Bad cam

A few years ago someone sent me a damaged race cam. It was a flat tappet cam using stock lifters. It was not one of my cams and I'm not saying who they bought it from other than it was hardwelded. They were using RD dual racing valve springs with no coil bind (installed height checked around .330"). Redline 20-50 racing oil. The lifters looked fine even after the damage but the cam went to shit on every lobe on the closing flank side of the nose (near the nose) and over the nose on the worst lobe.

They bought a new cam and the same thing happened. The cams were made years apart. It was an 850 and the revs were limited to about 7000RPM.

I haven't seen this happen on a hardwelded cam and never had this kind of problem in my own racing. Its not wear - more like flaking or pitting. There are residual islands in the bad areas that are still in tact. Anyone else have this problem on a hardwelded cam?

Never used a hard faced cam but the damage looks similar to fatiqued sintered bearing failure. The forces from the journal breakdown the bonded powder structure of the bearing so the original particles are loosened and leave pockets once they depart completely. Its caused either by overloading from incorrect design or weak sintering where the bonds are weak between the particles. This suggests the original hardface welding was powder metal based eg plasma or HVOF.

Looks like galling. You can see what appears to be ever so slight metal pickup to the bottom left of the galling. The actual pock marks look like the result of brinelling failure; just guessing it is a result of metal fatigue (no sh*t), the question is why. It could be inappropriate hard facing material properties. I don't recall ever seeing this much on a cam but have seen this on at least one main bearing (NJ306E).

To the lower right of the galling looks like what appears to be dimpled or scalloped grinding marks left over from the manufacture. It could be grinding chatter or poor dressing of the grinding wheel.

Dances with Shrapnel said:

Looks like galling. You can see what appears to be ever so slight metal pickup to the bottom left of the galling. The actual pock marks look like the result of brinelling failure; just guessing it is a result of metal fatigue (no sh*t), the question is why. It could be inappropriate hard facing material properties. I don't recall ever seeing this much on a cam but have seen this on at least one main bearing (NJ306E).

To the lower right of the galling looks like what appears to be dimpled or scalloped grinding marks left over from the manufacture. It could be grinding chatter or poor dressing of the grinding wheel.

Click to expand...

Yeah I see what looks like imperfect grinding but it's not visible to the eye or under magnification so I think its some weird reflection in the photo. Many cams are made on older equipt with old cam master plates. I talked to John Andrews of Andrews products and he could make them out of 52100 or maybe S7 steel on modern CNC machinery but he needs high minimums and a big investment to cut the helical gear. Newman cams in England has the same equipt. Neither do hardwelding and so far hardwelding seems to last the longest (except the cam in the photo).

I have seen that sort of pitting on some kawasaki 4-cylinder cams that came from the supplier not properly hardened. Sometimes it is harmless and hopefully the oil filter picked up the flakes of lobe surface.

I've seen a couple of Norton race cams that failed because the wrong hardfacing rod was used (by mistake, not intentionally), but they didn't look like this one. The wear was more like what you see when a stock cam that isn't hardened properly wears, where the lobe is just worn away at the peak of the lobe.

Ken