Pitting on CAM?

I'm in the middle of an engine rebuild and I've found two things I really don't like.
1st is pitting on the cam. Never seen this one before. You can feel it and see it on the edges but not on the lobe itself. I'll try to get a good pic of it but the cam is still in the block.

2nd is a trashed piston. The top edge looks like it was blown into the head area, or like it was peeled up in one small spot smaller than a dime. It put a line in the cylinder wall that is just able to be felt. That will have to be bored out more than likely. (doubtfull I can just hone it)

I thought about using this engine for stock rebuild to replace a dying engine in my XJ right now (or even a very mild stroker) but now I'm not so sure.

So my Question. Is the cam still usable?

I really have no desire to go with a hotter cam, I don't have the funds to throw at building an engine. I want a reliable engine to put into my XJ.

Pitted cam lobes are probably due to corrosion. Comes from sitting for long periods of time in aircraft engines where it is common.

The description of the piston is either detonation or a little F.O.D. from something sucked into that cylinder. Got a pic?

Without seeing the damage/wear on the cam, I'd have to say measure the lobes. if they all still have the proper height, and there's no galling on the surface, it could be reused with the original lifters.

Overdriven said:

I'm in the middle of an engine rebuild and I've found two things I really don't like.
1st is pitting on the cam. Never seen this one before. You can feel it and see it on the edges but not on the lobe itself. I'll try to get a good pic of it but the cam is still in the block.

2nd is a trashed piston. The top edge looks like it was blown into the head area, or like it was peeled up in one small spot smaller than a dime. It put a line in the cylinder wall that is just able to be felt. That will have to be bored out more than likely. (doubtfull I can just hone it)

I thought about using this engine for stock rebuild to replace a dying engine in my XJ right now (or even a very mild stroker) but now I'm not so sure.

So my Question. Is the cam still usable?

I really have no desire to go with a hotter cam, I don't have the funds to throw at building an engine. I want a reliable engine to put into my XJ.

Click to expand...

Have you pictures?

Honestly, the full face of the cam lobe does not make contact with the lifter foot - just a narrowish band a bit off-centre. If you look at the face of the cam lobe, you'll see that it's not fully "square" to the body - it's got a slight taper to it. This matches up with the foot of the flat tappet (which isn't truly "flat" - it's got a slight crown to it. A circle about three feet in radius, I believe...) which enables the tappet to rotate in the bore. This is why flat tappet cams can't be used with roller tappets - you'd wear out the roller in remarkably short order.

This rotation is necessary to the longevity of the tappet.

If you check the cam lobe under magnification, you can probably see the "wear band" where the tappet foot makes contact. As long as the pitting around the edge doesn't touch the wear band, you're going to be fine (although I do suggest new lifters. New lifters on used cam OK. Used lifters on new cam BAD. Mixing lifters among cam lobes VERY BAD.) The "pitting" isn't probably related to any material failure anyhow - cam blanks are usually cast, and it could just be a casting void that broke loose during engine run-in...

For the piston issue, I'd have to see it.

If the spot on your piston is kind of a burn and melt type thing and right under the spark plug, it may be from the wrong plugs. A faulty (partially plugged) injector or a vacuum leak on the cylinder or a combination of all of the above.
Pretty common over here, they run them pedal to the metal for hundreds of miles. Run them too lean and the piston melts, run a hotter plug and it burns a pit. Many of the early XJ's were delivered to Europe with colder plugs.