When finished back the piston off and pull the rope out.
Never failed.
This weekend I'm going to be doing all the valve stem seals on my 40v audi with the heads still on. As I understand I have two options here:
1. Put an airline in the sparkplug hole and use the air pressure to hold the valve in place. If for any reason the air pressure doesn't hold it
well enough it falls into the cylinder and makes the whole job pointless. Audi actually reccomend this method but I'm not so sure...
2. Put the piston at TDC and let the valve fall a few mm - will be more difficult to get the springs back on but can't lose it in the
cylinder.
Don't think I can do both methods together because if I have enough pressure to hold the valve it will probably push the piston back to bdc
anyway. Could maybe put the car in gear though to stop this happening.
I have done this a few times by setting the piston about 25mm before TDC on the compression stroke, feeding 6mm diameter soft rope into the cylinder
to fill the void, then slowly turn the crank to compress the rope against the valves.
When finished back the piston off and pull the rope out. Never failed.
I've used the compressed air method dozens of times, unless you have a low capacity or unreliable compressor the only way it can fail is if you
have a badly leaking valve seat in which case head needs to come off anyway.
I like the ingenuity of the "rope trick" tho'! 
quote:
Originally posted by russbost
I've used the compressed air method dozens of times, unless you have a low capacity or unreliable compressor the only way it can fail is if you have a badly leaking valve seat in which case head needs to come off anyway.
I like the ingenuity of the "rope trick" tho'!
quote:
Originally posted by luke2152
quote:
Originally posted by russbost
I've used the compressed air method dozens of times, unless you have a low capacity or unreliable compressor the only way it can fail is if you have a badly leaking valve seat in which case head needs to come off anyway.
I like the ingenuity of the "rope trick" tho'!
Well it is a cheap little compressor seems to work alright though. I could use the air system at work but then I'd have to work outside.
I like the rope idea but how fiddly is it feeding that rope X 8 cylinders
I use a combo of 1+2 (though haven't done one in a while).
TDC/in gear/handbrake on; That way the pressure won't push the piston down. Then once the spring is off, double check the crank hasn't moved
and I disconnect the air... mainly because the constant hissing will does my head in. Once the seal is on, pull the valve up (few mm) and reconnect
the air while you put the spring/cap/collets on.
I have had the pressure push the piston down once when I first did one, as it wasn't in gear. Very annoying to watch the valve drop. Luckily it
stood on the piston and amazingly stayed in line and came back up when I turned the crank 
I bought lottery tickets that night.
I have a ready made spark plug with a baynet fitting all made up for this job,
and also have done it a couple of times,
150 psi on a typical car engine valve produces a lot of force, you'd have to really pretty hard to break the seal.
Rope trick works for me, done it a few times and there's very little/nothing that can go wrong 
Ian
every time I've done this I've taken the head off and found the valves needed reground anyway and that makes well worth the effort. The last time I found a broken head bolt too!
quote:
Originally posted by Oddified
Rope trick works for me, done it a few times and there's very little/nothing that can go wrong
Ian
quote:
Originally posted by adithorp
quote:
Originally posted by Oddified
Rope trick works for me, done it a few times and there's very little/nothing that can go wrong
Ian
I know a guy who swore by the rope trick, untill one day it tied a knot in itself and wouldn't come back out.
I've done a fair few sets of valve stem oil seals using compressed air without any issues on various types of engines . As said bring the piston to TDC on the compression stroke , put into top gear and pull the handbrake on . Have never tried using rope . I have a Sykes Pickavant kit which helps.
quote:
Originally posted by Oddified
quote:
Originally posted by adithorp
quote:
Originally posted by Oddified
Rope trick works for me, done it a few times and there's very little/nothing that can go wrong
Ian
I know a guy who swore by the rope trick, untill one day it tied a knot in itself and wouldn't come back out.
lol...that would be a bit of $hit luck!.
Ian
I was there at the time and he was showing off... "and then you just pull it out like this... err, shit!" His face was a picture and then when he realise that all his tugging was just tightening the knot.... PMSL