Engine breathers

[andrew.searston]

I have a 1967 minor with a 1098 engine it has 2 breathers one on rocker cover and one on side of block. Could i do away with the rocker cover as i have another cover without the breather. Its currently going to nothing as it came with a bigger carb on it. Would it build up to much crank pressure?
Andy

[philthehill]

Is the breather on the cam follower cover connected to the carb/manifold via either a emission control valve or direct into the carb?

[andrew.searston]

Its just a little pipe from the chest cover pointing to the ground nothing to the carbs. So i get oil fumes in car but doesnt leak out

[philthehill]

Andrew thank you for the quick reply.
Personally I would stick with the rocker cover breather and if necessary route a rubber pipe from the rocker cover to meet the existing pipe so that they both exit the engine bay together.
You could extend the existing breather pipe to exit well below the engine.
Of course it would be better all round if you had the front cover with canister which connects with the emission control valve on the inlet manifold.
I take it that you have no air cleaner to rocker cover breather connection that you could connect the rocker cover breather pipe to?

[Declan_Burns]

Andrew,
If you do as Phil suggests I would be inclined to add a flame trap if you don't have the cover with the canister which has the flame trap in-built.
Here's a drawing for better explanation. The t-piece and U-tube I used is just to take measurements.
Here's a good article on how this set-up actually works
http://mgaguru.com/mgtech/engine/cv103.htm



Regards
Declan

[andrew.searston]

There is know where to Connect it to. If i was swap the rocker cover for the alloy one i have and have just the one breather on the side of the block would there be to much crank case pressure?

[Declan_Burns]

Andrew,
You will of course need the vented oil filler cap and connect the PCV set-up direct to the side cover pipe. Then you have in effect the closed circuit breathing system as on 1275 engines. Measure it as it is right now and then after you change over and you will soon see.
I did a lot of experimenting with this system on my MG TD and it had a dramatic effect on the oil leak from the non-existent scroll seal. By inducing negative crank case pressure, infiltration air is drawn in via the scroll on the crank. When air flows in, oil does not want to flow out.

Regards
Declan

[IslipMinor]

Can you post a picture of the top and carburettor side of the engine? In particular, what carburettor is fitted?

The early 1098 engines used a very inefficient crankcase breathing system that drew air from the air cleaner through the rocker cover into the crankcase, and out through a 'draught' tube attached to the front tappet cover. The system only works at best when the car is moving, and often results in oily fumes contaminating the air filter element. The oil filler cap is 'non-vented', i.e. sealed, as the inlet to the system is from the air cleaner.

The later 1098 engines used a 'closed circuit' system with an oil separator on the front tappet cover, and a tube up to a positive crankcase ventilation or 'PCV' valve on the inlet manifold. For these engines the oil filler cap is 'vented' and filtered, as it is the inlet to the system. This is much the same principle as all modern car engines today.

If you have the earlier 'draught' tube from the tappet cover, then you need a filtered inlet to the rocker cover. Sealing it up will create pressure and very likely oil leaks (even more than usual!).

I wonder if, on the earlier engines, a combination of sealed rocker cover and vented oil filler cap would work(ish)? Instead of the connection to the air cleaner? The test would be if the outside of the rocker cover remains completely oil free, it is working!

If you have an HIF carburettor as your 'bigger' carb, they are usually fitted with a crankcase breather port, which could be connected directly to the tappet cover oil separator (not the draft tube), in conjunction with a vented filler cap.

[andrew.searston]

Hi guys
So here is a picture of what ive got. Only just bought the car so have done nothing to it yet. If someone could add a picture of best way to sort the breathers out that would be great

[Declan_Burns]

Andrew,
The second half of the pipe coming from the tappet chest is missing on your car. In other words you are missing the stack on the draught pipe. It should extend down past the bottom of the sump-difficult to see in this photo.
Regards
Declan

[firedrake1942]

That is an odd looking inlet manifold! What is the carb ?

[andrew.searston]

ah okay so ill try and find a extension to the chest breather. thats a good question firedrake, i was told its off a metro. the cylinder head doesnt look like a 1098 to me but might be wrong?

[philthehill]

When you remove the rocker cover you can see what the casting number the head carries.
The alloy rocker cover can have a breather pipe attached - most alloy rocker covers have a blank boss just in front of the oil filler cap.
Drill and tap the rocker cover boss and fit a union.
Here is a rocker cover with a prominent breather boss.

http://www.ebay.co.uk/itm/classic-mini- ... SwONBZBwSw

And here is a rocker cover with breather attached:-

http://www.ebay.co.uk/itm/Classic-Mini- ... OSwcgNZAbv~

[andrew.searston]

thanks been a great help. does anyone happen to have a block breather extension for sale?

[philthehill]

Andrew
As an interim - just slip a suitable length of heater pipe (exiting just below the sump) over the pipe and secure with a Jubilee clip.

[firedrake1942]

This is what it should look like in situ and there is one on eBay http://www.ebay.co.uk/itm/Morris-Minor- ... SwhlZYvJi-

[IslipMinor]

At the moment you have the worst of all worlds, an unfiltered entry to the rocker cover and crankcase that all sorts of muck and rubbish can get into, but the carburettor looks like an HIF, and the head, from the orientation of the thermostat housing and the heater take-off, is very likely a 12G940 from a 1275 engine - as already suggested remove the rocker cover and see what the head casting number is.

The original 'draught' tube actually has some science to it, it is NOT just a simple tube exiting somewhere near the bottom of the sump.

If the HIF has a crankcase ventilation port, which most have, then there is a simple, good solution available:

Replace the front tappet cover with one from a later 1098 engine with the oil separator, and connect the outlet tube from it to the port on the carburettor AND fit a vented oil filler cap. Either replace the rocker cover with a non-vented one, or block the existing take-off, and you will now have a proper closed circuit crankcase ventilation system!

Can you post a picture of the rear side of the carburettor? It should have 2 ports, the larger one is for the crankcase ventilation and the smaller one is the internal carburettor ventilation/pressure balancing.

You look to have a good intake system and a good head, the 12G940, but I wonder what cam has been fitted? The next upgrade should be a better exhaust system.

[andrew.searston]

So here is a pic of the carb on it

[dalebrignall]

ive got a similar set up , you do need the maniflow exhaust system and manifold to get the most of what you have ivv got a 1098, 1275 head hif 44 carb maniflow exhaust and manifold on standard cam its not a racer but lots of mid range tourque for overtaking lorries and it sounds lovley

[IslipMinor]

Andrew,

The carb looks like it has 2 auxiliary ports on it:

Turbo HIF Connections.jpg (31.91 KiB) Viewed 3569 times

The standard HIF has 3 ports:

SU HIF Connections.jpg (68.08 KiB) Viewed 3569 times

The 2 additional ports should be blanked off. I have seen comments that they can be connected together, but not from an authoritative source!

The remaining 3 are:
7 - Fuel inlet
8 - Vent tube - connect a length of small diameter hose to this. DO NOT BLOCK THIS OFF!
11 - Crankcase ventilation. Connect directly to the oil separator on the tappet chest cover - NOT the draught tube.

Finally fit a vented oil filler cap, and all good to go.