Morris Minor Owners Club

any ideas where it may be coming from/what to tighten?

Ben

Petrol I presume?

seems oily, and burning into a varnish on the intake manifold

seems oily, and burning into a varnish on the intake manifold

you are sure it comes out of the carb, not the manifold?

can oil leak out of manifold?

Only if it's porous! The older style carb can certainly leak although quite how it gets up onto the manifold I don't understand. The jet assembly is held in the base of the carb by various glands and washers - these will have hardened over the years. You really need an overhaul kit from Burlen - this will include all the parts , probably (hopefully) including an upgrade to viton rubber gland seals. I think it's burlen.co.uk - someone will know for sure! Or just google for it.

At the bottom of the float chamber you will feel the tube which feeds
the petrol from the bowl to the base of the jet. this is held by a small
nut at the bowl end. Try gently tightening it. If that doesn't cure it then
check that the petrol is not actually overflowing from the very top of the
float bowl due to a dodgy float valve/needle.

ben739 wrote:can oil leak out of manifold?

Only if it's getting in there in the first place!

No, even if somehow the manifold was being filled with oil, if the gaskets were good then no oil would leak out (they have to be air tight, and air is generally thinner than oil ;) ). Aside from which, if you've got substantial amounts of oil in either inlet or exhaust manifold, you've got far bigger problems than a slightly staining leak!

If you are indeed getting spillage onto the manifolds (either upper or lower surfaces) I would definately suspect the rocker gasket first.

However, if the spillage is onto the exhaust downpipe then it could well be a fuel, not oil, leak. Petrol being heated quickly and evaporating off a downpipe will often leave a stain, more noticeable on a clean (stainless or fairly new) pipe. I reckon Willie and bmc have nailed that one - It isn't going to be oil, but could easily be fuel from either a knackered jet flexi pipe, poor seal on said pipe into float, poor float etc (my guess would be the little O ring seal on the jet pipe to float chamber connection).

Thing is, if you're getting a leak that you can see, you should be able to smell it. Burning oil has a very different smell to burning petrol, which will at least help narrow down which it is. If you're not too worried about unhealthy smoke try dripping half a teaspoon or less of engine oil onto a hot manifold and take a miniscule whiff of it. I always find petrol has a very harsh scything aroma in comparison to oil when dripping onto an exhaust...

But if you can take pics of at least the after effects of the leak then please post them. Chances are someone who's had the same problem will be able to spot it straight away when they can see it