Is there any sort of rough/general chart for ZDDP ppm vs. spring pressure for older, flat tappet engines?

Joined
Nov 22, 2020
Messages
516
For my old Toyota pickup, with the 22RE 4 banger/shaker engine, it seems like a lot of guys are obsessed with the ZDDP content of the oil, and even go as far as to run diesel engine oil for higher ZDDP levels because they believe their cams are going to melt away without it. I think stock, these engines have a valve spring pressure of under 70 lbs. Our local auto shop is one of the best in the state, and the owner knows more about all makes and models than anyone I have ever met before. In his experience, these engines almost always die on the bottom end, and hardly ever anything serious with the top end. He used to race this exact engine and had plenty of additional experience destroying them, on top of just seeing what came through their shop.

Even if the cams are not made in the most robust fashion for hardening, etc... would an engine with 70 lbs of spring pressure and non-aggressive cams need any sort of ZDDP levels over 800 ppm? Is there any sort of rough chart that gives an idea of how spring pressure could correlate to needed ZDDP levels? Of course many factors would need different charts, but I could imagine some sort of baseline could be displayed, right?

I'm using Mobil 1 10-40 HM in it now, which has a ZDDP ppm of 900. Even with an engine that does not have great design in the cam hardness and toughness, would this level of ZDDP be more than adequate for my engine?
 
Joined
Aug 20, 2003
Messages
18,158
Location
NE,Ohio
Seems kinda low
maybe run some pert plus shampoo in your engine.. it has more zinc in it than that.

sarcasm aside.. that is plenty. Now if you have a hotrod with flat tappets and high spring pressures.. more is better.
 
Joined
Aug 25, 2018
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Location
South Carolina
The 22RE is an OHC inline 4 cylinder. It's perfectly fine on 600-800 ppm. Your engine doesn't have high spring pressure because there's not a high rocker ratio nor lots of lifter, pushrod, and valve weight to keep under control. OHV pushrod V8s deal with higher spring pressure, rocker ratio, and valvetrain weight that makes the additional ZDDP more desired. Even then, most OEM cams are mild enough to be fine on 600-800 ppm as well.
 
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