The F355 is in for it’s annual service and this one will require an engine out and belt change amongst many other things. As you can see above, indeed the engine is now out.
Interestingly, there is some major corrosion present on the outside parts of the plugs as you can see above for cylinders 1 – 4
and cylinders 5 – 8, above. This is strange given that the corrosion is on the part of the plugs that is outside the cylinder! It is also interesting that two plugs on either side are largely unaffected while two others are quite corroded. The part that goes inside the cylinder is fine. This kind of suggests that somehow water has been trapped in and around the plugs for some reason.
Next was a leak down test on all the cylinders.
Most of cylinder are good, like above, except:
Cylinder 4 at 30% and
and Cylinder 3 also at 30%.
This is a loss of power in those cylinders and is typically caused by wear on the valve guides. Getting that fixed is a major job for the future but it good to have these readings as a benchmark.
No signs of issues with the evap system but got a replacement charcoal cannister just in case.
Still more work to be done but the corrosion on the spark plugs is a bit of a mystery and the valve guides will need replacing down the track as well.
Let’s wait and see what else is found.
Love the F355 
Water on the portions of the plugs above the threads is likely the paper gasket having failed on the ‘cinquevalvole’ cover. Any rain or wash water can easily go through the engine cover vents and these gaskets are usually ruined by the first spark plug change, and seldom replaced.
Otherwise, the plugs all look fine, and the corrosion was doing nothing to hinder their performance.
30% leakdown is not insignificant, and fixing it is an engine out ordeal. If you can somehow swing repairing this now, it would be best case scenario. A really leaky exhaust valve guide can burn up said valve rather quickly, leaving you with 100% leakdown, a very not fun car, and another engine-out.
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Yeah we kinda figured that the water was a gasket issue. Interesting that it has happened on both sides but towards the back. Replacement gaskets seems to be certainly called for.
Agreed, that the leak down test indicates that the valve guides need to be done. This is first leak down test I have done on the car since I have owned it now (over 10 years) so I suspect it has been around this level for a while. I however started the process of getting it resolved and unfortunately, it is not something that can be accomplished during this service. The challenge is apparently, to assemble all the required parts prior, which I have now initiated.
The main aim of this service, apart from the engine out, was to get the suspension done. Next, will be the valve guides.
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do you follow Restored_by_Elliott? He’s in Sydney and is the F355 guru like I’ve never seen. When I was visiting from the states he was kind enough to invite me to his shop. He does some incredible work. True perfectionist.
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Yes I know Elliot
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