Flat tappet cams and todays oil NO GOOD!

[EagleMark]

Finally found a writeup of the hows and whys oil on shelf today is destroying old flat tappet cam engines.

http://www.corvettefever.com/techart...nes/index.html

[1project2many]

There is quite a bit of discussion about this on bobistheoilguy.com. The discussions there can get pretty technical but it's still possible to sift through to find recommendations for good oil for older engines. My Toyota pickup engine has been on Delvac 15W40 since I built it and the engine in my '57 gets NOS oil that I bought a few years ago when a local store was clearing it out. I'm always on the lookout for old, dusty bottles (or cans for the really old guys) of oil to keep in my inventory for the old engines in my vehicles.

[EagleMark]

I've read stuff over there at bobistheoilguy.com and agree quite technical. I've been aware of this issue for at least 10 years because of involvement with oil testing in Harley air cooled engines in desert heat from years ago. But the link I gave was an easy to read with numbers and history that everyone could understand.

Another interesting fact was when I was testing oil for Harley Davidson in the desert summer conditions in mid 80's the viscosity testing of different oils resulted in Harley Davidson oil being almost identical to Kendall oil which was sold in all the VW and Sand Rail shops. It was later reveled that Harley Davidson oil was purchased from Kendall. Kendall was sold and is now Brad Penn Racing oil which has now become oil of choice at VW and Sand Rail shops. It is also one of the few oils with Zinc and Phosphorous levels for flat tappet cams and recommended by Isky today for their flat tappet cams.

I've given up the multiple oil thing and searching years ago and only have Amsoil 10w/40 Synthetic with added Zinc and Phosphorous for everything.

And yes I'm old and remember cans of oil that required a spout to pierce the can to pour it in the engine... you know the ones you see the guy on American Pickers collects...

[RobertISaar]

wife's 90GP w/3.1 is a flat-tappet engine, still seems to run fine on even the SN rated oils.

then again, it's cam is best described as "mild, on a good day".

the 93-99 Northstar and 91-97 LQ1 are a couple of DOHC i can think of that are also flat-tappet, but radically different obviously.

[EagleMark]

Todays off the shelf oil is just not right for flat tappet cams, below borderline at best, weak valve springs and mild round cam lobes would also come into play. But if you wanted her cam to last it would need correct oil or additive.

I'd be curiuos what the 93-99 Northstar and 91-97 LQ1 DOHC factory specs are on oil? Back then oil was fine. Not today.

Last engine made with flat tappet cam was 2006 Jeep 4.0L engine, last year for that inline six era engine. It required Chrysler oil or Chrysler additive or oil with matching specs or warrenty was void on cam in engine. Maintenece reciepts were also required if camshaft failed. Big problems with last years of a real Jeep to an un-informed owner.

[RobertISaar]

not sure what the API certs were at the time(i'm sure it's searchable), but all LQ1s were recommended to have 5W-30, all 93-99 Northstars recommended to use 10W-30. the 00-up northstars went to a roller design.

also: that car is somehow being sold, even though it's a total rotbox. i guess the inflated prices of the used car market does have an upside. :D