Friday, November 02, 2007

Always double check.

Well, the reason my K series engine had a manky cam lobe may have surfaced during a pre-assembly dummy run of the cam carrier.

Now...the head has the cams sandwiched between the head and cam carrier...I stuck the cam carrier on and just nipped the bolts up and the inlet cam is fine. However the exhaust cam had some excess play, up and down, worse at the back...So the carrier was not fully home for some reason.

I noticed when I pulled it apart that there was a small bit of pick-up marking on the rear journal housing. Nothing to worry about its a small mark. However on very close inspection some of this material that had picked up had made it into the face area on the carrier...Now if it was put together right, torqued down how can this material form a tiny burr on a matting face that is bolted down flat onto another piece of alloy that is also flat? Thats not possible for it form a burr there as it would need to lift the carrier up and move material to the right into a space that doesn't exist...There was no dimple in the head under it so it cannot have moved there. Bit odd.
I removed the burr and its perfect. I also noticed another small piece of machining debris that had ended up crushed somewhere else into the carrier, removed that too. However that was not the source of the loose exhaust cam.

From my assessment of the engine it may have had the head removed for a gasket job in the past. Being as it had only been 30K miles and had a manky crap factory gasket and plastic head dowels I thought it was unlikely, but it was an older 99 engine before some updates to the gasket...I did notice the head looked like it had been sanded on a special machine (factory reface to save skim) I found this out after I stripped it... It now looks like some slaparsed Rover engineer may have stripped the head and stuck it back together long time ago with this piece of debris I mentioned between the head and carrier, causing the exhaust to be very slightly loose, the gloop used would taken up the gap and sealed ok....the inlet cams would not be effected by being loose as they are centralised by the VVC system at either end, so they were ok. I assume its been run for a while with a loose exhaust cam, thats caused some odd harmonic and destroyed the lobes....Also this all adds up as the rear two lobes were not good on the cam and all the followers were not what I'd have expected from a low mileage engine and all the exhausts needed replacing. These K cams are very high quality.

So my diagnosis is that you should NEVER trust a dealer, or main dealer mechanic to do anything bar wreck your car.

Lucky the carrier and head journals have survived and the engine should now by quieter and not self destruct...Had I not done the usual and trial fitted everything and checked everything it would probably eat cams in no time and be noisey and horrible.

Cannot see it left the factory like that, someone else has been involved, warrent job (hohoho). Also its got a mark inside the carrier, someone has added, some numbers, maybe this would tell me the whole story if I knew what it meant.

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