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[pd110961]

a head gasket swap shouldn't eat into your tinkering time.. I recon , if I had all the correct spanners / sockets out, I could do one in less than an hour!

[Dennis C]

If you are sure it is coming up along the stud you could always replace the standard washer with a Dowty washer as a temporary cure until you need to remove the head

[Tim NZ]

The stud beside the spark plug screws DOWN into the crankcase, not the barrel, and there is no direct source of pressurized oil near that stud.


For there to be oil on the barrel/head surface it has two sources: DOWN the head nuts, and under the head nut washers, or from the pushrod tunnels, which is on the other side of the barrel...


Over torquing the nut between the pushrod tubes in a forlorn attempt at stopping an oil leak there simply distorts the barrel, which will show itself as a shadow in the bore adjacent to the stud as and when the bore is parallel honed.


For there to be oil pooling around the spark plug, AND for it to be coming UP the LH head stud to get near the spark plug, it is first coming down the internal head nuts and passing around the barrel head joint.


OR there is a casting/machining defect in one to the drinkings for the head nuts? But obviously this 'oil leak' was not there previously so I discount that situation.
The only other External possibility is oil leaking from one or the other rocker covers?


When you eventually do get to take the head off, the gasket will be 'wet' with oil...

[Bullet Whisperer]

One more possible cause is the oil might be getting past the cylinder base gasket and being blown up that barrel stud, as the piston descends. Sometimes the face to face fit of the barrel / crankcase mouth is not perfect and the base gaskets are not always crushed as much on the inside diameter as on the outside. I have lifted cylinder barrels to see base gaskets which have been little more than a soggy black 'goo' around this stud. Even the very little crankcase pressure which can momentarily be created by a 'duckbill' breather pipe can be enough to send small amounts of oil up this stud. You can either put up with it, try a 'dowty', or other type of sealing washer, as suggested by Dennis C, or strip the top end to whatever degree necessary - and maybe down as far as the base gasket, if this turns out to be the problem. Cheers, Paul.

[bigpete]

Thanks to you all. Tim you are right about that cylinder stud it is a full length stud,I was sure it was just a short one, but after checking our hosts online parts list it all becomes clear. I can't believe I had it stripped down last winter and had not remembered that( I blame it in old age and poverty ).Curiosity will get the better of me and I will end up stripping it down .When reassembling I will take on board what Tim and Paul have advised .Cheers Pete

[ric]

Another source of a top end oil leak is via the rocker cover bolt holes. Easily detected with a cotton bud.

[jefrs]

bigpete - after rebuilding one engine I found I had a cam-follower left over. That caused a moment

[Tim NZ]

There is one other rather remote potential source of the oil around the spark plug, but you have not mentioned any excess smoke or 'wet-sumping'?


Depending on the year of the motor, the 350 does not have an oil seal on the timing side end of the crankshaft, (or with later motors if this seal is damaged or incorrectly installed) this often allows the oil in the timing chest to drain into the crankcase (wet sumping).
On start up the excess oil in the crankcase is forced past the rings and will manifests itself as Blue smoke and Oil being blown out the exhaust.


The excess oil will also be forced out past the plug and de-compressor threads...