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So I finally got the m20b25 fired up which I must say runs lovely.

Unfortunately it has an oil leak. It’s coming from between the block and the head, central to the exhaust manifold.

Anyone have any ideas on this or am I looking at head gasket replacement?

Bad news, and also a funny place to start leaking. Not coming from the valve cover?

Hi Jeroen,

The valve cover is completely dry!

It’s been mentioned on Facebook that people have had leaks from the manifold studs and have rectified this by removing, cleaning threads and thread locking them??

Maybe I’ll look at this as I’ve had the studs out and replaced before the engine was fitted

I've had an M10 with studs in through holes which nearly set fire to my car. Let alone the leaks. You can see the through holes from the top when the rocker cover is removed.

I have now an M10 without these through holes, so no risk for hot oil on a hot exhaust manifold. Bear in mind that there are thread lockers and thread sealers. Locker is not what you would use on these studs, if it is a through hole. But make everything very very clean otherwise it doesn't help.

Ah quite likely is the exhaust manifold studs then!

Took the studs out and thread sealed them.
I’ve run it to temperature and so far no leaks!
As always thanks for the info

Pfew! Much better than having to remove the head again!