Around 1200ppm (.12%) is recommended.  To determine how much additive you will need will require that you know the content in the oil you start with and the content of the additive and then require some math in order to come up with the right amount.  Much easier and sometimes cheaper, to buy oil that is ready right out of the bottle.

I'm aware that my signature photo and many others are not working because of photobucket.  I just haven't taken the time to fix it.


Lawrenceville, GA

While I'm not espousing anything, back in the 80's a brand name oil, Pennzoil 10-40, had only 716 ppm of zinc  50's oils probably had less.


54 Victoria 312;  48 Ford Conv 302, 56 Bird 312
Forever Ford
Midland Park, NJ

The old engine oil debate...

"What was discovered through oil testing by several engine component manufacturers is that many older engines experience a short period of time during engine start-up where critical lubrication is insufficient between metal-to-metal lubrication points when using modern oils with reduced amounts of ZDDP/ZDTP. These same enhancers unfortunately have their downside: The phosphorus in this compound creates carbon buildup in engine bores and valvetrains..."

SOURCE- https://www.hemmings.com/blog/2012/10/18/tech-101-zinc-in-oil-and-its-effects-on-older-engines/

IMO- A pre-oiler is more important unless a very high spring pressure is used, especially if the engine has extended shut-down periods..

____________________________

The oil dilemma is as good as the discussion about assembly lube vs grease!!   We know that too much zinc is also a bad thing too.   What about the additives that are zinc replacement but don't contain zinc?   Isn't it true that if your oils too slippery that the lifters won't spin and that can cause wear on the cam?

As usual this subject brings up a 100 opinions on what oil to use.. However, we need to keep in mind that Y-blocks do not have factory roller valve trains like most modern cars. So, oils currently sold for late model cars with the "pinwheel gear" on the container, are mandated to have lower anti scuff additives, apparently for environmental reasons. Their anti-scuff additives may be marginal for our engines & are likely best avoided. Also, many of them are very low viscosity & not intended for older design engines.. It seems that 10-40 or 15-40 regular car oils are likely the best choice for Y-blocks..    


Paul

You guys that run heavy oil may want to keep an eye on the oil pump drive spline, if it gets worn and strips (and it will) bad things will happen.  

Wouldn’t that same ‘slipperyness’ apply to the lifter shaft/bore friction?

6 VOLTS/POS. GRD. NW INDIANA

Cliff, After 20 years and 50,000 miles when can I expect a problem with heavy oil ? 
Dan, There is no such thing as too slippery when it comes to oil.

An easy run engine may never show a problem, however if it sees a lot of RPM with the oil cold it will, all you have to do is take apart the engine and look at the oil pump drive, I have a 292 here now that threw a rod on the freeway with no warning, I will take it apart soon however I know the problem was sudden lost of oil pressure.

Apparently any day now.

Durham Missouri