Next oil leak

[Tom and Maria]

Thanks to everyone who replied to my recent sump seal post, all tight now (with cork, rubber ones on standby if needed).

Since the sump has stopped dripping a leak from the clutch housing dribble pin has got much worse. The faster I drive, the more I lose. about a pint every 150 miles when doing 50/60mph.

I am guessing that this is the scroll on the back of the crank being worn with age? But, could I be lucky and it be the gasket behind the rear plate?

Re crankcase pressure I should mention that the rocker breather goes to the carb manifold through a 2mm aperture. tappet chest breather is clear. All pistons push 145psi.

Do I:
Lift the engine out and change the rear plate gasket and see if it improves?

Hang on and buy a new crank plus associted parts? (shame as current crank is otherwise fine)

Increaser the breather aperture to 2.5mm/ 3mm

Thanks in advance,

Tom

[Jefftav]

Do the easy things first. Take off the breather hose from the rocker cover to the carb and check that it is clear including the rocker cover outlet (you may need to take off the rocker cover) and similarly at the carb end check that it is all clear and some new hose might be useful in case it has collapsed internally. 2mm does sound small but I don't know for sure if anything bigger will make a difference and a bigger hose won't do much harm if you wanted to try it?

Look on the bright side the oil leaks protect the underneath of your car from rust

[katy]

Re crankcase pressure I should mention that the rocker breather goes to the carb manifold through a 2mm aperture. tappet chest breather is clear. All pistons push 145psi.

If the engine is drawing in through the rocker breather, I would suggest that you plug off the tappet chest breather. That way the engine is running with a negative pressure internally.

[Tom and Maria]

The current setup is - in through the tappet chest cover and out through the rocker cover via the carb. I have a solid filler cap so these are the only two vents. I believe this is correct (?)

The hose is new and I cleaned the swan neck a few weeks ago so there shouldn't be the problem there.

I might try opening the hole in the carb manifold a tiny bit. I'm sure I remember seeing 1/8'' mentioned on here as an okay amount, maybe I will re-drill it to that amount and see what happens. I only recently put the hose there as previously it was going to the air filter, maybe I was too cautious when selecting the size?

Does anyone know of a trick to check the breathing? Should something happen if I cover one or both of the holes at idle?

[MarkyB]

If the hole in the carb manifold was there for a vacuum advance it will be too small, if it was there for a servo it will be too big.

[Tom and Maria]

It wasn't there for either, in fact it wasn't there at all until I drilled it there a few weeks ago.

I'll try opening it up a bit and see what happens. It is only in the carb spacer so if it messes things up I can replace it easily.

[bmcecosse]

I used 1/8" (3mm) to great effect -so double the area of your 2mm hole. How have you connected the breather pipe? I also left the other breather open to allow fresh air to be drawn through the engine. The check is - hot engine idling, remove the oil filler cap and rev up - is there a plume of smoke/fume? 145 psi is not particularly good - but not desperate either....... It won't be anything to do with the adapter plate gasket. It may be worn main bearings - flooding the rear scroll beyond that which it can reasonably be expected to retain........ Hows the oil pressure??

[Tom and Maria]

Okay, I've drill the hole out to 1/8''.

As you can imagine it completely leaned out the mixture, but turning the carb adjuster five flats seems to have sorted that. In fact I still think it might be a touch too lean, white plugs and running hotter than usual. Is it unreasonable to turn the nut that much?

The breather pipe goes from the rocker cover to the spacer bertween the carb and the manifold. I've turned a little bit of brass to mate the two.

If I rev with the engine hot and the rocker cap off it doesn't blow smoke or anything but you can feel a whaft of air.Can only compare it at idle to holding your hand in front of your face and saying pa pa pa in to it.

I'm afraid I'm yet to fit a proper oil pressure gauge so no idea about the pressure. the PSI readings were taken cold, I'm about to take some hot ones now...

[bmcecosse]

Obviously that hole will have a much greater effect at idle than during full bore running, so you will need to adjust and see what happens. It may need a different needle to get it right. Running too weak can dmage the pistons - so keep an eye on these plug colours. Light beige after a good run is good.