It’s nothing new, cam lobes have been going missing on the 16v turbo engine for a lot of years now, a few different theories have been put forward as to why and i’ll discuss those below. The main point of this article is avoiding it not the first time, but the second or third too.
The first idea put forward as to why, is that of heat from the exhaust manifold soaking through and affecting the oil, maybe heating it excessively, especially when the engine is shut down. The opposition to this theory (if it happens) is as soon as the engine is turned the bucket and lobe are coated with oil and all is well, The 8v engine suffers much less yet the manifold is a similar distance from the head. One thing in favour of this is that when the engine was used in the Fiat Coupe there was a heat shield fitted to the exhaust manifold, although confusingly this wasn’t on it when in the Kappa!
Another idea is poor quality cam material, this is also a good one, probably my equal favourite, but for such a long period of time? Even when the engine was used in the Fiat Coupe 16v turbo the problem was still widespread – maybe the early cars suffered less and the problem got worse as they got further in to production, we don’t see many (any!) 16vt Kappas over here so I don’t know if the problem existed there.
Poor quality oil and extended oil change intervals? Certainly I think this is the main culprit, especially as some oils are low in the very slippery ZDDP since the introduction of the catalytic converter and flat tappet cams like these require a lot of good quality lube. But then comes along something which blows that theory out of the water; we took apart an engine which we knew had been abused by the owner in every way, cheapest oil he could find to top up (when the oil light came on) no oil changes etc. Inside the head it was stained brown, cam condition? Yes you’ve guessed it, they were fine, all lobes present.
Incorrect grade of oil has been suggested, this one I like. Lancia specify 15/40, yet many use 10/40 or 10/60 or even 5/40, 5 is certainly too thin.
The cams on naturally aspirated 16v engines don’t seem to suffer! These engines don’t run as hot as the turbo versions….
Worn valve guides is another one put forward. The valve is supposed to transfer the heat to the valve seat and the guides, when they become worn it can no longer do that so it goes up the stem and into the bucket lifter. The opposition to this would ask why doesn’t it happen to the 8v engine as much? The guides in that engine are often very very worn. Also, I have taken engines apart with worn out cams and the guides haven’t been too bad.
Also consider incorrect valve clearances, now that I can’t comment on because when the lobes are worn the corresponding shims have been battered too.
Oil distribution problem? Vague possibility, but i’ve never seen it in the flesh. Sticking bucket lifters? Never seen that as a problem.
Now add in the fact that the engine has never been thoroughly overhauled and and can be running more power (usually by turning up the boost) therefore creating much more heat and you have all the ingredients for failure.
This is just a brief summary, i’m sure it could be discussed and tested at much greater length, the problem we have is that these engines have been running from 1990 onward so we don’t know the precise history of a lot of them.
I have to say I’m quite liking the poor quality cam material, oil and extended service interval explanation, maybe it is a combination of a few of the above, one engine I saw had knocked out lobe 6 on the exhaust twice in a row, why No.6? It has to be said that this engine did have very worn valve guides, cause or effect? Again, the work was done before I saw it, so I don’t know exactly what went on, it’s probable someone replaced the cam with one which was already on its way out.
Sadly as you can see, no absolutely definite cause and it’s possibly a combination.
But how do you spot it? It comes in varying stages of wear, when it is just starting you need to look for striation, this is a series of lines (like ripples from a stone thrown into a pond) around the high point of the lobe and as it gets worse a small pinprick sized hole can form in the centre. At this point I would be fitting magnets and monitoring the situation carefully, but wouldn’t be unduly worried as i’ve seen these patterns on cams which were running fine. Ultimately and on an engine build you would check each lobe with a micrometer.
The other is to look at the lower recessed band which runs around the edge of the lobe, if that has gone missing then you’ve got serious problems, just as you do if you put your finger over the lobe and feel it for sharpness, if it’s gone pointy it’s game over for that cam.
Either way, this is the important bit you need, but don’t want to know and that is where does all that metal go to which has been worn from the cam lobe? Because it is so fine it doesn’t necessarily get collected by the oil filter, if it does it can block it and during a cold start when the pressure relief valve opens up it can be swept back for another lap around the engine where it grinds down the crank, oil pump, cam shaft journals, the head which it runs in, the valves, the guides and of course the other cam lobes too as well as many other part of the engine. Basically you have fine lapping paste circulating around your engine, this is why when one lobe goes (unnoticed) others follow on afterwards. Look at the wear on the cam journals pictured above ^^.
When it has happened the problem is it’s hiding in places you can’t get to unless a full strip down and clean is done, don’t forget the oil cooler either, it either needs careful cleaning or replacement as it gets caught up in the fins within the matrix, obviously this is a very expensive job. What we have seen is people just replacing cams, maybe an oil and filter change and the problem recurring again and even for a third time, that’s a bitter pill to swallow when you’ve paid for a crap job doing 3 times, it’s quite some way towards doing it properly the first time.
So what to do? Well checking the condition of your cams is a start, but then work through the list of causes and apply a cure.
Heat shield to exhaust manifold.
Good quality fully synthetic oil with ZDDP in it, or an additive containing it and the correct grade. In Summer use a 15/50, in Winter you could use the same or go for a 10/50 or 60. Personally I would recommend Motul 15/50 with a ZDDP additive.
6000 mile/ two year oil changes.
Fit better quality camshafts, the new replacements which are black are made from better material, the cam has been surface hardened, then polished, then hardened again. We fit nitrided steel cams, much harder than cast iron ones of course, but then also more expensive.
We already fit and sell bigger oil filters which have the important higher bypass rate and anti-drain back membranes, but have also recently introduced oil filter magnets to our range, the idea here of course is that they catch the ferrous particles as they get pumped past and hold onto them. Cutting an oil filter open to check if you’ve caught anything is a messy business, If you do cut open an oil filter don’t use a hack saw or angle grinder, the metal particles from that process will of course muddy the results. You can buy oil filter openers, chisel off the the crimped on rim or even put one in a lathe and cut it open using a parting tool.
This article was compiled (and with thanks to) considering some of the opinions of Tanc Barratt and others who I had long conversations with before writing this.