8v Stem Seal replacement- head on.

[Peter Jones]

Picked up a S/H 1800 motor to go into a MK 1 for a friend.

According to previous owner motor went OK but smoked on startup, a classic stem seal issue.

Before the motor goes in the car I thought I'd replace the stem seals while the motor was still on the stand. There may well be other work that's needed but just doing the seals should see this car through a RWC.

Decided against pulling the head off at this stage, just another potential can of worms that I'd rather not get into for a love job.

Once it's in the car and running again I'll do some compression tests if I'm feeling brave.

I thought that many of you may have heard of Valve stem seals and the issues that arise when they wear out, but not really seen the process of replacing them.

This is the process to replace valve stem seals without removing the cylinder head. I deally Valve stems seals would be replaced as part of a full reconditioning of the cylinder head.

Assuming that you've figured out how to remove the rocker cover and camshaft. (I know that's a lot to assume but that bit is pretty straight forward.)

Here's what you're faced with after removing the cam follower.

Cam followers should be put back onto the same valve they came from.
Hydraulic followers could be replaced about now and solid followers could be adjusted when the cam is re-assembled at the end.



This is the tool used to press down on the valve spring to release the collets that lock into the spring retainer. Sometimes a bump from a hammer helps here if the collets have grabbed the retainer.



To stop the valves from dropping into the cylinder and just moving with the spring compressor, compressed air is used to pressurise the cylinder through the spark plug or diesel injector hole depending on the type of motor. This air valve hold came with the spring compressor kit.



Here the collet is being removed from the depressed spring retainer with the aid of magnet on a stick. (technical ain't it?)



Collets removed.



Springs and retainers out.
The stem seals live down the bottom of a deep hole and must be fished out using valve stem seal pliers which are specially designed for the task.



Here's a comparison of a brand new seal vs the ones that came out.

[Peter Jones]

One with one without seal.



Stem seals come with an installation aid to prevent damage to the seal as they're slid over the valve stem. (The blue thing!)

A little bit of light machine oil (or engine oil) on the seal helps it slide into place too.





The seal is pressed home ideally using a special tool but in this case I've used a 1/4" socket of just the right internal diameter to slip over the seal and drive it home by pressing on the seals metal collar. A couple of very light taps from a small hammer and you can tell it's home when you hear the hammer blow sound like you're tapping on metal.



Spring and retainer back in, collet going back into place



Let the spring back up.





All tools available on e-bay




Pete

[Oneofthegreats]

Awesome write up Pete as usual

A - Grade!

Another thing to add is most of the time with these cyl. heads, the valve stem seals were out due to valve guide wear too.


Another ol-skool trick if you don't have a air compressor or fittings etc is wind the engine down to BDC.
Remove the spark plug
Feed some ( a fair amount) twine etc into the spark plug hole obviously leaving a length hanging out so you don't have to fish the twine out through the spark plug hole!
Then carefully & slowly wind the engine upto TDC in a clockwise direction till it stops/jams

This is another way to hold the valves shut while removing the springs & not having the valves drop onto the pistons

[Peter Jones]

Thanks Tim,

Yeah I should have pointed out that replacing stem seals is usually only a stop gap effort as by the time they're worn out chances are the rest of the motor is too.

I did check the guides by releasing the air pressure and wobbling them about, to be honest I wasn't too impressed with a couple of them but it's for a friend, going into a weekend car with a tight budget on the RWC. It'll see her through for probably a couple of years the way it is.

Bit of an odd motor this one too, first solid lifter 1800 I've seen it's ex pommy import Mk1 carby cabrio.

That's a neat trick with the string, I've seen a few air holds made by smashing the top off a spark and brazing an air fitting to it too.

Pete

[Oneofthegreats]

Your right about the band aid fix though. But to put both your's & her mind at ease

I replaced the valve stem seals only in my current stock GX with I fitted the engine to replace the angry one & its done nearly 40K since replacing them without fault.

Only over the last few weeks has it had some overrun smoke, buts thats also from fitting the turbo as well & mostly when backing off from full high rpm/high speed power runs.

So it should last a while!

[roccodingo]

You need to make sure the spring seat ( metal ring) is still on the head before fitting the seals also, they usually DONT fit over the installed stem seal.

great write up Pete.