I was having a problem starting my 960's 172ci gas engine. 12v conversion and it spins fast, I Was cranking it when suddenly it hydraulic locked up tight. Removed all plugs add water gushed out of all four cylinders when cranked. I have not been able to work on it lately, does anyone know what could cause this? The valves were ground a few months ago and I am concerned about the head.

Below freezing temperatures?

Anti-freeze?

Hard to understand how water could have filled all cylinders while cranking???

We just went through the 7th coldest winter on record here in E central FL but no freeze at our place. Any way this happened prior to the cold spell. I had been cranking it off and on for about 1/2 hr when it instantly locked up. I can't imagine how water could get in all four at once, two had a lot of water and two had enough to spray a good spray. I can't find anyone willing to repair it in this part of FL as gas engine mechanics as well as machine shops are a thing of the past.

Water in air cleaner?

Remove oil cup and inspect.

Had the cup off before and after, no water. I also thought the manifold could be a common denominator.

There are no coolant passages in the manifold although some of the manifold studs do extend into the engine water jacket.

Coolant in oil?

Obvious, but assuming that any vertical exhaust has been covered.