. It will also reduce the possibility of oil leaks elsewhere.
Hose from the cover plate to the carb side of the butterfly and a vented oil filler cap.

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Cheers Dave.

There are a lot of different ways to sort the breathers and some work better than others

If you have a “open air” or “atmospheric” breather system as per your early 850, then the more open breathers you can fit the less pressure it will build up. You can have a vented oil cap and a vented rocker cover which can help. You can route the gases into a vented catch can if you don’t want to make a mess. The main downside to this system is the smell & you’ll always have pressure in the crankcase

The next system where they fed the breather hose to the air filter case is a little better, but there isn’t a lot of suction on the hose


The PCV system works well too, but it can be a little temperamental if you have any extra air entering the system as the PCV is in the manifold post carb. As the PCV sucks out the crankcase gases it reduces the smell and other leaks


The later CCV port on the side of the carb is the easiest system and like the PCV it sucks out the crankcase gases.

Some of the later HS2 carbs had a spacer between the carb and the air filter with a connection for the breather, these would give a similar result to the CCV port


With a PCV or CCV system you can also use an inline catch can, which gives all the benefits of the factory system, but it catches a lot of the oil and water vapour before it goes into the engine. I had a setup like this on my old 998 & HS4 carb and it was surprising the amount of gunk it caught

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The pipe on your car is where air is supposed to enter. Even in early cars where the pipe is crimped, there is a slot in the crimp to allow for air entry. The back of the side plate should have a baffle on it to prevent splash going down the pipe. The suction is provided by the rocker cover vent pipe which is connected to the air cleaner. It is important that the correct oil filler cap be fitted. In your case, it should be a non-vented sealed cap. Those black plastic caps look similar on the outside, but the non-vented cap has a short neck, while the vented type have a longer neck with wire mesh inside. The pipe to the air cleaner also has to be in good condition and not clogged with oil soaked rubber debris. The whole idea is to create a gentle flow of air through the crankcase, not to put the crankcase under vacuum.

Thanks everyone for your replies - all terrific info and now I know how the system should work. I thought (in error now I know) that the breather from the rocker cover was like the ones on early Holden red motors which were just bolted down the side of the motor and vented to atmosphere. As such, I thought that as long as there was some sort of connection between the rocker cover and the air cleaner, it would be ok.

Now I know that the air cleaner is supposed to suck on the rocker cover pipe and create a suction, I know of at least one problem with my current setup. The fact that oil is coming out of the tappet chest cover would indicate that either the baffle is not in place or maybe that there's too much crankcase pressure which is forcing the oil past the baffle. Either way, there's a fair bit of oil coming out.

I've attached a pic of the current air cleaner setup. I'm running a 1 1/2" SU and the metal air cleaner body. This is obviously not original to the car and as you can see, there's bugger all room between the outlet on the rocker cover and the inlet on the air cleaner and as a result, the rubber hose doesn't fit neatly on the air cleaner end. I'd reckon it's not doing much sucking.

To add a bit more info about the oil coming out of the tappet chest cover, when I was playing around with the timing a few weeks ago, I had the air cleaner off so I could adjust the revs. I ended up with quite a patch of oil under where the hose on the end of the pipe finishes. Obviously no suction at all out of the rocker cover so the pressure had to go somewhere I guess.

I'll go and see if I can find a heater hose with an appropriate bend in it (or a bit of flexible hose perhaps) to connect the rocker cover to the air cleaner and make sure the hose if sealed properly.

With my setup, do you blokes have any other suggestions as to how I fix the problem if I can't find the right bit of hose?

I'll go and have a look in the spare parts bin and see if there's any carby adaptors like the one in Timmy's pics. I've also got another plastic air filter body that I could play with to add a better location for the hose and I've also got a pancake type air cleaner that I bought but didn't use.
It's a PF102A
https://www.minispares.com/pf102a-foam- ... air-filter

Thamks Rocky

There may (should) be a larger brass tube stub on the sidef the carb between the carb and the inlet ,anifold which would create the necessary suction.





With a vented oil filler cap you can connect the breather to the port indicated.

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Cheers Dave.

If you put a bit of welding wire up the tube it should only go as far as a couple of mm into the space behind the side cover before hitting the baffle. If it appears to be going all the way inside to the tappet chest, then that's a problem of course. That oil filler cap looks like a sealed one (I think the vented ones have a message on them to change every so many thousand miles). Theoretically, your set up should work as shown if the baffle is there. On a standard 850 with metal air cleaner housing, the passage into the air cleaner inner is reduced to 5/32". This has obviously been "well designed" and the small orifice at the aircleaner end must serve to increase the velocity of the air stream there. On that large plastic air cleaner, the drawing does not show this orifice so perhaps this has something to do with it. You might also consider that there is a high pressure oil gallery to the rocker shaft going up through the head gasket at near the side cover top left side and oil can seep out and run down the outside of the block.

G'day Dave,

I had a look on the carby and there is what looks like a 1/4" brass tube on that side of the carby but not in the same position you show on the pics. It's currently got a rubber cap on it to block it off. It's further towards the manifold than the ones in the pics. I can't remember what this is for as it's 5 years since the bloke who did the carby up told me and as I wasn't using it, I dropped that bit of info out of the memory bank

Is it the same connection and if I was to go down that path, could it be used?

On a different note, I've got a spare angle adaptor thing that bolts onto the back of the carby and is where the air cleaner gets bolted to and seals. I was thinking I could tap a thread in there and screw in a nipple to hook a hose onto from the rocker cover. Would that work you reckon?

Thanks Rocky

Yep the one with the black blank cap is it. Run a pipe from there to your breather and make sure you have a vented oil filler cap. This way the carb will draw any fumes out. It is still a good idea to have a baffled breather. You can put a filter on the rocker outtlet or block it off.
You may have to adjust the mixture slightly as well.

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Cheers Dave.

Thanks Dave.

I'm thinking of fixing up the connection between the rocker cover and the air cleaner first to make sure it's sealed ok as I don't reckon it has been. I'm also wondering if the main air intake on the metal air cleaner I have is bigger diameter than what would have been on the standard one for the 850 with the 1 1/4" carb? Just thinking that if the main air intake is larger on the one I've got compared to the standard one, then even with the rocker cover plumbed up properly to allow for the suction, it might not do much sucking and just take the easy path of getting all the air from the main intake on the cleaner body. If the diameters are different, I could always restrict the one I have a bit to make it the same.

If I go down the path of hooking the rocker cover to the carb, is there an adaptor of some sort to allow for the difference in size between the rocker cover and the carby point? The rocker cover is about 1/2" while the carby is about 1/4".

Cheers Rocky

Thanks eightfifty.

The filler cap is a non vented one and I've checked the tappet chest cover for a baffle and there is one. I used a zip tie and it pretty much stopped at about the length of the pipe on the cover.

The air cleaner inlet for the rocker cover hose is about 3/8" ID so maybe a small restriction would make it work better. In my reply to Dave (Steam) I asked about the main air intake diameter between the metal one I have and the standard one for an 850. I'm thinking that the one for the 1 1/2" SU might be bigger than the one for 1 1/4" SU as the bigger carb is designed for bigger engines and therefore needing more air.

I would appear that the chest cover design I have wasn't all that successful as was changed to ones with a rise up before dropping down in order to prevent any oil coming out of the cover to go out the pipe and would instead drain back into the motor. In hindsight, it would have been better to fit one of the later ones which I can still do if all else fails.

My plan at this stage is to get a good connection between the air cleaner and the rocker cover, check to see if I need to restrict either that connection or the main intake part of the air cleaner body to allow a bit more suction from the rocker cover and modify the current hose on the chest cover to include a drain part and a free to air part. Now I know that the purpose of the cover is to provide air to assist with breathing, then maybe as a result of putting a long length of rubber hose on the end of the chest cover pipe, I've made it too hard for any air to be sucked in and now the cover is effectively not doing it's intended job. The hose finishes below floor level and when driving would create a vacuum in the hose I reckon instead of allowing air to be sucked in.

Here's a sketch of what I'm thinking of doing. The open to air part of the T would be as close as possible to the end of the cover pipe and would allow for air to either be sucked in or blown out if the crankcase pressure is too high (act like a breather). I'm thinking that most of the oil in the discharge would run straight down the hose and collect in it, ready to be drained.

I possibly can't be any worse off than what I am now and hopefully catch at least some of the oil to reduce the mess it's making. If that doesn't work, I could fit a later model chest cover with a riser pipe on it which should keep the oil in the motor.

Cheers Rocky