Camshaft lobe wear (grove

[D.Martijn]

Hey guys,

Last week I re adjusted my valves and noticed a some wear on the lobes of my cam. I could lightly feel the difference in height when I went across it with my finger nail.

I'm now wondering if this is normal for these +150mile engines or if I should replace the camshaft.

If I should replace it, my second question is, should I go with a used one with no wear, a new OEM one (although expensive, 570€)? Or an aftermarket one (febi..?)?
I already found a new Kolbenschimdt camshaft in Germany for 225€, were these used from factory or did BMW make the camshafts themselve?

Please give me some advise, appreciate it :)

[ForcedFirebird]

This is common. I found a few things that cause it. Thin modern oils don't have zinc in them, so very high mileage m20's can wear. An accelerated way I have seen was a cracked head that was run for a while. The coolant in the oil made it lose viscosity and the came was worn much more than yours after just a few miles.

[15Michaeljoseph]

After 150k, wear is to be expected... Especially if the PO(s) weren't religious with oil changes and maintenance. I don't think it has so much to do with lack of zinc (ZDDP) in the oil as it does people not keeping up on their oil change intervals. The oil industry has come far enough where they've phased out a lot of ZDDP for emissions related reasons, but have replaced those old additives with new ones.
I did a lot of research on this after rebuilding my M20 (and I'm extremely paranoid and anal about this kind of thing), and the only oil I would trust in my car from here on out is Mobil 1 synthetic, either 0w-40 (I live in a climate that sees colder temps but this weight is good for hotter temps too) or 15w-50 (which supposedly contains more ZDDP out of the bottle, if you really think you need it)

Now, as far as your cam question, I'd say you want to replace it with a new aftermarket unit. Rebuilding a head is a big expense, and isn't the kind of thing you want to buy used parts for... Which is a mistake I made once, and never again. My rationale is this:

Over the lifetime of the engine, the cam and rockers wear into each other, kind of like brake pads and their rotor. When extreme wear occurs, like in your case, deeper grooves develop, where the rockers end up with moon shaped wear patches and the cam grinds itself down. If you throw a 'better' cam in there, it's either going to machine itself the way the old one did to match the rockers, or it's going to greatly accelerate wear on the contact patch of the rockers, putting a lot more metal shavings in the oil and just generally wearing them down more. It's just a messy situation.

The second thing to understand is that these parts are obviously designed for contact (not directly, but with a thin film of motor oil in between them), and as a result are case hardened from the factory. That basically means that the metal outer surface of a new cam or rocker is much harder wearing than the inner metal. Think of a crusty loaf of bread. So as the outer metal wears down, the wear accelerates regardless because the inner metal is softer. If you can feel a ridge in the cam, you can trust that it's pretty much shot.

My recommendation (based on experience with my own car) is to go with a brand new aftermarket cam (because BMW hardly makes any of their own parts, it's all outsourced, especially with a car of this vintage) but also brand new rockers as well.

Do it once, and do it right. Spend the money. As far as I know, Febi is the same thing you'd get if you bought from the dealership. When I redid my head, I went with new Febi rocker arms and new eccentrics (the adjustment piece). I tried to order a new Febi cam, but they were back ordered, so I was sent an "AE" cam by Federal Mogul. (Seems to be the same as a febi).



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[SkiFree]

After 150k, wear is to be expected... Especially if the PO(s) weren't religious with oil changes and maintenance. I don't think it has so much to do with lack of zinc (ZDDP) in the oil as it does people not keeping up on their oil change intervals. The oil industry has come far enough where they've phased out a lot of ZDDP for emissions related reasons, but have replaced those old additives with new ones.
I did a lot of research on this after rebuilding my M20 (and I'm extremely paranoid and anal about this kind of thing), and the only oil I would trust in my car from here on out is Mobil 1 synthetic, either 0w-40 (I live in a climate that sees colder temps but this weight is good for hotter temps too) or 15w-50 (which supposedly contains more ZDDP out of the bottle, if you really think you need it)

With all due respect Michael, you are off base on this.

Oils are very much an integral factor into premature wear issues (and 150k is certainly premature.) I've taken apart/built/maintained dozens of m10,m20, and m30's (and forcedfirebird has done the same, if not more). Here's a little write up...

https://docs.google.com/document/d/1ah2BnevhU2I4yWBfE0ZMCtIA54qrh5DTo06y_1i29H4/edit?usp=sharing

Your other advice is great though.

OP, in addition to the other advice, be religious about your valve adjustments. If you are getting new rockers (and opt to NOT run HD rockers), then take the extra time to grind down the stress risers (casting ridge and logo imprint) on the eccentric forks.

BTY, the wear in your photo isn't bad. Just be consistent with your oil changes and valve adjustments.

----------------------------------------

Quick story about engine break-in:

1) Had a client racing a 2002/M10 in the Monte Carlo Historic Rally.... sent him a new "race head". He adjusted the valves FIRST and then bolted it on. Nearing the end of the rally he started to hear valvetrain noise and pulled the cover off. The valve stems were mushroomed, the rocker pads worn, and the valve lash...well there wasn't any. The problem was that once the head is bolted on the valve lash gets tighter, combine that with the fact that the seats/valve job was new and they hadn't fully bedded in yet. All this with the engine run hard for three days straight. Moral of the story is to be sure to check the valve lash once bolted together, once after the first couple run times, and once after a couple hundred miles... then carry on with the normal routine.

[D.Martijn]

Thanks for all the info guys!

I might hang off a little longer with a head rebuild as it's my daily driver so I have to plan the rebuild a bit more.
I'll probably still go with the Kolbenschmidt camshaft as I'm not the biggest fan of Febi though.

The previous owner had the cylinder head replaced with a AMC head, if I remember correctly he switched over the camshaft and rockers from the original head as those were still in good order. So there was probably some coolant in the oil. That might explain some of the premature wear?

@SkiFree, I've heard there were a few instances were the HD rockers had pads falling off?
Do you still recommend these? Or should I go for the OEM/Febi ones?

[Dano 1]

Having just rebuilt a head I can add a couple thoughts.

If the car is your daily, it might be worth looking into a good used head core that you can build on the bench and just swap on. Depending on how many parts you want to reuse it could be more efficient to have machine work done on another casting and bench build it, then just swap one for the other. Depending on your skill level swapping heads shouldn't take much more than a weekend or a few evenings.

If you have that much wear on the cam there's a good chance your rockers/rocker shafts are worn as well. A simple check to do is to pull the valve cover, rotate the engine/cam following the lash adjustment procedure, remove the corresponding rocker clip, loosen the adjuster eccentric and attempt to twist the rocker perpendicular to the shaft. There should be little to no play and if there is your shaft or rocker bearing(s) are worn.

I agree with SkiFree on the oil notes, I would seriously look into a high Zinc oil or Zinc additive especially when breaking in a new cam/rocker setup. This is especially problematic (at least in the states) with much older vehicles with flat tappet cams, I've heard enough horror stories about wiped out cams/lifters to be mindful of Zinc content.

[15Michaeljoseph]

Just a follow up on this, and another option.
STP makes a very widely and cheaply available product simply called "STP oil treatment", made from a very thick synthetic base stock oil, and ZDDP additive. I've read that it comes in two kinds, a thick 8cyl version and a thinner 4cyl version, but so far I've only ever seen the 8cyl version on the shelves. It's been around since at least the 70s, and a lot of muscle car guys swear by it so it must do SOMETHING. If you decide to try it out, make sure you don't get the kind that designed to stop leaks or whatever because that'll cause damage to the integrity of every rubber seal in your engine, you want just the plain old additive.

Alternatively, maybe a couple of squirts of Lucas assembly lubricant (or similar) into the engine after each oil change? That stuff has tons of ZDDP in it for break-in purposes. (This is actually what I did with my last bottle of assembly lube since there was hardly any left)

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[ForcedFirebird]

Just a follow up on this, and another option.
STP makes a very widely and cheaply available product simply called "STP oil treatment", made from a very thick synthetic base stock oil, and ZDDP additive. I've read that it comes in two kinds, a thick 8cyl version and a thinner 4cyl version, but so far I've only ever seen the 8cyl version on the shelves. It's been around since at least the 70s, and a lot of muscle car guys swear by it so it must do SOMETHING. If you decide to try it out, make sure you don't get the kind that designed to stop leaks or whatever because that'll cause damage to the integrity of every rubber seal in your engine, you want just the plain old additive.

Alternatively, maybe a couple of squirts of Lucas assembly lubricant (or similar) into the engine after each oil change? That stuff has tons of ZDDP in it for break-in purposes. (This is actually what I did with my last bottle of assembly lube since there was hardly any left)

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It tends to be more expensive to purchase oil then add zinc vs. just purchasing oil with enough zinc.

[jeffnhiscars]

May as well add my 2c....Another good reason to bench build a head to swap in is that AMC heads do not have a great reputation. FYI rocker faces are case hardened all the way through as opposed to the surface only as on the cam. That makes them a good candidate to reface them for 1/3 of what new (and IMO inferior) rockers cost.

[D.Martijn]

If I go through with the cylinder head refresh I'll probably look into getting an original head with a new camshaft & rockers. Shouldn't be a problem to reuse the original valve if they are still good.