The
following article was written by a member of the Ariel Motorcycle Club,
and reproduced with permission. It appeared in the Jan/Feb 2006 issue of
their newsletter, Spirit of the Air.
Minimizing
Camshaft & Lifter Wear
By
John Havel
For those members who don't know me, I've been a club
member for over 30 years, but because I live in the East, I'm seldom seen or
heard from. I retired five years ago after spending 38 years as a mechanical
engineer working with internal engine components where lubrication is a prime
concern.
I still consult for my former employer and I thought members might benefit
from something I recently learned about current motor oils from one of my
former colleagues.
Because modern automotive engines now use roller cam followers in place of
"Flat tappets, the amount of anti-wear' additives in
motor oils has been significantly reduced. This makes them less
suitable for use in our old motorcycle engines with their "Sliding" cam
followers.
This is also causing a problem for automotive engine re-builders who still
rebuild older engines with flat tappets.
Cam
and lifter failures, especially during the critical break-in period, have
increased.
Zinc and Phosphorous are the most popular and commonly used "EP" or
"Extreme Pressure" anti-wear additive
elements. They are present in high concentrations in greases and gear oils
to prevent wear and galling between mating surfaces under extreme
loads. In the past these were used in higher concentrations in motor oils when
most engines were built with flat tappets. Because these metallic elements
eventually find their way into the by-products of combustion in worn engines
and cause contamination of emission control components, they have been
greatly reduced in the most recent oils intended for use in engines with
roller cam followers.
The American Petroleum Institute, or "API" for short, has devised a
classification system for oils based on their suitability for various types of
service. These classifications, found in the round donut symbol on the back
of oil containers, run in two series: "S" classes for Spark ignition
engines and "C" classes for "Compression" ignition
(Diesel) engines. The classes start with "A" and progress through
the alphabet as newer classes are added. Class "SA" through
"SH" and "CA” through "CE" oils are now obsolete.
The most recent "SM" class oils only contain a little more than half
as much Zinc and Phosphorous as the "SH" class oils which were
originally introduced for use in 1996 model vehicles.
Most of the motorcycle engines I've disassembled have exhibited some degree
of cam follower (lifter) wear and frequently this extends to the cam lobes as
well requiring either regrinding or replacement of both components. In my
experience the Ariel Square Four seems to be one of the worst offenders. We've
always been told frequent oil changes and use of a "Good grade" of
oil will help, and that's true.
So where is all of this leading us? If you're using an automotive grade oil
with an API Service classification "SL” or
"SM," you're probably not receiving the level of anti-wear
protection you think you are. But there is hope.
There are still oils on the market that contain higher levels of anti-wear
additives. These are typically oils intended for diesel engine service. They
carry
the API Service Classes "CE" "CF-4,"
"CG-4," "CH-:4," and "CI-4." Three such
oils are Chevron "Delo 400," Mobil "Delvac" and Shell
"Rotella T." These diesel oils typically come in 15W-40 viscosity
although other grades with the above API classifications can also be found.
This should be acceptable for motorcycle engines. I've personally used SAE
20W-50 in my Square Four and Matchless twins for years and there really isn't
much difference till your oil gets above 210 degrees F. I rode my 57 Sq-4 for
20 miles at 8O MPH on an 85 degree day and couldn't get the oil to 200
degrees.
Zinc and Phosphorus are the most significant "EP" ingredients but
not the only additive elements used. Others are Boron, Calcium, Magnesium and
Molly, some or all of which are used in the above oils. Many
"Racing" oils, which typically carry the disclaimer "FOR OFF
ROAD USE ONLY," also contain significantly higher anti-wear content.
Quaker
State
"Q-Racing" full synthetic is one, although that's an expensive
alternative unless you're already committed to using synthetic oil.
Although I don't generally recommend oil additives, there are products
intended for use for assembly and break-in for engines with flat tappets
that contain high concentrations of EP additives. One of these is GM's EOS
Assembly Lube available from GM dealers under PIN 1052367 (16
oz. for $8.72). Although the bottle specifically states this is not an
additive, I am aware that there are people who have been successfully using it
as an additive for years. I'm confident it can be used safely at rates between
two and four ounces per quart as an addition to
help boost the anti-wear properties of "SL" and "SM"
classed oils. This product is about the same viscosity as straight grade SAE-50
motor oil. It should readily mix with the
rest of your oil, but if you are concerned, you might want to premix it.
Another assembly lube you might try when
building an engine is “Clevite Bearing Guard.” It
has a thicker consistency than the EOS product to help keep it in place. It
becomes fluid at about 100 degrees and readily mixes with all oils. It's
available at all NAPA Auto Parts stores under part # CL-400
(4 oz. for $.99) or part # 2800-B2 (8
oz. for $4.99)
Older spec. automotive oils with their greater anti-wear content are now
obsolete. I would highly recommend you try either EOS as an additive or one of
the oils mentioned above. However, be aware that the diesel oils are likely to
change
in the future, so pay attention to the API Service Classification. As long as
the ones mentioned above are present you should be OK with these oils. The
assembly lubricants mentioned are known to contain a high concentration
of anti-wear or "EP" compounds intended to
prevent
camshaft and lifter wear. Other products labeled "Assembly Lube"
and specifically intended for camshaft and lifter break-in should also contain
these compounds, but I just wasn't able to research all of them. If you decide
to research other oils, you should look for oils that contain at least 1200
ppm (parts per million) of Zinc and at least 75% as much Phosphorous as Zinc.
I hope this will help you preserve some of those hard to replace internal
engine components in your Ariel and other motorcycles.