<VV> cam and lifter wear

[Mark Durham]

Ray, in short, the cam is the highest stress area in the engine, and
normal oil will not protect, it breaks down. So the oil and car
manufactuers decided to put zinc and phosphorus in the oil which
burnishes into the pores of the metal when each cam lobe rub happens,
and provides a wear layer for the next cam lobe rub. It makes the
metal slicker on the lobe and the lifter face.

Synthetic oils will not break down like petroleum oils,however, they
can get swiped off the lobe which is splash lubricated, so here too,
the best bet is to have the ZDDP there to wear in and rub off.
They redesigned the cam and follower setup on our modern overhead cam
engines, so they do not need as much ZDDP to protect the cam.
Mark Durham

On Sat, Feb 26, 2011 at 3:05 PM,  <djtcz at comcast.net> wrote:
> ----- Original Message -----
> From: "Ray Rodriguez III" <vairguy at echoes.net>
> Subject: <VV> a different oil conversation
>
> ................. but I'd like to know exactly where and why this ZDDP is needed and exactly what happens (and how) if you don't have it.
>
> I've heard talk about wearing cam lobes down... but not sure if that was only relative to break-in or a problem contributed to by a lack of ZDDP.
>
> Ray "Grymm" Rodriguez III
> ------------------------------
>
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> The foot of the Lifters (tappets) and can lobes live, and die together. C am wear is not reverseable, and once begun usually progresses rapidly. T hat surface has the highest loading (PSI) and sketchiest lubrication of any part of the engine.
>
> Tricky geometry (tapered cam lobes and a subtle radius on the lifter feet) is used to promote lifter rotation
> http://lh6.ggpht.com/_T17qmiZWUoA/TL1kOrw63hI/AAAAAAAAAkU/HYgxRF7mb-8/s640/CamTaper2.jpg
>
>
> "Break in" is critical to survive while developing smooth rubbing surfaces necessary to help develop an oil film during normal operation.
> Even nicely broken in cam lobes and lifters need help from time to time. ZDDP and other sacrifical anti-wear additives are there to kick in when contact goes metal-to-metal.
>
>
> It's not easy to lubricate the lifter/cam interface adequately when the cam action gets very frisky at all.
> "In the mid 1950s, Chrysler and Oldsmobile engaged in a horsepower race using high-lift camshafts, and both experienced camshaft scuffing and wear problems. These problems were overcome by better metallurgy for camshafts and lifters, phosphating the camshaft and increasing the level of ZDP to 0.08 percent."
>
> ref - http://www.studebakercarclubnsw.com/workshop-oil.html
>
>
> ":We were failing camshaft lobes in the first 20 minutes of engine operation. It took several months of 24/7 laboratory work at Central Engineering to solve this problem. We eventually changed tappet material, added a special coating to the tappet face, changed tappet and cam profiles to promote tappet rotation and added an anti-scuff additive (ZDDP) to the break in oil. We solved the problem - which was so serious that it threatened production of the Firedome V8 engine.”
> http://www.allpar.com/mopar/hemi/chrysler-hemi.html
>
>
> cam/lifter/tappet wear picture nightmares
> http://image.hotrod.com/f/9172975/HRDP_0606_01_z+flat_tappet_cam_tech+broken_lifter.jpg
>
>
> http://lh6.ggpht.com/_T17qmiZWUoA/TL1kOrw63hI/AAAAAAAAAkU/HYgxRF7mb-8/s640/CamTaper2.jpg
>
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