owain
Post #1
So, as I know nothing about engines I decided to buy up a spare cylinder head in an attempt to figure out what's what without sacraficing my current engine. However due to the nature of being clueless, I have some questions. The head was in an unknown condition, bought as a replacement but never fitted. The previous owner didn't think it had been skimmed, and clearly hasn't been recently. Whether or not it has been previously, we'll come to shortly.
First up, I dismantled everything that I could. It had been locked using the standard drill bits, so carefully removed those. I was surprised to find the camshafts didn't exactly spin freely (and no, I wasn't knocking the valve heads into each other, I was being very careful), but were extremely stiff. Whether that's just how they are, or because it doesn't have oil in it I don't know, perhaps someone can Craig David Fill Me In on that one. Anyway, all these bits came off pretty easily, bar one previously chewed up bolt through those fings wot hold the cams down.
Being very careful to keep it all in the right order, of course. Spent a while trying to figure out how the tappets come out, only to find you just need to pull them.
Face + palm moment there.
From what I understand, the hydraulic tappets on these engines fill up from oil underneath when the cam is "up" to make sure it's in constant contact with the cam when it comes "down", is that right? In which case, do they need to be refilled with oil somehow when putting it back together again? Or will the oil pump just do its work?
One of the cylinders looks like it's had some water in it to me:
Nothing monumental, I've seen far worse. Nothing that can't be fixed with a skim and a new gasket, I assume? I'm not massively fussed if it turns out this head is no good, it was more a learning exercise than anything. Would be nice if it worked though.
The valves in the leaky cylinder did have a ring of crud around them, but it cleaned off nicely with no proper damage to them.
Do the little collet things need to stay matched to the correct valve? Or is that too anal?
Cleaned it up with some Gunk, then a quick pressure wash to clean it all out:
Before drying it out with a hot air gun, doesn't look too bad to me.
Can anything else come out of this? I can see the green plastic looking bits where the valves go, are them the valve stem seals I've heard of? Do they need replacing or anything? Also, the valve guides themselves - they look pretty well stuck in, I assume that's an engineer's job to get those out?
Spark plugs look okay to me, not that I'd re-use them for the sake of a tenner.
Get the essentials ready...
Greasy valves:
Clean valves:
I've just degreased them for now, but I saw a thing on t'internet that said it was okay to stick them lightly in a drill and use some wet & dry to clean up the faces of them - does that sound okay? I appreciate you don't want to do the seats until you come to lap them in, but the faces should be okay? I don't really know how much you could do before it started affecting compression.
All looks pretty clean, certainly not been recently skimmed though:
Can't really get rid of the water marks at the other end though, leave this for the skimming?
I did have a quick go at lapping in one of the valves in the "leaky" cylinder and it came up really nicely, there's no deep rust or pitting around it at all.
I'm pretty sure three of the valves are bent, they needed a punch and hammer to remove them (which isn't a great sign) and it's not the guides - a different valve will slot in just fine. I've got a micrometer thing I'll use to measure them up accurately some other time, but those three do seem knackered to me. Is that the kind of thing that'd cause an engine to tap?
Also (and this is probably wishful thinking here), say I replace any bent valves, assemble everything back up carefully oiling (every part? Some parts? Any parts to not oil?) as I go, does that mean it shouldn't tap? Or is there someone I could have missed, something only a trained eye would notice?
I know people do say these tap because they weren't rebuilt properly, but I don't know whether that means "by someone who rushed it and didn't care that valves were bent" or whether that means "by an ignorant fool like you, muppet!".
Also, you might notice from the above pictures that two of the valves are different to the others, they have a different sized pocket. Does that mean at some point they will have gone and the head has probably been skimmed already? I have a feeling (but would need to check) that the new valves might be from the leaky cylinder.
Any opinions, answers, expertise or advice would be most welcome, hopefully it'll help someone else out in the future as well.
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Posted 12th Jul 2011 at 02:35
