The short bolt was in the engine when I pulled off the head?? Had a weird top on it too....

Got rid of it on the rebuild and used another head bolt from a 120Y which also had 13 stamped on the head.

Was all a bit weird - but I think every Datsun owner who hasn't owned their car from new has had a few of those moments the..."What the hell? How was this car able to drive around with this bolted there!"

Good luck Michael - give it a kick, just listen carefully. One extra thing you could do is spray to rockers at least with some assembly lube.

It's Molykote in a can - some sort of gray graphite like stuff - I've sprayed it all round when re-assembling.

It's purpose is to lubricate parts on first start before they are adequately coated in oil...don't know why I didn't think of it before.

It's the grey stuff on the crank below