Do flatheads need zinc in the oil?

4

4dy

Member
I have a 1937 85hp flathead. I was told old rod bearings need zinc in the oil for proper lubrication. Is this really needed? Do any modern oils contains zinc or do I need to use a zinc additive?
 
IMHO yes and yes there are current oils that contain zinc additives or you can just add the additive yourself (cam companies sell it). BUT, this is one of the topics that there are about as many views on the subject as there are people posting. Zinc helps with friction and is mostly needed with flat tappet camshafts. The relevance is related to valve spring pressure and flatheads use low spring pressure, so not as critical as later flat tappet engines.
 
KiWinUS said:
Does Shell Rotella still have zinc in it ?
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yes

as tested:
zinc: 1454 ppm
phos: 1062 ppm
ZDDP: 1200 ppm

Don't get too wrapped up in all the zinc and ZDDP talk. Modern oils with lower zinc levels are far superior to the engine oils of the flathead era no matter the zinc levels they may have once had.
 
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Seth, When was the test? We keep hearing that zinc has been reduced. My mechanic just put in Rotella 15W-40 and added ZDDP.

Seth Swoboda said:
yes

as tested:
zinc: 1454 ppm
phos: 1062 ppm
ZDDP: 1200 ppm

Don't get too wrapped up in all the zinc and ZDDP talk. Modern oils with lower zinc levels are far superior to the engine oils of the flathead era no matter the zinc levels they may have once had.
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Any name brand oil with a 40 weight or over in its designation has enough for most any flathead. Never use an oil the says "For gasoline Engines Only" as these are typically for roller, late model engines
 
There is enough zinc in modern oils for our flatheads. No need for any additives or high zinc oil. If it makes you feel better use it. I don't.
 
Penrite HPR oils also have zddp in them, but as others have said, it's not necessary for stock valve springs and stock cam. If you were to run high spring pressures and an aftermarket cam, which is quite possibly ground on a Chinese made billet, then it would become necessary. Until the advent of OHV V8s from Caddy, olds, Chrysler, there was no zddp in oil. The higher valve spring tension these engines ran destroyed their cams, so manufacturers urged the oil companies to add the zddp.
 
An oil thats designed to be used in a car with a cat converter contains very little additives that can be "plating" the converter so the old type of metal additives has been replaced.
Still the oil has to do the job its specified for...how they fix it is up to each companies research staff.
And the old formulas are often still available on special order sometimes designated "classic" just dont put it into your modern car !
 
Now i run Dynocat, 1340 ZPPM.
The engines turned real quiet right away compared to the Castrol we`ve always used. Castrol removed all the good stuff gradually, and mechanical sounds increased with it in all the old crap we have running.
Now i`m back to listening to the low hizz in the carb and the thin snoring sound from the flapper valves in the fuel pump.
 
I use Brad Penn for years in flat tappet cam engines-- the BEST oil I found yet for old engines-- it is made and engineered for those kind of engines
 
38 Conv said:
I use Brad Penn for years in flat tappet cam engines-- the BEST oil I found yet for old engines-- it is made and engineered for those kind of engines
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I second Brad Penn. The zinc issue has been covered about a million times on various forums over the last 5-10 years. The zinc issue seems to stem mostly from new camshafts having the lobes wiped during break-in. If you're just running a regular, well-worn old flathead, off the shelf oil is probably fine.
 
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Increased use of ZDDP in motor oil came along when warranty problems started to rear their ugly head in the more modern high compression overhead valve engines of the later 50s on up. It is still a requirement for those engines. More modern engines have rollers and overhead cams that don't require a high concentration of anti-wear additives. With the large size cam followers of the flathead, it is questionable whether it would be necessary even with a hot cam & stronger springs.

It certainly won't hurt a flathead and any oil is better than no oil but it isn't much of an issue one way or the other.
 
When concentrations approach 2000 ppm, it starts to become corrosive. More is not always better. ZDDP was introduced in the early 40's at a level of about 300 ppm. By the mid 50's, the concentration had increased to 800 ppm which is where we are at now.
 
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