Crankcase ventilation.

[tysonn]

Still plodding through this unfinished restoration,so many things done wrongly,bits missing etc etc I won't be buying another.Anyway the rebuilt 1275 midget engine is running albeit a bit roughly but thats maybe just settings etc.At present its just got a standard 1098 carb and inlet manifold.I have a HIF30,heated alloy inlet manifold and an early mini exhaust manifold to stick on later.The rocker cover is an alloy thing with no vent pipe and the cap looks sealed also.I have fit a rubber pipe from the canister thingy near the timing cover to the carb.There seems to be a fair bit of oil leakage after maybe 10 minutes running mainly from the area at the front right corner of the engine(looking from the front of the car)dripping onto the manifold,and down the back edge of the sump.These could be simply a matter of the PO not nipping everything up but I just wondered if the ventilation arrangement it has at the moment could be causing excess crankcase pressure?

[bmcecosse]

Indeed it will - get a proper rocker cover with a vent pipe and connect it to the carb. The leak sounds like rocker cover gasket anyway....... You will need the larger carb (hopefully HIF38) to get even 50/55 bhp from that engine.

[tysonn]

No the oils not coming from the rocker cover its lower down than that.The carb I have to fit is the 11/2".I'll try the rocker cover off the traveller to see what happens.

[IslipMinor]

When you say the tube goes from the timing cover to the carb - is that directly to the vent port on the carb or to the air filter?

The 1275 in-line engine is designed to run with a closed crankcase ventilation system, which creates a partial vacuum, and were never fitted with a vent connection on the rocker cover. The tube from the timing cover is connected directly to the ventilation port on the carburettor, together with a vented rocker cover cap, which is where the ventilation enters from. What 1.5" carburettor are you going to fit? From what you say it is an HIF 38? If so this will have the required port for the vent hose.

With the standard 1098 inlet manifold, does it have the PCV in the inlet manifold? If it does, for the time-being you could retain the alloy rocker cover and connect the tube from the timing cover to PCV AND fit a vented rocker cover cap.

If you fit a carburettor without a vent port, you will need to leave the connection on the timing cover open and fit a tube to exhaust the oily fumes down below the engine and use a non-vented rocker cover cap, but expect some oil leakage from the rear crankshaft scroll if the engine is worked hard. This is the old open system that was replaced with the closed system on later 1098 and all in-line 1275 engines.

Do not use a combination of carburettor port and rocker cover port, there is no oil separator in the rocker cover and it can ingest its own oil very easily! That is why the connection comes from the timing cover - the cylinder 'thingy' is the oil separator, and originally also had a mesh filter in it as well, which has probably disappeared over time!

[bmcecosse]

Hmmm - we always disagree on this one! My engine breathing is from the rocker cover to the port on the HIF38 carb - and it 'ingests' no oil whatsoever. Hard to imagine where your oil leak is coming from - if it's lower than the rocker cover joint. Is it seeping out the front of the joint between head and block??

[tysonn]

Thanks both for suggestions.The pipe from the "oil seperator"goes to the air cleaner.The rocker cover has the vented cap.I shall follow your instructions and pull the pipe from the air cleaner and let it hang for now.Yes carb is an HIF38 plus water heated inlet manifold.While youre on Islip fron what I have been reading about my clutch it looks as if there is a thicker release bearing available which may have given more push on the diaphragm.I have probably got the Minor one thats thinner?Just a thought.
Roy the oils coming from where you said plus from the rear of the engine and running down the sump.Mind you it was only running for maybe 10 minutes would this have been long enough to generate enough pressure to blow it out?
Give me bodywork anytime!!!!!

[bmcecosse]

Oh dear - can only assume the head gasket is leaking oil .......

[tysonn]

No bother.If the rest of the cars anything to go by hes probably not tightened the head bolts.Working through it bit by bit.

[IslipMinor]

The oil from the rear is likely to be from the crankshaft scroll that acts as the rear cranksahft oil seal. To work really well it needs the partial vacuum created by the closed circuit ventilation system.

Is there a port on your HIF 38 for the vent tube to be connected to? If so that is the best solution, rather than the air cleaner, which provides virtually no 'suck' at all.

[mike.perry]

It is no good venting the breather pipe to fresh air, the fumes need to be sucked out to maintain a negative crankcase pressure

[IslipMinor]

Agreed, but if the carb has no vent port or there is no PCV fitted, i.e. the earlier A-Series engines, there is not much choice really? That's exactly what BMC did pre the PCV and then the port on the later HS and HIF carbs.

[bmcecosse]

Well -they did their best by connecting the rocker cover pipe to the air cleaner... 'some' suck - but not a lot.....

[tysonn]

Pic of carb[frame][/frame]

[bmcecosse]

Excellent - that big one is the 'sucker' !

[tysonn]

Actually I may be the sucker!Thanks.

[brucek]

Most use the HIF 44 rather than the HIF 38 with the 1275 engine - certainly the 1300 Metro and MG Metro did. Might be worth a try

[tysonn]

Removed the inlet part of the mini manifold and got it on with the alloy inlet today.Bit of alteration with the choke and throttle cables etc.Does anyone know the thread size of the hole on top of the inlet which appears to be for a servo vacuum take off?I need to block it off.Been looking for an article that shows what all the connectors on the carb are for but cant seem to find it now?

[tysonn]

Just found the connections thread.

[bmcecosse]

5/8" UNF I believe

[tysonn]

OK carb connected up.Have had to improvise a plug for the inlet servo connection for now.I followed this pic which states that 1 & 6 should be joined,2 vacuum advance(my dizzy doesnt have one so I've blocked it off),3 to crankcase breather,5 fuel in and 4 is breather.Is 4 the breather for the rocker cover?I dont have one so can I leave this open or does it need blocking off?Reason I ask is that it wont run?Pump is filling the chamber and stopping,piston is free etc(carb is reconditioned)but the plugs are dry.[frame][/frame]