VENT PIPE

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JohnBSpk
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VENT PIPE

Post by JohnBSpk »

I know there has been loads on this topic however may I ask of you guys how to configure my late 1963 1098cc Vent pipe. see pic so getting the right configuration and without it spewing oil (which at the moment is being caught in a temp container) out both over the skuttle and floor.
My problem is I have only just come back to run a Minor again these last few weeks and whilst the body's great I can at least sort a majority of mechanical bits out which Ive done. but the vent is now a real pain and as my memory of improvements when I last had one has gone, so its back to a learning curve again ref subtle sorting problems.
I believe I should have a non vented oil cap for this config, ? and believe that a canister type filter from the crankcase panel would be better and go back to the inlet manifold with a gauze/pcv ?? filter maybe ?? I don't know, !!! However the previous comments have not stated they had a servo unit which I,m thinking is connected to the right place e the manifold ?? It does have the vacum pipe from the inlet to help the servo so I,m stuffed as to the best set up here.
Your help would be very much appreciated and if possible where to source the bits I may need to re-jig the set up.
I just wish to stop the crankcase breather at the minute from both ejecting mis and oil and I believe balancing the c/case pressure to a better degree and just having the most practical set up.
thank you for reading John
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svenedin
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Re: VENT PIPE

Post by svenedin »

Good grief that is a lot of oil from the tappet chest draft tube. Definitely not normal at all.

For a 1963 the rocker cover with breather tube and pipe to the air cleaner is correct. I suspect your manifold with tapping for a brake servo hose is from a later car.

Regarding the oil filler cap being vented or not I believe that with your set-up it should be vented but some people have experimented and have found a non-vented works better.

I would suggest taking the rocker cover off and checking that the metal breather pipe is not blocked. The same with the hose to the air filter. It seems your crankcase breathing is not working at all. I would also check the large rubber gasket/o-ring between air filter housing and carburettor and carefully check the breather hose for cracks. Perhaps for some reason, no vacuum is being drawn. A failed o-ring or perished hose may account for this. There should be jubilee clips on the breather pipe at either end. If the pipe needs replacement make sure it is a reinforced hose suitable for oil/fuel. Lastly check the rocker cover gasket as if it is leaking the breather system will be ineffective.

If everything is satisfactory with the breather system and it still spews oil from the draft tube then I would proceed to check the compression in each cylinder of your engine. It is possible that there is excessive blow-by that no breathing system could cope with.

Moving to a later closed circuit breathing system is possible but would not be original for a 1963. If there is an engine problem it would not help much. There are various ways of doing it, some more expensive than others. For instance, the expensive way (and probably best) is to use the later HS2 carburettor which has a connection for a breather hose. Then a "chimney" type oil separator is fitted in place of your draft tube type and the chimney connected to the carburettor with a breather pipe. This avoids having to interfere with your brake servo. You could keep your breather rocker cover too by connecting a pipe via a V-piece to the breather pipe going to the carburettor. The cheaper way is to fit a second hand Smiths PCV valve to the inlet manifold instead of the brake servo. You would then buy a carburettor spacer plate that has a servo take off on it and move the servo pipe to that. Smiths PCV valves are not easy to find though......You also need a manifold that has the holes tapped for the PCV valve support bracket (I cannot see if you have that).

Stephen
Last edited by svenedin on Thu Mar 21, 2024 5:37 pm, edited 1 time in total.
1969 1098cc Convertible “Xavier” which I have owned since 1989.

Stephen
philthehill
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Re: VENT PIPE

Post by philthehill »

The manifold in the photo above is the early 2 piece manifold for a H2 SU carb. There is no provision for either a PCV valve or servo vacuum take off. The manifold appears to have been drilled and tapped for a vacuum pipe take off. Only the later manifolds have provision for the PCV valve and servo take off. Dependent on the manifold (part number distinct) there may be one or two bosses, the bosses can be drilled and tapped or just solid.
The later manifold with take off provision suit the HS2 SU carb. The carb needle needs to be changed if a PCV or breather into the carb body is utilised.
By all means check that there is no blockages in the breather pipe and the correct rocker cover filler cap is fitted. It should be a breathing type filler cap.
If all pipes are clear I suspect that you have worn bores or broken rings. A compression check should make for a clearer diagnoses.

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svenedin
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Re: VENT PIPE

Post by svenedin »

Hello Phill,

Although this is not relevant to the OP's issue you mention the need to change the SU HS2 needle when a PCV valve or breather into the carb body is used. I can find no reference to this. My car has run with a PCV from new and has only ever had an AN needle. Do you have a book that recommends a particular needle?

I have asked a contact who rebuilds SU carburettors for a living the same question.

Stephen
1969 1098cc Convertible “Xavier” which I have owned since 1989.

Stephen
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Bill_qaz
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Re: VENT PIPE

Post by Bill_qaz »

Are you sure your oil is not overfilled? Fill with correct quantity and then see dipstick reading to ensure you have correct dipstick and tube.
I have same set up as yours and have no clips on rocker cover to air cleaner hose and servo connection with no issues.
Regards Bill
philthehill
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Re: VENT PIPE

Post by philthehill »

I do have the SU Reference Catalogue. Burlen Fuels ALT9524, Issue 12/4, December 1998.
It states for a 1098cc 'A' Series engine fitted with a AUD 13 carb the needle should be AUD1478AN.
The catalogue does not give a listing for the HS2 carb when the PCV valve is fitted/used or for the HS2 carb with the breather pipe into the carb body.
As both PCV valve and breather pipe into the carb body will allow additional air into the manifold/carb the mixture will run weaker so the AN needle is not necessary the right needle for when a PCV valve or carb body breather pipe is utilised.
I will look for additional information and if necessary post any additional information found on here.
Here is a link to previous discussion regarding the correct needle when a PCV valve is fitted..
viewtopic.php?t=73786
My view regarding the correct needle for use with a PCV valve has changed somewhat from my 2021 view and the AN needle is as I stated above not necessarily the right needle - only mixture examination and road testing will confirm the needle required.
Phil

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svenedin
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Re: VENT PIPE

Post by svenedin »

philthehill wrote: Thu Mar 21, 2024 7:27 pm I do have the SU Reference Catalogue. Burlen Fuels ALT9524, Issue 12/4, December 1998.
It states for a 1098cc 'A' Series engine fitted with a AUD 13 carb the needle should be AUD1478AN.
The catalogue does not give a listing for the HS2 carb when the PCV valve is fitted/used or for the HS2 carb with the breather pipe into the carb body.
As both PCV valve and breather pipe into the carb body will allow additional air into the manifold/carb the mixture will run weaker so the AN needle is not necessary the right needle for when a PCV valve or carb body breather pipe is utilised.
I will look for additional information and if necessary post any additional information found on here.
Here is a link to previous discussion regarding the correct needle when a PCV valve is fitted..
viewtopic.php?t=73786
My view regarding the correct needle for use with a PCV valve has changed somewhat from my 2021 view and the AN needle is as I stated above not necessarily the right needle - only mixture examination and road testing will confirm the needle required.
Phil
Thank you. I don't think it does need a different needle from my own experience but I may well be incorrect.

Yes there is "air" being drawn in but that air is oxygen depleted because it is crankcase fumes and it also contains oil so it does contain fuel of sorts. My personal experience is that a PCV valve results in a mixture which is on the rich side.

Stephen
1969 1098cc Convertible “Xavier” which I have owned since 1989.

Stephen
JohnBSpk
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Re: VENT PIPE

Post by JohnBSpk »

Hi Guys
Many thanks for the tips and info I,ll start checking and also try the compression checks.
Again not sure what values I should expect from the compression checks in order to evaluate whether the rings/bores are too slack to get the crancase pressure sorted Again any values would be appreciated.
Many Thanks. John.
philthehill
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Re: VENT PIPE

Post by philthehill »

I would be looking for around 150 psi.

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svenedin
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Re: VENT PIPE

Post by svenedin »

As Phill says and also consistent compression across all 4 cylinders. If 3 are good and 1 is much lower you've found the problem.

Have a look at your spark plugs too and compare them against each other.

Also have you checked your valve clearances? Perhaps a valve is not closing properly.

Stephen
1969 1098cc Convertible “Xavier” which I have owned since 1989.

Stephen
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