TheFlyfish

I have two 4.5 16V engines standing in the corner, the best one of them is going in my boat. One stands with the heads taken off. I removed them half a year ago and put the whole thing aside. There was some strange blue/white build up in the cooling chamber around one cylinder, which I didn't remove, when I stored the engine (yes, should have done that...) Yesterday me and a friend had a look at the engine and I saw that this build-up had creeped onto the top of the cylinder and also onto the piston. When I removed it, I saw that there was some corrosion on the cylinder, marked in the red circle.

What to do about that ?

Is there a hi temp liquid gasket I could/should apply in that spot or do I need to have the surface machined?

GlenL

First, measure it to see if it's just a cosmetic blemish or a pit. If it's a pit then you'll have to remove all the head studs and have the block machined.

High-temp metal fill will work for a while but, eventually, it will burn through and you'll be fixing it later.

TheFlyfish

It's not clear on the picture, but unfortunately, there is some pitting, haven't measured how deep, but quite shallow. If it was around a water passage, I would not be afraid to clean it well and use some good liquid gasket. But here, I'm a bit more concerned. Machining the block would probably be the best.