I have several flat-tappet motors in bikes trucks and cars. After DELO dropped the zinc etc additive I started using an additive that cost about $12 at the FLAPS. Then I discovered valvoline racing oil with zinc so now I'm using that. It's a little more expensive but not $12 more per oil change.

1951 3800 1-ton
"Earning its keep from the get-go"
In the DITY Gallery
1962 261 (w/cam, Fenton headers, 2 carbs, MSD ign.), SM420 & Brown-Lipe 6231A 3spd aux. trans, stock axles & brakes. Owned since 1971.