zinc or no zinc

35 rancho

35 rancho

Member
Have a fresh 1940 flathead. I fill the motor with pennsoil 10/40. my concerns aer the zinc additive??? I found Hy-per Lube at the local pep boys. Anyone tried it or any recomdations will help thanks dave
 
I wouldnt worry too much about it in a Flathead,I doubt there was a big concern over zinc in 1940 motor oils. I have been using Valvoline 10/40 in mine for years.Flatheads dont have a lot of spring pressure like overhead valve engines.
 
Stock flattie = no.
Flattie with aftermarket cam = yes.
Most aftermarket cams are ground on chinese billets which are not of high quality, and have lower Rockwell rating than stock Henry steel.
 
This is a topic that probably doesn't have a "correct" answer. The oils of the 40s and 50s had little or no zinc in them. As others have said, if you are running a hot cam with higher spring tension, a little zinc isn't a bad thing. Most of my friends are running Shell Rotella which is a diesel oil with zinc. I use Chevron Delo which is a similar oil. I use it, instead of Rotella because my local NAPA has it and because it comes in quarts and gallons. I am not high on zinc additives as I am concerned that they will collect in the bottom of the oil pan.
 
Before buying an oil additive with zinc in it I'd check out ZDDPlus. That's what I use. Their web site explains how it is not an "additive" like STP but a "replacement" of what used to be in oil for flatheads that's all but gone now. http://www.zddplus.com/
 
35 rancho said:
Have a fresh 1940 flathead. I fill the motor with pennsoil 10/40. my concerns aer the zinc additive??? I found Hy-per Lube at the local pep boys. Anyone tried it or any recomdations will help thanks dave
Click to expand...
Considering that you have a fresh flathead and you found Hy-per lube, by all means, use it. It is supposed to be equal to and better than zinc. It can't hurt and will give you peace of mind. :)
 
I've went to several oil siminars at motorhome rallys where they all said 10-40 isn't good oil.The only oil that may or maynot have the zinc additive is 15-40 which I use in my motorhome and all of my old cars.FWIW
 
The API rating of SM still has the zincdialkyldithiophosphate additive, it just dropped back on content from the older SJ rating. On a break in run its not a bad idea to run a straight grade non-detergent oil since the engine is starting out making metal to bed in rings, cams, and such. The cam should be coated liberally with a break in lube anyway. The detergent or dispersant oils hold these micro particles of metal in suspension and we all know how good the filtration system is on a stock Ford L-head motor. I will be running a straight SAE 30 non-detergent for the first couple of hunded miles on my 51 Mercury breakin run but I may add some tricresylphosphate (TCP) additive after the first 50 miles or so. After that SAE 30 with at least an SM rating would be fine. I don't see anything wrong with running SAE 10W40 with at least an SM API rating after the parts are all bedded in. The older API SJ is still available in Shell Rotella and a few other diesel engine type oils as was previously mentioned but that may not last. I still find some older Castrol API SJ oils in the NAPA stores. I guess folks buy their oil at other stores due to the price but I'll take what I can get as long as it lasts. After that it will be Lubriplate specialty oils, since they may be one of the only blenders of early API SJ rated motor oils left. You can use detergent oil for break in but I'd recommend a very early change of oil maybe first 75 to 100 miles or so and a filter change as well. Might not be a bad idea to stick with that for the first 200 miles or so.

With ZDDP additives you have to be careful not to add more than you need. Above 1200 PPM it actually starts to be detrimental to the lubrication capability. The 1200 ppm figure was in API ratings of SJ and earlier back as ar as 1988 anyway. The new SM rating still has near 800 ppm if I remember correctly. That is only a 400 ppm difference.

The type of oil you use has always depended on the temperatures of the operating environment and how much power you require in operation. For a big truck or a motor home, you will need heavy duty protection. In winter time up north you will need a low viscosity for starting and warm up. You just have to adjust to your operating environment.

Kerby
 
Last edited:
Why not use a quality breakin oil like Brad Penn 30W breakin, also Joe Gibbs has a breakin that works great also. there is no reason to take a chance.
 
35,
Some of the other guys hit on the most crucial item; valve spring pressure. For a stock engine you probably don't need to worry about it except at break in. I broke in mine with Castrol 30W and some ZDDP and after 500 miles I switched to Mobil1 15W/50 because it's intended for older engines and higher valve spring pressures. Check it out at www.mobiloil.com They have a description of what each oil is intended for and the charts that show how much zinc is in each different weight. I've been running it this way for a couple of years now without a problem of any kind.

Rich
 
Last edited:
A Ford L-head with an overhead valve conversion puts you back into the realm of the muscle cars of the 60s. Neat set ups but different valve spring preasures than a stock flat head. Lots of cam lube and heavy duty racing oil for start up.
 
The level of ZDDP needed is directly proportional to the valve spring pressure. Here is a reference to the definitive article on this subject: "In a SAE paper titled "How Much ZDP is Enough?" from 2004, the resulting trend of decreasing phosphorus is as a direct result of observations that modern engines, with lower spring pressures and lighter valvetrain, including multiple intake and exhaust valves, seems to require only .03% Ph to prevent wear. It was further documented that by increasing to 180 lbs of spring pressure with a .03% ZDP resulted in 267 mil of wear where with .05% ZDP concentration tests resulted in 26 mil of wear. That same .05% oil with just 205 lbs of pressure resulted in 153 mil of wear, requiring .095% ZDP to reduce wear, resulting in just 16 mil. The ZDP requirements of a motor oil are directly proportional to valvetrain spring pressure."

I don't have personal experience with stock flathead valve spring pressures but my researce indicated that such pressures were in the neighborhood of 70-120 lbs of pressure. If that is correct, then, according to the above article, at that pressure, something between .03% and .05% concentration of ZDDP would be adequate to substantially reduce wear. Inasmuch as most modern API-SM rated oils have that concentration, it does not appear that any added ZDDP supplementation is necessary, at least with fresh oil. However, studies have also showed that ZDDP concentrations up to .20% do not have negative impact on wear rates. So, ZDDPlus, which I use, that adds 1200 ppm to API-SM's 600 ppm totalling 1800 ppm is not detrimental, but apparently not necessary, at least not when the oil is new. What I could not find is the rate that the ZDDP depletes over time (because it is actually used up on the wear surfaces) and whether it might get too low before the next oil change if the oil alone just barely had enough to start with.

Even though it doesn't look like I need to supplement current oils with ZDDP at the oil change, just to be sure that there will still be enough ZDDP left by the next oil change I will probably go ahead and keep adding ZDDP, but in smaller amounts, just to be sure.

I've learned much today studying this out and feel that I have reached the correct conclusion on this matter. It is different than what I thought before.

Caveat: This conclusion is for ongoing, long term oil use with stock setups - not break in use nor higher than stock valve spring pressures which require much higher levels of ZDDP. That's another subject for another day.
 
Last edited:
You must log in or register to reply here.
Back
Top