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compressed air system for replacing valve oil seals, etc
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Lanchester 1953



Joined: 05 May 2016
Posts: 34

PostPosted: Thu Jun 16, 2016 1:30 pm    Post subject: compressed air system for replacing valve oil seals, etc Reply with quote

Has anyone used the system for removing valve springs with compressed air to the cylinder and the special spring compressor? I need to replace the valve oil seals on my Lanchester and think this will save time and effort. It was always recommended for Rolls Shadows, Spirits etc.
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peter scott



Joined: 18 Dec 2007
Posts: 6221
Location: Edinburgh

PostPosted: Thu Jun 16, 2016 7:05 pm    Post subject: Reply with quote

I replaced a broken spring by wedging the valve with a shaped tool through the plug hole. I have read of others filling the combustion chamber with rope.

Peter
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MikeEdwards



Joined: 25 May 2011
Posts: 1907
Location: South Cheshire

PostPosted: Fri Jun 17, 2016 10:26 am    Post subject: Reply with quote

I've heard of using rope / string as well, just remember to keep hold of one end.

I'd imagine the problem with using compressed air might be potential damage to oil seals as you pressurise the crank case past the piston rings, though that might vary from engine to engine.
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Lanchester 1953



Joined: 05 May 2016
Posts: 34

PostPosted: Fri Jun 17, 2016 11:15 am    Post subject: Reply with quote

I never heard of the rope before! I think a tool could be made to do the trick, it all depends on the clearance at TDC and relative positions of the spark plug, valves , etc.
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Bitumen Boy



Joined: 26 Jan 2012
Posts: 1420
Location: Above the snow line in old Monmouthshire

PostPosted: Fri Jun 17, 2016 11:16 am    Post subject: Reply with quote

The thing that always worries me about the idea of using compressed air is the possibility of the air supply failing in the middle of the job! If I was doing a job like this I would use rope, IMO it's just the safer option. As an additional precaution I would tie one end to a big washer, socket or something else too big to go down the plug hole...
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Lanchester 1953



Joined: 05 May 2016
Posts: 34

PostPosted: Fri Jun 17, 2016 11:20 am    Post subject: Reply with quote

MikeEdwards wrote:
I've heard of using rope / string as well, just remember to keep hold of one end.

I'd imagine the problem with using compressed air might be potential damage to oil seals as you pressurise the crank case past the piston rings, though that might vary from engine to engine.
So put some thick oil in the cylinder as well. It should only take a few seconds to fit new seals. Also, make sure the crankcase breather is clear, so as to stop any pressure in the crankcase. I only have 4 valves to do.
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Lanchester 1953



Joined: 05 May 2016
Posts: 34

PostPosted: Fri Jun 17, 2016 11:22 am    Post subject: Reply with quote

Bitumen Boy wrote:
The thing that always worries me about the idea of using compressed air is the possibility of the air supply failing in the middle of the job! If I was doing a job like this I would use rope, IMO it's just the safer option. As an additional precaution I would tie one end to a big washer, socket or something else too big to go down the plug hole...
true, but that is why compressors have reservoirs. What sort of rope, anyway? it has to be almost non-compressible.
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47Jag



Joined: 26 Jun 2008
Posts: 1470
Location: Bothwell, Scotland

PostPosted: Fri Jun 17, 2016 11:41 am    Post subject: Reply with quote

In Canada We used the compressed air method a lot in the 60s on the Ford inline sixes. The oil would drip onto the spark plugs and cause the engine to miss. This was when Champion developed the extended nose spark plugs as one of the fixes. Once the compressor has charged the cylinder there isn't a lot of air leakage. If there was then the engine was due a ring job. I can't recall the shape of the valve spring compressor though.

I still have the modified 18mm plug with air connector brazed on in my toolbox Very Happy

Art
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Lanchester 1953



Joined: 05 May 2016
Posts: 34

PostPosted: Tue Jun 21, 2016 9:09 pm    Post subject: Reply with quote

47Jag wrote:
In Canada We used the compressed air method a lot in the 60s on the Ford inline sixes. The oil would drip onto the spark plugs and cause the engine to miss. This was when Champion developed the extended nose spark plugs as one of the fixes. Once the compressor has charged the cylinder there isn't a lot of air leakage. If there was then the engine was due a ring job. I can't recall the shape of the valve spring compressor though.

I still have the modified 18mm plug with air connector brazed on in my toolbox Very Happy

Art
so how exactly do you go about doing this? do the rockers have to be removed? would you remove them then replace the shaft?
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47Jag



Joined: 26 Jun 2008
Posts: 1470
Location: Bothwell, Scotland

PostPosted: Tue Jun 21, 2016 10:01 pm    Post subject: Reply with quote

The rocker shaft has to come off. This then leaves all the valves in the closed position. You will have to make an airline adapter from an old spark plug and a snap on air line connector. Some thought will have to be given as to how you are going to compress the valve springs. A trick I learned to remove the valve springs is to use a 3/4 AF deep socket, place it on the valve collar and give it a smack with a 'knocking stick'. The collets should jump out and the collar is loose to remove it and the spring leaving the valve stem ready to swap/replace the seal. The part that requires thought is how to compress the valve spring enough to get the collets back in. It was back in the late 60s I was doing this sort of job so the memory of how that was done is vague. I seem to recall a device like a two legged bearing puller but with uneven length legs to fit the valve spring. Look at the Snap-on site to get an idea what is required.

http://buy1.snapon.com/catalog/tools.asp?tool=all&SUB_Cat_ID=629550&SUB_Cat_NAME=Valve+Service+Tools&Cat_ID=629055&Cat_NAME=Valve&group_id=675632&group_name=Valve+Spring+Depressors&store=uk


Valve Spring Depressor, Self-Leveling

Item Qty Price**
Valve Spring Depressor, Self-Leveling
Stock#: CG90

43.80
(excl. VAT)
52.56
(incl. VAT)
where applicable
Add To Cart
Checkout

Description:
Self-leveling action compensates for any helix angle spring. Jaw length can be adjusted. Pulls with equal pressure on both jaws.
Product Specifications
Stock #

Art
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47Jag



Joined: 26 Jun 2008
Posts: 1470
Location: Bothwell, Scotland

PostPosted: Tue Jun 21, 2016 10:03 pm    Post subject: Reply with quote

The rocker shaft has to come off. This then leaves all the valves in the closed position. You will have to make an airline adapter from an old spark plug and a snap on air line connector. Some thought will have to be given as to how you are going to compress the valve springs. A trick I learned to remove the valve springs is to use a 3/4 AF deep socket, place it on the valve collar and give it a smack with a 'knocking stick'. The collets should jump out and the collar is loose to remove it and the spring leaving the valve stem ready to swap/replace the seal. The part that requires thought is how to compress the valve spring enough to get the collets back in. It was back in the late 60s I was doing this sort of job so the memory of how that was done is vague. I seem to recall a device like a two legged bearing puller but with uneven length legs to fit the valve spring. Look at the Snap-on site to get an idea what is required.

http://buy1.snapon.com/catalog/tools.asp?tool=all&SUB_Cat_ID=629550&SUB_Cat_NAME=Valve+Service+Tools&Cat_ID=629055&Cat_NAME=Valve&group_id=675632&group_name=Valve+Spring+Depressors&store=uk


Valve Spring Depressor, Self-Leveling

Item Qty Price**
Valve Spring Depressor, Self-Leveling
Stock#: CG90

43.80
(excl. VAT)
52.56
(incl. VAT)
where applicable
Add To Cart
Checkout

Description:
Self-leveling action compensates for any helix angle spring. Jaw length can be adjusted. Pulls with equal pressure on both jaws.
Product Specifications
Stock #

Art
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Peter_L



Joined: 10 Apr 2008
Posts: 2370
Location: New Brunswick. Canada.

PostPosted: Tue Jun 21, 2016 10:14 pm    Post subject: Reply with quote

I have done it in the 60's using the blowing end of a domestic vacuum. The comforting thing was we knew that at TDC the valve would not leave the guide. Disconnected the battery, put it in gear (highest available) and applied handbrake and wheel chocks.

I copied and pasted the following..


1. Remove the valve cover

2. Find the particular cylinder your going to work on

3. Set that cylinder at TDC so you have the smallest volume to keep pressurized

4. Insert your adapter and set your line pressure at around 20-40 psi.

Remember to not go crazy and try to pressurize the cylinder with 120 psi just because your compressor can do it. While I know that the cylinder experiences pressure way higher, there is just no point. Now you are all set up and you can change those leaky valve stem seals in a matter of a couple of hours instead of a days project.





Another trick that works just as well, but requires more finesse and time is to use a rope. Yes you heard me correctly, I said a rope. You want to use the soft wax covered ropes often used for rock climbing. Then do the following:

1. Locate the cylinder you plan to work on

2. Lower the cylinder half way down

3. Feed the rope down into the spark plug hole while giving it a little turning motion with your hand. The idea is to get the rope to coil like a snake and fill the cylinder area.

4. Start to bring the cylinder up until you feel the rope compress against the roof of the combustion chamber.

5. Have a friend hold or wedge something to hold the crank while you compress out the valves. With the nice, soft rope you can compress the valves and remove the valve spring clips out of the retainer without doing damage.
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exbmc



Joined: 18 Jun 2009
Posts: 237
Location: Derby East Midlands

PostPosted: Mon Jun 27, 2016 12:13 pm    Post subject: rope trick Reply with quote

The rope trick, is quite routine in light aviation. Usually, three lengths of about two yards, and 3/8" thick rope, is fed in through the top spark plug hole.
Bring the piston up towards tdc, and try the spring compressor. If there is any give, in the valve, back off the piston, stir up the rope, or add a bit more.
Run the piston up again, until the valve is solid, then remove the collets, springs and cap.
This is usually carried out, when the engine has valve stick intermittently.
So now, the piston is backed away, the rope all removed, and the valve can be pushed in, until you catch it with a flexible grabber. A quick run up the guide with a flex hone, wash out, lubricate and refit the valve.
Then, of course, the rope trick again to put the springs etc back.
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MVPeters



Joined: 28 Aug 2008
Posts: 688
Location: Northern MA, USA

PostPosted: Thu Jun 30, 2016 3:33 am    Post subject: Reply with quote

I just came across Wheeler Dealers, (listed as S13, Ep1 on US TV, but I don't think that's correct). It's an episode about a red '68 Corvette.
Ed China changed the valve stem seals using compressed air & a simple pry-bar spring compressor. As always, he makes it look easy! - but it's worth watching.
Quick research shows that this seems to be a common technique in the US. The pry-bar & plug adapter appear to be readily available here for around $20-$30 a piece - or 15-20GBP (it would have been even less last week!).
I hope this helps.

Edited to add: I think it's episode 8 & may be on UK TV on July 4th.
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