how to change valve stem seals without lifting the head

rage

rage

Lifer
hi guys,

A while ago i've replaced my valve stem seals as the engine was out of the car and stripped down anyway. but the car started smoking again when i lt go of throttle, brake using the engine and then picked up on the throttle again a nice puff of blue smoke appeared in my rear view mirror.

so the words "oh no.. not again" popped into mind.
took off the manifold and checked the exhaust ports and there it was.. again.. a nice black oil stain from the valve stem. so one of the seals is leaking..

i really don't want to take apart the whole engine again just to replace one tiny lil bastard of a stem seal. so i was wondering if there are any tricks to switch the stem seal without taking off the head.
 
S

Skalabala

Member +
If its only one then its easy I suppose.
What I do is, fill the cylinder up with soft rope while piston is not tdc and then turn it until it stops.
The valves will then stay closed.
The other way is. Take a spark plug and make it hollow and then screw it into the head and connect a good air supply to it.
This will also lock the valves closed. :)
 
G

GP82

Member +
You need to get a valve spring compressor tool or something that can compress the valve springs with the head on. Once you find a way of doing this then it is jus' a matter of bringing the piston of the cylinder you are working on to the top then use the old rope trick into spark plug hole so you are able to pull the valve back up so not to let it drop into the piston/cylinder.

Once you rig this up, compress the spring, release the collets/keeper's and the retainer, pull the spring out then will get access to the seal. It is a mission, requires alot of patience, but easily done. Good luck!
 
dark_knight

dark_knight

Member +
Skalabala said:
The other way is. Take a spark plug and make it hollow and then screw it into the head and connect a good air supply to it.
This will also lock the valves closed. :)
Click to expand...
why not just plumb the air supply onto the plug silo, or is it that they aren't air-tight with the block..?
& while still on the topic, does anyone have a picture of the valve compressor spring..? i need to make a custom one since none of the machine/tool shops around seems to have any.. :/
 
S

Skalabala

Member +
It wont be hard to make your own spring compressor :)
4E springs can be pushed in with your thumbs so the springs are not that tight.
Make a lever that hooks under the other camshaft with something on to compress the spring.
I have in the past used normal tools like a spanner and screw driver to get it done, but this will not work with a 4E.
 
dark_knight

dark_knight

Member +
Skalabala, you know a picture is worth more words than you can speak.. :D
plus, are you saying that i can't go at it with a spanner and screwdriver if i had helping hands..?
 
dac69er

dac69er

Super Moderator
if the seals have gone again, chances are your guides are worn. you will end up changing the seals again and again until you get that done.

i got my guides replaced when i rebuilt my engine as the exhaust side ones were worn.
 
rage

rage

Lifer
i'm concidering not replacing them as i'm going to start my 5e project this winter. might just let it smoke a bit for a few more months.

the rope trick is a nice one, will remember that one :)
 
dac69er

dac69er

Super Moderator
rage said:
i'm concidering not replacing them as i'm going to start my 5e project this winter. might just let it smoke a bit for a few more months.

the rope trick is a nice one, will remember that one :)
Click to expand...

i would leave it. you drop 1 valve and the head has to come off anyway. just put up with the smoke and get the guides replaced when you have the head off for the 5e build. its nor for long!
 
rage

rage

Lifer
building a completely fresh engine and keeping this engine as a spare. everything will be checked, rechecked and checked again before the new build is done

might do a rebuild on this engine when it's out, just to keep a fresh well running engine as a spare
 
5e colin

5e colin

Member +
rev i have always pushed the valveguids right the way down is that wrong ?? i see u leave a small gap i have had no smokers yet
 
R

Rev

Member +
Not exactly sure which gap you are referring to I have read when the valve is fully open, the gap between the top of the valve stem seal and the bottom of the spring retainer should exceed 1,0 mm .For the valve stem the gap principles are so oil thickness is metered out to control wear etc as mentioned below tighter tolerances are ok. Plus the Starlet I thought uses the injectors spray pattern on the back of the valves to help cooling.

Engine Valve Failure - http://www.aa1car.com/library/ar1192.htm
'Many newer engines with aluminum heads have powdered metal valve guides. The guides are iron based and contain graphite so the guides are not as dependent on oil for lubrication as before. This allows tighter clearances while reducing the danger of scuffing. These guides tend to be brittle and should be pressed in rather than driven in.'
 
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5e colin

5e colin

Member +
wow sorry i meant the valve guide seals ( not the actual guides ) in your link it wasnt pushed right down there was like room for the hook to go underneath
 
R

Rev

Member +
Gotcha now. The valve guide seal should go over the top of the valve guide that is projecting and so it is the side sealing that does the main work. The gap in the photo from underneath the seal is not sealing the oil between the valve guide tube and the valve. These seals are small type so pushing them all the way down I think has merit to maximize the contact area holding the seal.
The only thing is the old seal in the photo shows the brittleness at the bottom in fact the inner coating has fallen off due to heat, if the air gap substantially reduces heat conducting to the top of the seal maybe a slight wear advantage for this type of seal but needs further investigation.
 
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