An Abberation in Cam wear

[Dynomite]

With several posts recently discussing Camshaft wear on associated mating surfaces (Head and Cam Cover)......here is a new aberration to think about ;)

This is a low miles (less than 30K) stock 90 Head.

The tips of all the cam lobes (8) on one intake camshaft (the other camshafts have a perfect wear pattern) of one head are shown here. Can this be explained in terms of cause and effect?

The two photos are taken on drivers side Head with front of engine toward the right.

The lifters related to this camshaft seem to have a normal wear pattern.

https://cimg0.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/500x500/80-img_0451_7b058480b844f161089c92db121af4c24529c641. jpghttps://cimg1.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/500x500/80-img_0454_a551edd9e441c27277f5c7e106cabb743514fa8c. jpg

Post 294 - Camshaft Abnormal Wear (https://www.corvetteforum.com/forums/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-15.html#post1596384619)

[93 ZR1 Barcelona]

When I removed the camshafts of my 93, with 90 K miles on it, some of the intake lobes showed also this kind of pitting at the edge of the lobes, like the ones you show in the pictures. I think 2 or 3 lobes, not all.

All lifters were OK and I had reinstalled them in their original positions (very important this, not to mix them) at assembly.

I reused the camshafts without problem when I assembled the engine.

I assume, that this pitting is due to galling of the cast metal of the camshaft in interaction with the steel of the lifters when extreme pressure is applied to open the valve...that maybe could be solved with engine oil with a higher zinc contents to lubricate the lobe..don't know.

This cam pitting doesn't happen with the engines with roller lifters.

[Pete]

Wow,the last picture right lobe looks bad how does it feel is it deep? if you use Scotchbrite on it will it smooth out?

The one in the first picture left lobe i have seen this before no issues unless it's a deep groove,the only thing i can think why this one if like that maybe some dirt got in there.

What i have seen on low mileage motors that have not run for a while with some condensation the lobes and lifter had rust at the area the lobes stoped and touching the lifters is where they were rusted on the cams i used Scotchbrite (green sponge stuff) they cleaned up nice replaced lifters.
Don't worry you won't hurt the cams they are hardened as far as .250

If the cams clean up good then your good to go,otherwise they will make good regrinds.

Pete

[Pete]

Thanks Pete :thumbsup:

Did these cam lopes ride flat on the lifter and if so....why did they not shine up on their own? The lifters look fine.

Just wondering.....I will give cam lobes the scotchbrite treatment.
These are extra complete Heads I have just in case I want to try something different ;)


No,they don't ride flat they have a tapper.
I started to write that in my previous post i accidentally hit wrong button and lost all the info freaken PC's oh well.

Pete

[scottfab]

With several posts recently discussing Camshaft wear on associated mating surfaces (Head and Cam Cover)......here is a new abberation to think about ;)

This is a low miles (less than 30K) stock 90 Head.

The tips of all the cam lobes (8) on one intake camshaft (the other camshafts have a perfect wear pattern) of one head are shown here. Can this be explained in terms of cause and effect?

The lifters related to this camshaft seem to have a normal wear pattern.


Did you use Amsoil ?

[Marc Haibeck]

I first saw a lobe with that wear pattern about ten years ago. The worst thing about it is that the lobe is actually pitted or maybe chipped on the high end of the tip. Since then after having the cam covers off of maybe 100 engines I have seen it about two additional times. We put those cams back in service long ago and there has been no repercussion. I would not be too concerned about it.

My theory as to what is happening. I wonder if the lifter is lofting and then smacking back down on the lobe. If that is the case, excessively long time with engine speeds over 6000 rpm or a weak valve spring could promote the problem.

[scottfab]

... snip...
The only possible abberation in normal function of any of the four camshafts I can think of would be camshaft timing wherein the intake camshaft on the drivers side was timed different than the other camshafts. Or.......that lubrication of that bank of cam lobes was different than the lubrication of the cam lobes of the other camshafts.

...snip...


Do you know the history of the motor the heads came off of? Damaged? Noisy?

FWIW on occasion I've run low on oil a few times (below the add mark) and on those times it's the drivers side lifters that let me know.
Also back when I use to run regular non synthetic oil (90s were not shipped with Mobile one) I could tell when it was oil changing time by the sound of the drivers side lifters.
One wonders if I might have the same lob wear issue? hmmmm