The other problem with compressed air....unless the crank is also locked....that air pressure can push the piston down the bore too... Air just isn't a great methodGDCobra wrote: ↑Mon Apr 12, 2021 11:28 amI agree having something semi-solid in the bore is better than that compressible air.stevieturbo wrote: ↑Sat Apr 10, 2021 9:27 pmCompressed air is good in theory, but the biggest problem is getting the collets unseated, which can often take a little tap on the retainer with a socket/hammer. If you do not have enough air pressure, or when you tap the valve opens and you lose all air pressure....it would be extremely difficult to unseat the collets to allow you to use a tool to remove them.GDCobra wrote: ↑Sat Apr 10, 2021 6:34 pm
May be worth taking the drain plug out of the sump and making sure the rope isn’t coming out of there.
That would indicate a more serious issue!
Seriously though, that’s a god d tip, I’ve heard of a similar practice with compressed air but the rope sounds simpler.
At least with rope, it gives you a solid base against the valve.
I just use thinnish blue nylon rope, have the piston a bit down the bore, shove a lot in, and then rotate so the piston locks up tight against the valves.
It means no matter what happens the valves will never drop anywhere bad. If you lost the air seal for any reason with compressed air, the valve could drop.
I've never done it either way myself so I'm not speaking from experience but if it did use air I think I'd take the piston to TDC or thereabouts so that if a valve did drop it would not go far and presumably still stick out of the guide.
Mind you I guess I'd always be expecting to have to whip the head off anyhow. I'll like the idea of this rope method.
Valve Stem Seals
Moderator: phpBB2 - Administrators
-
- Forum Contributor
- Posts: 3979
- Joined: Sat Nov 18, 2006 6:22 pm
- Location: Northern Ireland
Re: Valve Stem Seals
-
- Helpful or Confused
- Posts: 115
- Joined: Mon Dec 31, 2018 2:29 am
- Location: Thornbury New Zealand
Re: Valve Stem Seals
The piston has to be at bdc ,air pressure will push it there. Even if you can ballance the piston at tdc there is the potential for it to suddenly move to bdc .....can munch fingers . Bit of clean rope would be my choiceGDCobra wrote: ↑Mon Apr 12, 2021 11:28 amI agree having something semi-solid in the bore is better than that compressible air.stevieturbo wrote: ↑Sat Apr 10, 2021 9:27 pmCompressed air is good in theory, but the biggest problem is getting the collets unseated, which can often take a little tap on the retainer with a socket/hammer. If you do not have enough air pressure, or when you tap the valve opens and you lose all air pressure....it would be extremely difficult to unseat the collets to allow you to use a tool to remove them.GDCobra wrote: ↑Sat Apr 10, 2021 6:34 pm
May be worth taking the drain plug out of the sump and making sure the rope isn’t coming out of there.
That would indicate a more serious issue!
Seriously though, that’s a god d tip, I’ve heard of a similar practice with compressed air but the rope sounds simpler.
At least with rope, it gives you a solid base against the valve.
I just use thinnish blue nylon rope, have the piston a bit down the bore, shove a lot in, and then rotate so the piston locks up tight against the valves.
It means no matter what happens the valves will never drop anywhere bad. If you lost the air seal for any reason with compressed air, the valve could drop.
I've never done it either way myself so I'm not speaking from experience but if it did use air I think I'd take the piston to TDC or thereabouts so that if a valve did drop it would not go far and presumably still stick out of the guide.
Mind you I guess I'd always be expecting to have to whip the head off anyhow. I'll like the idea of this rope method.
I wish I was young again , Id be heaps smarter than the first time
Re: Valve Stem Seals
Really? I wouldn't have thought it was beyond the wit of man to be able to keep the engine in whatever position you wanted. It would be crazy to try and do this with engine at BDC for the reasons Stevieturbo mentioned, very good chance of dropping a valve, all in all the rope trick seems a better way to go.Mc Tool wrote: ↑Thu Apr 15, 2021 10:22 pmThe piston has to be at bdc ,air pressure will push it there. Even if you can ballance the piston at tdc there is the potential for it to suddenly move to bdc .....can munch fingers . Bit of clean rope would be my choiceGDCobra wrote: ↑Mon Apr 12, 2021 11:28 amI agree having something semi-solid in the bore is better than that compressible air.stevieturbo wrote: ↑Sat Apr 10, 2021 9:27 pm
Compressed air is good in theory, but the biggest problem is getting the collets unseated, which can often take a little tap on the retainer with a socket/hammer. If you do not have enough air pressure, or when you tap the valve opens and you lose all air pressure....it would be extremely difficult to unseat the collets to allow you to use a tool to remove them.
At least with rope, it gives you a solid base against the valve.
I just use thinnish blue nylon rope, have the piston a bit down the bore, shove a lot in, and then rotate so the piston locks up tight against the valves.
It means no matter what happens the valves will never drop anywhere bad. If you lost the air seal for any reason with compressed air, the valve could drop.
I've never done it either way myself so I'm not speaking from experience but if it did use air I think I'd take the piston to TDC or thereabouts so that if a valve did drop it would not go far and presumably still stick out of the guide.
Mind you I guess I'd always be expecting to have to whip the head off anyhow. I'll like the idea of this rope method.
-
- Forum Contributor
- Posts: 3979
- Joined: Sat Nov 18, 2006 6:22 pm
- Location: Northern Ireland
Re: Valve Stem Seals
At BDC, one of the valves will be open, BDC is not an option. ( although I guess you would have rocker gear removed so would be an option...just a dangerous one. )
-
- Top Dog
- Posts: 1278
- Joined: Mon May 04, 2009 6:53 am
Re: Valve Stem Seals
I've used the rope trick and it worked nicely for me.
It must be a soft, pliable rope to be able to fold up on itself as you turn the crankshaft, and I used a power bar that I tied off onto a hard point to prevent it moving as a belt and braces thing.
It must be a soft, pliable rope to be able to fold up on itself as you turn the crankshaft, and I used a power bar that I tied off onto a hard point to prevent it moving as a belt and braces thing.
Cheers,
John
John
-
- Helpful or Confused
- Posts: 115
- Joined: Mon Dec 31, 2018 2:29 am
- Location: Thornbury New Zealand
Re: Valve Stem Seals
Surely you would have to remove rocker gear to remove the spring and retainer to replace the stem seal .stevieturbo wrote: ↑Fri Apr 16, 2021 5:26 pmAt BDC, one of the valves will be open, BDC is not an option. ( although I guess you would have rocker gear removed so would be an option...just a dangerous one. )
Piston at bdc with the air line in the plug hole , now I aint going to bother figuring out the surface area of a valve head so lets call it 1 square inch (its bigger ), times that by 100psi = you need to put better than 100 pounds force on the end of the stem to pop the valve open ........it aint goin nowhere. .
I dont understand how it could be dangerous .....
Piston cant go further down than bdc , engine effectively locked up , nothing going to move. I have used this method of holding vavles in place when re-shimming my Ducati motorbike engines for years , never had one drop , I did , however manage to drop a closing shim retainer down the oil return hole ,they get plugged with a blob of grease now
I wish I was young again , Id be heaps smarter than the first time
-
- Forum Contributor
- Posts: 3979
- Joined: Sat Nov 18, 2006 6:22 pm
- Location: Northern Ireland
Re: Valve Stem Seals
Mc Tool wrote: ↑Sun Apr 25, 2021 7:04 amSurely you would have to remove rocker gear to remove the spring and retainer to replace the stem seal .stevieturbo wrote: ↑Fri Apr 16, 2021 5:26 pmAt BDC, one of the valves will be open, BDC is not an option. ( although I guess you would have rocker gear removed so would be an option...just a dangerous one. )
Piston at bdc with the air line in the plug hole , now I aint going to bother figuring out the surface area of a valve head so lets call it 1 square inch (its bigger ), times that by 100psi = you need to put better than 100 pounds force on the end of the stem to pop the valve open ........it aint goin nowhere. .
I dont understand how it could be dangerous .....
Piston cant go further down than bdc , engine effectively locked up , nothing going to move. I have used this method of holding vavles in place when re-shimming my Ducati motorbike engines for years , never had one drop , I did , however manage to drop a closing shim retainer down the oil return hole ,they get plugged with a blob of grease now
Because sometimes it can take good effort to unseat the collets, and air pressure often will not allow that. And it is dangerous as with the piston down the bore, if it does drop....it will drop down wayyyy too far to make your day end well.
Pretty simple stuff.
-
- Helpful or Confused
- Posts: 115
- Joined: Mon Dec 31, 2018 2:29 am
- Location: Thornbury New Zealand
Re: Valve Stem Seals
Oh sorry ,Here was me thinking that dangerous meant there was some significant risk of injury, having a valve drop isn't dangerous, a massive pain in the arse I spose ,wouldnt know for sure as its never happened to me . Dunno what sort spring compressor you use but mine has a screw thing that winds the retainer down off the collets ( conventional engine valves , Ducati doesnt has valve springs ). I have seen a home made spring remover for the rover , just a flat bit of steel bar about 40mm wide ,8mm thick and 300mm long , has a 10mm hole in one end and a 20mm hole about an inch further up the bar . Idea is rocker shaft bolt goes thru small hole and screwed into head in its normal place , large hole is positioned over valve retainer ( if your going to make one distance between holes is sorta measured by eye , 10mm hole can be slotted a bit for fit ) , press down and valve stem and collets come up thru 20mm hole . For what its worth almost all of the engines I have replaced worn guide seals( as opposed to seals that have just gone hard and cracked ) on also had significant wear in the guides, allowing the valve stem a bit of wiggle and I think that maybe its this wiggle that wears the seal .
I wish I was young again , Id be heaps smarter than the first time
-
- Top Dog
- Posts: 1278
- Joined: Mon May 04, 2009 6:53 am
Re: Valve Stem Seals
Put a socket that is a bit smaller than the diameter of the retainer over the retainer and thump it with a rubber mallet to unstick the collets. It should also release the collets, but you may need to hit it a few times for both. Works well and is an easy fix.stevieturbo wrote: ↑Sun Apr 25, 2021 10:28 amBecause sometimes it can take good effort to unseat the collets, and air pressure often will not allow that. And it is dangerous as with the piston down the bore, if it does drop....it will drop down wayyyy too far to make your day end well.
Pretty simple stuff.
Cheers,
John
John
-
- Forum Contributor
- Posts: 3979
- Joined: Sat Nov 18, 2006 6:22 pm
- Location: Northern Ireland
Re: Valve Stem Seals
Works great with rope in the chamber...doesn't do so much with air as it will just click the valve open when using air.unstable load wrote: ↑Thu Apr 29, 2021 8:59 amPut a socket that is a bit smaller than the diameter of the retainer over the retainer and thump it with a rubber mallet to unstick the collets. It should also release the collets, but you may need to hit it a few times for both. Works well and is an easy fix.stevieturbo wrote: ↑Sun Apr 25, 2021 10:28 amBecause sometimes it can take good effort to unseat the collets, and air pressure often will not allow that. And it is dangerous as with the piston down the bore, if it does drop....it will drop down wayyyy too far to make your day end well.
Pretty simple stuff.
-
- Top Dog
- Posts: 1278
- Joined: Mon May 04, 2009 6:53 am
Re: Valve Stem Seals
What I meant was to use the thump to unstick the collets from their rest position and then use your tool of choice to remove the bits.stevieturbo wrote: ↑Thu Apr 29, 2021 6:11 pmWorks great with rope in the chamber...doesn't do so much with air as it will just click the valve open when using air.unstable load wrote: ↑Thu Apr 29, 2021 8:59 amPut a socket that is a bit smaller than the diameter of the retainer over the retainer and thump it with a rubber mallet to unstick the collets. It should also release the collets, but you may need to hit it a few times for both. Works well and is an easy fix.stevieturbo wrote: ↑Sun Apr 25, 2021 10:28 amBecause sometimes it can take good effort to unseat the collets, and air pressure often will not allow that. And it is dangerous as with the piston down the bore, if it does drop....it will drop down wayyyy too far to make your day end well.
Pretty simple stuff.
I have got lucky in the past where a set of collets has come off easily with the thump, but the rope in the cylinder is still my go-to method.
Cheers,
John
John
-
- Helpful or Confused
- Posts: 115
- Joined: Mon Dec 31, 2018 2:29 am
- Location: Thornbury New Zealand
Re: Valve Stem Seals
Even if you can bump the collets off with the hammer and socket ( and who hasnt ) you still need one of them spring compressors to reassemble
I wish I was young again , Id be heaps smarter than the first time