Changing valve seals - rope trick

[dern]

Has anyone used the rope trick for changing valve stem seals in order to avoid removing the head?

Any experiences or advice?

Thanks,

Mark

[dern]

eliot said:

I would try the compressed air trick; Set the piston at TDC for that pot, Cut an old spark plug up, drill hole through middle, weld an air fitting to it and plug into air compressor.

I don't have a compressor and the thing that worries me about this approach is that if I accidentally push the valve down a little the seal will be broken and the valve will drop and then I'll have to take the head off.

Mark

[dern]

stevieturbo said:

String or air both work fine... But Ive tried air in the past, and the air can actually turn the engine over, so best to have it in gear also, or lock the crank from rotating. If the valve did drop, the seal would be broken, but if the piston is at tdc, it cant draop far anyway. String, or thin rope is virtually foolproof.

Thanks Stevie. I know this is a daft question but do I need special string/rope so that I don't leave fibres in the bores or does it really not matter?

Cheers,

Mark

>> Edited by dern on Tuesday 15th February 18:32

[dern]

justin s said:

Aaah,got you thinking after Sunday,Mark.

Indeed. It saves me taking the exhaust manifold off and saves me 60 quid on a gasket set

[dern]

paolow said:

so - in sum, take your pick, but both work a treat! best thing you can do though, before you start, by the cam with a handle thing to squish the valve spring as it may be harder to drive to the shops to get one with your engine in bits

Cheers. I'm not entirely sure what you meant by the handle thing. I've read of methods where you compress the spring without removing the cam using something that pushes down on the spring levering against the cam... is that what you mean?

Mark

[dern]

paolow said:

sorry - drunkeness got in the way of a reasoned post. the piece of kit you are looking for is a handle on the end of a large cam with a couple of teeth on the end. you hook the teeth under the camshaft (using it as your fulcrum against the valve spring) and then lean on it. by doing so you compress the valve spring and, with a cylinder full of rope, you can then remove the colletts, release theh spring and change the stem seal safe in the knowledge that the valve wont fall in . i must confess ive not done it myself - i tend to go down the 'all or nothing' rebuild route, but i know mechanics that do it a lot and with practice - it can be done surprisingly quickly.

Cheers, I think I see what you mean. I'll take the rocker cover off and have a look at what's needed and try and make the tool you're describing.

Thanks,

Mark

[dern]

Did it in the end with one of these...

www.justoffbase.co.uk/s.nl/sc.9/category.213/it.A/id.7467/.f

On the 944 8v the cam box comes off in one assembly so once that was off I was left with 8 springs. The above tool made compressing the springs easy. I used 6mm braided polypropolene rope and fed it through the spark plugs pushing it in with a bit of coat hanger with the piston down about half inch from top. I then moved the piston up until I felt resistance and compressed the spring. At that point you can see if the valve is going to fall by pushing it before you commit to removing the keeper and then the spring.

Regards,

Mark