Cylinder Head Nuts

[myoldjalopy]

I have to remove the cylinder head as its blown the gasket, I think between 1 and 2 cylinders. However, not having done this before, I'm a bit confused as to the order of untightening the nuts. I get the sequential untightening of the five external nuts and the four on the manifold side. But what about the four which hold the rocker shaft to the cylinder head? Are they loosened and removed after the nine nuts that attach the head to the engine block or at the same time as the four nuts nearest the manifold?
Pete

[amgrave]

The 4 nuts on the rocker shaft are for the shaft only, they don't hold the head down so no need to remove them for changing the head gasket. However if you do remove them it is best to undo them a quarter of a turn at a time each until loose but you only need to do this if the head is still on the block, if removed from the block just undo them.

[bmcecosse]

ALWAYS loosen the 4 rocker shaft retaining nuts before touching the head nuts - otherwise they are left holding the forces from the valve springs on valves that are open. More of a possible problem with high lift cams and stupidly high force springs that some fit - but still worth doing anyway. And of course - tighten them last, after the head nuts on re-assembly. Only 25 ft lbf though!

[oliver90owner]

As i see it, removing the rocker shaft simply allows the push rods to be removed and placed neatly in order before removing the head. Still choice of order of operations. An alternative would be to slacken off the adjusters but I doubt many mechanics do that. It needs to be loosened, at least, on head replacement anyway (unless all valve adjusters are loosened).

There is often more than one way to 'skin a cat' as they used to say.

[myoldjalopy]

Indeed there is! In the end I slackened off the four rocker nuts gradually in tandem with the nearest head nuts (i.e. manifold side) as I went through the cylinder head nut sequence. Head is off now and there was a blow between 1 and 2, as I suspected.
If you look at the picture you can see the blow in the gasket. But one of the little holes (bottom right) is blocked with crud.[frame][/frame]
You can also see in the next pic that a hole further back (near the stud, bottom right) has some kind of jelly in it. I suppose they should be cleaned out...with a pipecleaner?? Please advise.[frame][/frame]
And on the underside of the head you can see a burn mark between the first two cylinders, but it doesn't appear to have scored the metal by feeling it. Any thoughts on whether this should be skimmed or just cleaned up? Its obviously a bit dirty. Anything else I should do while the head is off? Just for info, the engine was rebuilt about 10 years ago and has done just over 31,000 miles since then. Was running like a dream before it blew and started making a horrible rattling noise. [frame][/frame]

[bmcecosse]

Obviously you need to clean the head carefully - do NOT rub at it with emery paper or anything like that. It's hard to say from these pics if the head or block have been damaged by the blown gasket. It is very important to stop immediately when a gasket blows - and NOT to struggle on. I would remove all the head studs and then clean block and head carefully with a sharp blade/scraper. Then 'survey' the surfaces with a straight edge (12" steel rule) to see if there are any depressions. As a matter of course the valves should be popped out and ground in. And you can assess the wear on the valve guides and make decisions on them at the same time. This is where a spare head is handy - just swap it on (assuming the block is not scoured) and then work up the old head in your own time.

[MrIan]

I might be wrong but aren't those water passages that are blocked/restricted ? If so that would have incresed the heat on the 1 and 2 cylinders and maybe helped the gasket on it's way?

[bmcecosse]

Unlikely to be a problem on a standard engine - but certainly poke them all clear when rebuilding - and then do a good engine flush once you have it running.

[myoldjalopy]

Ok thank you for your thoughts. I will progress with the cleaning up process.Three questions:

How do you remove the studs and replace them? (One came out with the nut attached - so how do you remove the nut and screw the stud back in?)

Do I just poke some wire (or a pipe cleaner) down the holes to clear them?

And how do you do an 'engine flush?

Thanks,

Pete

[bmcecosse]

Put two nuts on the stud - tighten them together -then unscrew the stud using the lower nut. Just grip the stud in some way without damaging it - and unscrew the nut! Fill with water - run it till hot - drain it. Maybe repeat. You can of course buy fancy flushing chemicals - but a good change of water should do it. Top tip - DO NOT ever attempt to use the radiator drain tap/plug. Just take the bottom hose off.

[myoldjalopy]

OK thanks Roy. I have quite a bit to get on with now! Yes, I have always used the bottom hose to drain the rad - the tap is completely fossilised!

[myoldjalopy]

OK, I have now removed the studs, cleaned up the face of the block and replaced the studs. What I thought were blocked holes were, in fact, not holes at all, but just blanked off with some gunk sitting on top.

Next question - I haven't done anything to clean up the tops of the pistons, so should I and, if so, how? See pics:[frame][/frame][frame][/frame]

[panky]

A green Scotchbright pad and paraffin usually works

[les]

Once upon a time a ring of carbon was left on top of a piston, it was said to soak up any oil. I've never really understood the thinking behind this practice. Maybe in the days when running a clapped out engine was normal!

[myoldjalopy]

I think the idea was that a ring around the piston crown and the top of the cylinder bore formed an oil seal if the piston rings and bores were a bit worn. However, there isn't enough carbon around the edges of my pistons to even create a continuous ring - most of it is in the centre. Possibly no. 2 piston might be possible...........So I suppose I might as well clean it off?

[les]

Yes, clean them all up.

[bmcecosse]

NO -leave them alone !!! You only risk pushing grit down the bores/rings - and it's doing no harm where it is. Just the head to do now -and grind in the valves. Block looks ok from these pictures. Get a decent 'copper' head gasket - and lightly grease it both sides when fitting.

[myoldjalopy]

Urggh! That's two totally contradictory responses! OK, I will have a think about that.........in the meantime - copper gasket.....copper face up?

[MrIan]

I clean my piston tops by masking the rest of the block face off, pack grease into the piston to bore gap, clean piston, then as you lower it a little the grease will in theory have held any rogue bits of muck, clean then lower the piston a little more etc etc.
Might not be an approved method but i've not had any trouble with it.
Thoughts ?

[bmcecosse]

Seriously - the usual advice is to leave well alone. But suit yourself - i've pointed out the possible risks - and all that masking etc...... For no advantage. Copper both sides if you can find it - otherwise as you say copper up against the hotter head face.