French rebuild

[brit plumber]

I’ve bought a French refurb engine and decided to give it a check over to be sure it’s not deteriorated since the 60s.

Externally it has some minor surface rust and has a damaged distributor cap but I thought I should take the head off to check the bores are good and there’s no foreign objects that have appeared over the last 60 years.

It looked good, a bit dirty where I guess it has a post build test run, but the cylinder walls are shiny and no marks anywhere, but then I noticed I could see the top piston ring between the piston crown and the wall. I’ve never seen this before and feel it’s far too much to be clearance. The pistons are plus 30 and I’m wondering if it’s got the wrong size fitted, even though it’s obvious run. I’ll attach a photo so you can see for yourselves (red arrow pointing to gap in ring). Is this normal?

[8683jb]

It's a pretty grainy picture but I wouldn't expect to see that much of the ring. How much clearance would you guess you have between the piston and cylinder?

[brit plumber]

It’s a large enough gap that my attention was immediately drawn to it and the ring.
I’ll attach the original photo. If I had to guess (I will try and get some feeler gauges on it) I would say it’s at least 40 thou.