So after finally locating an oil leak which had already caused my heater coolant hose to deteriorate and also leak, I was going to replace the P30 rubber seal at the intake camshaft, distributor side when I noticed that the intake cam lobes were not properly alligned with the rockers. As it turns out, the intake camshaft has visibly moved towards the distributor side of the engine and the cam gear is actually grinding the back cover, which explains a 'bad bearing-like' sound I was hearing sometimes with the engine idling and possibly also a very noticable difference in engine noise when cornering left vs right.

So I set the engine to TDP, completely loosened Cyl. 3 & 4 valve adjustment screws and turning the engine a bit further I managed to free all rockers on the intake side. By pulling the cam gear out and pushing it back in I could feel the camshaft end play being multiple millimeters (service limit is 0,5 mm)

Removing the cam bearing cap that also holds the rubber seal revealed that the camshaft has actually machined itself into the bearing cap as is visible on the pictures. On the last picture, you can see a bearing cap as how it's supposed to look. Now I have a theory of what has been going on here but I would first like to hear your thoughts about the cause and possible solution/repair. One thing I shouldn't forget to mention is that the cam cap seal has probably been leaking for as long as I own the car (93 Prelude) which is 17 years and about 65K kilometers.

 

I have been digging deeper and deeper into this over the past weeks, trying to find an answer. What I found so far is that camshafts usually have two thrust rings that run on each side of a bearing, with the bearing side surfaces being called the 'thrust faces'. This seems to be the case on most overhead cam engines like a Nissan RB26 for example. How this works seems pretty straightforward; the oil gets pressed out of the bearing on both sides, between the thrust faces and thrust rings. Because of this they don't wear.

What I don't understand is why the H22 camshaft has only a single thrust ring that runs against the thrust face of the final bearing. And the ring runs trapped in the groove of the bearing cap but that outer side (side that is grinded in the pictures, side of the rubber seal) does not have a constant oil pressure applied to it because it's not the side of a bearing. It may be running in oil at best.

Is what you can see on those pictures simply the result of what happens to these engines after a while when doing hard cornering on a regular basis (we have a lot of roundabouts here) or am I completely misunderstanding the mechanism of how the camshaft is held into place on these engines? Or anything else?

 

I have seen my fair share of H22 engines over the years... built my first one in 2001. I have never seen cylinder head/camshaft damage like you have pictured above. Incidentally, "B" series and "D" series engines have a similar camshaft retention/location system (the slot for the raised "ring" around one end of the camshaft), and I haven't seen damage like this in any of them either.

In short... they all don't just wear like this over time. It would require pressure against the cam gear end of the shaft to begin to wear the head casting and cam cap... and I can't fathom what would have to occur to cause this damage.

 

Thanks for your reply.

Only thing I can think of is a occasion where the engine overheated pretty badly a while ago, half of the coolant slowly cooked out during continuous high speed driving. The head might have warped slightly, the head gasket also seems to be leaking oil to the outside on the same corner where that damaged cam cap is but I'm not sure if that oil leak was already there before it overheated. Still indeed I can't imagine how that could lead to this damage, like you say there would require to be a force pressing against the cam gear end of the shaft. Can it be a timing belt being too tight? Failing auto tensioner?

Anyway, I decided to continue driving with this for now, looking for a head replacement in the future.

 

What about the possibility of an incorrectly machined cylinder head surface ? If a head casting was cut at an angle from end to end... and cut deeper on the cam gear end... this could put pressure on the cam gear end of the cams as the timing belt walks toward the outside.

 

Hmm seems highly unlikely, I doubt a head like that would ever pass quality control, Honda's quality control was pretty good back in the day I believe.

I have a new theory now. Normally what happens is, a small oil bath is formed at that spot where the camshaft ring runs against the thrust face. This lubricates that spot so that the ring always runs in the oil. The head is contructed in such a way so that oil gets trapped in that spot, it can only flow out when the 'bath' is full, it overflows. This only works obviously if the P30 rubber seal is actually sealing, otherwise the oil wil simply run out from there. So what I think that happened is, every time the car has been sitting, the oil has leaked out and the camshaft ring will run dry against the outer thrust face of the cam cap. Maybe even while driving the bath will never fill up properly or not quick enough. Over many miles and years this way it has grinded itself a few milimeters into there.

Now that I replaced the seal the oil bath should be there again, I was testing the car yesterday and I swear the sound I was hearing while cornering to the left is almost gone, I need to corner really hard to hear it slightly.
Of course this head will still need to be replaced in the future but I hope to have atleast stopped it from wearing further.

Let me know what you think about my theory.