Looks like I stumbled across the info I needed. Seems a 11mm bolt head won't swap with a 12mm bolt head cause of the head bolt holes. Go figure.
Any reason I can't swap a 81 1.6 head onto a 82 engine? The 81 uses head bolts that takes an allen and the 82 uses ones that take a 10 point male socket. Also what about headgaskets? I think the 81 uses a 2 notch and the 82 uses a 3 notch. Thanks in advance.
You can use them, but it may not be 100% bolt on and go. If the one has 11mm head bolts -socket head like you stated- it is 11mm, unless someone got cute and substituted boltls in there. The other will have a triple square which is actually 12pt and takes a special tool - is 12mm head bolts, UNLESS someone used gasser bolts in it and it is an 11mm block. Lots can happen in 30 years. If they are both the same then it bolts up. If you have a good 12mm head and need to go on an 11mm block it should bolt up as long as they are both 1.6 and mechanical valves. If you have a good 11mm head and need it to go onto a 12mm block you need to either machine the washer surface to accept a bigger washer OD, or grind each washer down to fit inside the head AND drill all the head bolt holes to accept the 12mm bolts. Then it should bolt on and run fine. This is true if both engines are mechanical valves, which the years you stated they will be as long as it is original.
I like 1.6l and 1.9l Diesels