Flat Tappets: Observed Failures

[BrocLuno]

There are a bunch ow AW compounds that can be put in oil ZZDP was cheap and easy, so it got put in older oils. Modern oils have to be backward compatible and they can't have higher Zn & Ph levels, so they go to the more expensive AW compounds.

Chevron is advertising 50% less wear from the new CK4 HDEO's and they would not make those big public proclamations if they did not have lab results and over the road test results to back it up. To many big fleet operators with lawyers would be looking to skin their behinds if it were not at least partially true ...

I would not worry terribly about modern oils. I do worry about viscosity and some about oxidation. But wear, no.

Biggest flat tappet I have built is a .630 lift BBC with more than 400# over the nose. Crane cam, Howards lifters, Howards springs, thrift store push rods, Comp stainless roller rockers in 781 heads. Peaked at 6,300 and revved to 6,500 for shift purposes. Ran two years on the street on Delo 400 before it got sold. No issues.

What are we trying to find out here ...

 

[supton]

Originally Posted By: BrocLuno
Biggest flat tappet I have built is a .630 lift BBC with more than 400# over the nose. Crane cam, Howards lifters, Howards springs, thrift store push rods, Comp stainless roller rockers in 781 heads. Peaked at 6,300 and revved to 6,500 for shift purposes. Ran two years on the street on Delo 400 before it got sold. No issues.

What are we trying to find out here ...


what that beast sounded like as it ran through the gears...

 

[turtlevette]

The 40w redline I put in my vette had a gear oil type sulphur smell so I suspect it has some ep additives similar to gear oil. The royal purple has an ep additive.

What's the down side of having these additives in motor oil?

 

[BrocLuno]

Hard on yellow metals IF you have a bronze gear in there anywhere ... If not, no downside

 

[Building3]

I thought that with over 200,000 posts on engine oil this would be a good place to post the question and ask for any experiences of a flat tappet engine failing after use of a modern SN/SM low zddp engine oil. There seems to be a lot of enthusiasm for oil here so if anyone did have a failure someone here might have had one. So far I have read that GM and some aftermarket suppliers have made poor quality cams/tappets that have failed. At least Pennzoil says that their oil is just fine in these engines. So I guess there should be no worries about SN/SM oils in a stock muscle car or classic car. If the engine has been rebuilt with substandard parts, then it will probably fail no matter what oil is used.

 

[SilverFusion2010]

There are a few situations where you need a high zinc oil and it’s always a high lift cam with lots of spring pressure. Your oem configurations were not that aggressive, and do fine with SN oils. Also consider that while zddp is limited to 800ppm, stuff like moly and titanium don’t have any such restriction and serve as anti-wear additives. They are more expensive than zddp, so they were less used until SN dropped zddp limits.

 

[Gokhan]

In classic cars I would use an oil with a high x in xW-y, such as 10W-, 15W-, or 20W-, meaning a thick base oil, and a high moly and ZDDP content. This assures best wear protection in classic cars where valvetrain stresses can be unforgiving. Conventional vs. synthetic is probably secondary.

A very good oil for classic cars is Mobil 1 15W-50 -- thick base oil and 1200 ppm phosphorous -- if your car is garaged in severe cold. Mobil 1 oil guide (link) specifically lists it for flat tappets.

You can also use a 10W-40 or 20W-50. 10W-30 is probably fine too but don't use 5W-30, as the base oil is too thin for flat tappets.

 

[Ducked]

Originally Posted By: Gokhan
In classic cars I would use an oil with a high x in xW-y, such as 10W-, 15W-, or 20W-, meaning a thick base oil, and a high moly and ZDDP content. This assures best wear protection in classic cars where valvetrain stresses can be unforgiving. Conventional vs. synthetic is probably secondary.

A very good oil for classic cars is Mobil 1 15W-50 -- thick base oil and 1200 ppm phosphorous -- if your car is garaged in severe cold. Mobil 1 oil guide (link) specifically lists it for flat tappets.

You can also use a 10W-40 or 20W-50. 10W-30 is probably fine too but don't use 5W-30, as the base oil is too thin for flat tappets.


Part of my retrospective rationalisation for mixing SAE 40 and 15W40.

 

[Building3]

Thanks for your thoughtful replies. My couple of classic/muscle cars are all factory spec whether stock or rebuilt so I can rule out the high lift/high pressure situation. They are all "broken-in" so I am not worried new engine problems. Also, they don't smoke or leak, although the cork oil pan gaskets do seep. They are not driven below 32 F and are stored in the winter at 55F. In looking at the original owners manuals for the cars, the typical oil recommended for normal use, between 32 and 90 or so Fahrenheit is 10w-30, for below freezing a 5w can be used, while in hot temperatures, 10w-40. So my question is: Why the emphasis on the heavier weight oils such as 15w-50,20w-40, 20w-50. Honestly, if it was not for this site, I would just buy 10w-30 Pennzoil or Mobil 1 and be done with it, but there's so much discussion here about zinc, phosphorous and heavy oils, you all have put doubts in my mind. So any help is appreciated.

 

[JAG]

I’d probably use this oil or a similar product from another brand: http://rotella.shell.com/products/full-synthetic-and-blend-oil/t5.html
Reason being is that it’s a good oil at a good price on the up half of the recommended viscosity grade.

 

[ka9mnx]

Originally Posted By: Building3
Thanks for your thoughtful replies. My couple of classic/muscle cars are all factory spec whether stock or rebuilt so I can rule out the high lift/high pressure situation. They are all "broken-in" so I am not worried new engine problems. Also, they don't smoke or leak, although the cork oil pan gaskets do seep. They are not driven below 32 F and are stored in the winter at 55F. In looking at the original owners manuals for the cars, the typical oil recommended for normal use, between 32 and 90 or so Fahrenheit is 10w-30, for below freezing a 5w can be used, while in hot temperatures, 10w-40. So my question is: Why the emphasis on the heavier weight oils such as 15w-50,20w-40, 20w-50. Honestly, if it was not for this site, I would just buy 10w-30 Pennzoil or Mobil 1 and be done with it, but there's so much discussion here about zinc, phosphorous and heavy oils, you all have put doubts in my mind. So any help is appreciated.


Building3,

Lots of opinions here (including mine) and not much facts. Some come with experience (if it's solid) which can trump science.

I think you have come to the correct decision, though. 10w-30 and call it a day...

 

[Scdevon]

Keep in mind that flat tappet cams were never "broken in" on the assembly line, nor was any "high zinc" assembly lube lovingly smeared over every square inch of the cam and lifters on factory assembly lines. If you were lucky, a fixture dribbled some normal bulk engine oil on the lobes and journals and in it went. "Run it at 20 minutes at 1500 rpms during break in"? Are you kidding?

I'm talking about typical Ford / GM / Mopar V8s from the flat tappet cam heydays and there were some pretty aggressive stock cams in the late 1960s to 1971 or so. A Chevy LS6 (for example) had a "stock" .520 total lift cam with 316 duration. This was hardly a weak cam and they never did anything special to break them in.

We never "broke in" replacement flat tappet camshafts at the GM dealer I worked at when that bad batch of 305 cams was going around. You dumped 5 quarts of bulk 10w-40 and a can of GM / EOS in the crankcase and down the road it went. We never saw any of them come back either once an updated cam was installed.

 

[Gokhan]

As I said earlier, a modern 10W-30 is probably fine but go with Mobil 1 15W-50 for added protection, as it has a thicker base oil and more ZDDP and moly. It's a question of how long you want your engine last. You can also do UOAs and see how much difference it's making. Perhaps, it doesn't, as experiment doesn't always agree with theory.

 

[Building3]

Gokham: If the engineers specified 10w-30, they would have specified an oil pump appropriate to that oil. Would that oil pump be able to pump a 15w-50 or 20w-50 too? It seems quite thick. Would they have tested for it. Any thoughts?

 

[OVERKILL]

Originally Posted By: Building3
Gokham: If the engineers specified 10w-30, they would have specified an oil pump appropriate to that oil. Would that oil pump be able to pump a 15w-50 or 20w-50 too? It seems quite thick. Would they have tested for it. Any thoughts?


Yes. The effect of TEMPERATURE on oil is far more significant than the difference between grades at 100C.

 

[Gokhan]

Originally Posted By: Building3
Gokham: If the engineers specified 10w-30, they would have specified an oil pump appropriate to that oil. Would that oil pump be able to pump a 15w-50 or 20w-50 too? It seems quite thick. Would they have tested for it. Any thoughts?

As OVERKILL said cold oil is a lot thicker anyway.

Old cars spec anything from 10W-30 to SAE 50 according to the ambient temperature.

Isuzu Holden Rodeo TF oil-recommendation chart:

Classic-BMW oil-recommendation chart:

1984 Porsche 911 oil-recommendation chart:

Australia Mazda and Prius oil-recommendation chart:

OEM oil recommendations from around the world (link)