Years ago I rebuilt my R-16 engine ... several times ... because it kept overheating. Once, I pulled the head after only a few hours running, and the gasket came off clean enough that I noticed some green coolant spots on the gasket, where there were holes in the head, but not corresponding holes in the Renault gasket, so it was choking flow and causing the overheating. Easy solution is to punch a few extra holes in the Renault gasket - you just have to know where.
I just pulled the head again (after 30 years in storage), and figured I would put out pictures documenting the difference.
Below is a picture of the head, as well as the comparison of the original gasket, versus my modifications.
Engine is really clean inside, but there are metal shavings in the oil pump and a heavy groove scored on one of the main bearings. I suspect there were chips in the oil galleys from the last rebuild that were not cleaned properly. No damage to the crank, so I'll have it align bored and put in new main bearings and I should be good to go. I hope.