OZ951

Here are some camshaft pics with similar wear patterns on each lobe. Is this type of wear normal ? Have many of you seen similar wear on the 951 motors that you have pulled apart ?





Wayne

Larry Parker

Is that wear or just a bit of discoloration?
my car has a bit of that on both my cams...I would assume that the shiny areas are the ones where the wear is.......dark must not make contact with the lifters.........

OZ951

The wear that I was referring too is the dark patches either side of the tip of the lobe(s) - but only on one edge of the lobe.

I am not sure how the cams are constructed but it looks like there is a top layer on the lobes and the wear patches seem to be worn through that to a darker material below.

Wayne

Danno

It looks like the dark spots on both sides of the tip of your cam lobe is parts that don't contact the lifter. Due to the ramps that build up the lift, you can actually have little contact with the lobe right after the tip. Is your cam stock?

Typically cams are nitrided for wear-reistance and this is a dark coating. Then as it wear out, the worn spots are shiny. That's the difference between say.. the tip of the cam lobe (which gets the most wear) and the base circle on the oppposite, which has little pressure & wear.

Luke

bump

OZ951

Thanks Danno,

The crank is stock so far as I know. I guess what I am calling wear spots is more likely to be the low spots which are not making contact with the lifters - hence they are more than likely the ""no wear" spots.

So would that mean that the pattern I see is a result of the profile on the cam lobes rather than some sort of unusual wear?

So who else has found their cams look like this ?

Wayne

Tabor

Mine did at ~100,000 miles.

OZ951

Tabor,

did you reuse the cam as it was without any problems ? If so - how many miles have you done on it since ?

Wayne

Tabor

Yea, I reused it. I have done another 25,000 miles since.

OZ951

Thanks Tabor,

thats good to know.

Cheers,
Wayne.

Tabor

Oh yea, my 968 engine that is supposed to have 56k on it also has similar cam wear (though not to the same extent).

Perry 951

Both cams I have look the same.

It is nothing.

OZ951

Thanks for your input also Perry.

I was told originally that the "wear" patterns were not a problem but as any long-term user of this board would know, there does tend to be some inaccurate information around as people relay what they have heard and some things develop into urban legends with not a great deal of supporting fact. SO I kind of like to confirm people's actual experiences from time to time. Still, these boards are such a valuable resource - owning a 944 without access to discussion boards like Rennlist and the people on them, would be a completely different experience.

Aplogies for the drift off topic.

Wayne.

rplencne

Actually, even if the lobe is worn, as long as it's worn evenly around the circumfrance of the lobe, it shouldn't effect on the lift/duration very much ... if any. The "slop" that is created by the lobe wearing is taken up in hydraulics portion of the lifter. One could even argue that if the heal of the lobe wore faster that the peak of the lobe (which is extremely unlikely ... they tend to wear evenly) that you could actually have the lift value increase.

-Bob P.

Danno

Yeah, that would be nice, but unfortunately cams wear out the most at the tip of the lobe. The base circle no-lift area typically has very little wear. Even after 100k-miles, it may still be dull with some of the original machining lines still visible.

One 'cheater' way of regrinding cams is to grind away the base circle without touching the lobe itself. This gives you a greater difference between the tip of the lobe and the base circle, giving you more lift. Your lifters needs to have the travel required to extend this extra distance though....