Thank you gentlemen, much appreciated.
Steve, I will be sure to check that. It's interesting how engines can be so different, the Datsun LOVES timing. It idles at 17, with 34-36 all-in being plenty safe on RON 95 - so I made a silly assumption that 17 was also OK on the 6. I guess head design, compression, cams etc all play their parts. I replaced my 40+ year old one with an ATi Super Racing damper, having 360 degree timing marks - if it's acceptable in TR circles, I recommend it, it's a fantastic bit of kit.
Stuart, thank you for the recommendation. I just discovered t