Winter maintenance

[Ianfs]

There you go, I found one, now you can start.

A round tuit.jpg (19.15 KiB) Viewed 13161 times

[shibbs]

if only that would do it.

[shibbs]

I made a start on the head removal this week ( Tues) and it suddenly dawned on me that removing a head on the engine requires pretty much stripping down the whole top end of the engine (far more involved than my last).
Anyway, cracked on, and about 3 hours later the STBD head is now removed. Back towards the tail end of the summer some of you may remember i had a snag with a misfire, well whilst trouble shooting this i noticed that compression on No 3 was considerably low - 80 compared to the 185 of the rest. After doing a liquid compression test to rule out the rings i decided that i probably had a burnt valve..
Here i am. Unfortunately, i made a discovery that brought a bit of a sick feeling to the stomach when i removed one of the rocker covers..

Clearly a build up of moisture.

I found this strange as i serviced it inc full oil change when i winterised it and found no evidence of moisture in the oil then. I have taken a sample of the oil in the sump today and that is clear too. I am assuming that it may be caused by condensation from when it was run up after service to flush anti freeze through the system. I was aware of the hazard of condensation forming at this stage but thought i had allowed the engine to get more than hot enough.
Anyone think of any other reasons?
Having now taken the head off, the gasket seemed to be fully intact so am fairly confident that its not that.
Plan now is to do a leak test on the rings once again and also check each valve for its seal and go from there. As i said, i'm hoping to see a leaking exhaust valve on No3 but we shall see.. On the plus side, the manifold and elbow are good as new!
Anyway, started pretty much here..

now here..

Anyone had a similar experience?

[_Ed_]

Fair play! That oil in the water is really quite emulsified. Quite strange/interesting.

[shibbs]

Did a leak test today, cyl one leaking a very slight amount, cyl 3 passed the parafin within about 5 seconds and 5 and 7 were both fine.

2 new valves it is and a couple of hours grinding them in.

[shibbs]

And here is the cause,

and how it should look..

New seat i think.

[Ianfs]

How are you going to re-seat it, do you send the head away, or get it welded? It looks quite deep to grind in a new valve.

[shibbs]

I'll have to take the head to a machine workshop and get a new valve seat fitted. Will more than likely replace the valve as well and reseat them together.

[Ianfs]

I've been trying to work out how the oil has emulsified in the rocker cover. Clearly the valve leaked and must have therefore fed hot gases back up the stem, it is the inlet valve right?

The cycle would suck in fuel/air mixture, ignite and then exit via the exhaust port. The bad seal must send some of the hot gases back up the Inlet stem, but the gases clearest route would be back to the Inlet Manifold. So how would moisture be generated in the rocker cover.

Indeed, these are the parts of engine mechanics I am undoubtedly weak in.

[shibbs]

No it is in fact the exhaust valve, so my thinking is, where the raw water passes directly through the head above the exhaust valve I think moisture is being forced up the valve stem and into the rocker.
That is the only explanation I have managed to come to.
There was also a knackered seal at the top too..
Certainly isn't pointing towards anything else in an obvious way..