Xotni

Hello, everyone! First off, sorry if this has been asked a bazillion times. I figured my own thread might serve me better for the information I'm seeking than digging through the forums. Forgive me if I'm wrong!


Long story short, I've had to pull the motor (4.0L S6) out of my 2000 XJ Sport to replace the cam because it got shot due to installing new lifters when replacing that dreaded #0331 cylinder head. (As luck with had it, I bought it with a cracked head. Didn't know until researching my particular 4-wheel drive system that the problem even existed...)

Apparently luck was not with me when reading about new lifters on old cams being okay if you broke it in properly. Either that, or it just wasn't done properly entirely.

Since I wasn't around when the new head/lifters were installed and the vehicle was initially started, I have no idea if the break-in was done correctly; whether we're talking about the RPM-to-time was done or if we even used the correct oil for a break-in.

So that brings me here. Everything else, so far, looks good in the motor. Mains are... surprisingly good looking, for everything else that's been wrong with it. Not sure how the cam barrings look yet, as I haven't pulled the old cam from it. The only thing I'm really worried about at this point is the break-in... which leaves me wanting to ask you guys these questions:

1. For how long and how many RPMs have you all had good luck breaking in cams? I know this varies depending on who you ask, but I'd rather ask people who have experience with this particular motor, which I'm sure a lot of you do.

2. Oils... as I understand it, today's oils do not have the necessary levels of zinc to fully protect a flat-tappet cam. Is this the case? If so, what do I need to invest in to keep it protected during and after the break-in? Are additives where it's at, or can I use just a different kind of oil and be fine? (A side-note here: I used an additive when replacing the oil after the new head installation, but it was either apparently not enough, too much, or it just wasn't broke in like it needed to be.)

2b. Also, are synthetics safe to use in this motor, due to the zinc contents? I would think so, but I am admittedly not very mechanically inclined, which is why I'm here.

3. After the break-in: how long should I run with the break-in oil before replacing it, and what oil should be used afterwards?


Again, sorry for these questions... I hate to think how many times you guys have seen this. But I'd like to avoid having to have this Jeep parked for months again because I had to save the money to replace another cam, lifter set, etc.

For reference, everything on the Jeep is stock, aside from a high-flow exhaust that was installed with the new head. I'd intended to go through with a high-flow muffler/filter after it was running again, but it did not take long at all for the cam to go out after the head/lifters were installed... which makes me think that when all that was done, the break-in was not done correctly in one way or another.

Also, I'd only really be driving this vehicle back and forth to work every day, and maybe occasionally a random 40-50 mile trip to the next county over. No mountain climbing or forest ranging for me.

Once more, sorry for this, but I highly appreciate any and all info you could all give me on this!