1963 MK2 3.4 Automatic with a 1967 S Type 3.4 engine. When I'm cruising down the motorway and I lift my foot off the "GO FAST" pedal and then press down on it again, I can see a puff of blue smoke in my rear view mirror.

Two knowledgeable friends have told me the valve stem seals need replacing. How big a job is this?



Stu

 

Hi Stu, there are 2 ways to change the valve seals, head off and usual procedure for taking valves out etc.

The second option requires applying compressed air into the spark plug hole, you need to take the exhaust cam out, then apply air to a cylinder to keep the valve shut, and remove the valve springs, change the seal and put the springs back on, repeat for all 6 cylinders, cam back in and off you go.

You need the adapter to apply the compressed air, and the correct spring compressor to do the job this way, it's a lever type rather than a clamp type, but it saves a whole bunch of work removing the head.

 

This can be done as TJon instructs, but I've found (with any engine), that if the seals are shot and there is enough play in the guides to let oil by to the point where it's noticed in the exhaust, that it's time for a head rebuild.
Depending on how bad the guides and stems are worn, the new seals will wear out more quick due to the play in that area.

 

Jeff is correct, it will depend on the mileage, if the guides are worn, you may as well do the head as Jeff has said, you can see if the valve seals are perished due to age by taking off the cam cover and checking with a small screwdriver to see if they are brittle. Sometimes they can even fall apart, you will soon spot that.

This like a lot of jobs is a weigh up on how far you go. If you are doing this yourself and have the kit, you can do as I have said, but get the piston in question at TDC then after the springs are off, release the air pressure and wriggle the valve about, they usually go oval and you can feel the wear fairly easily. You need the piston at TDC so the valve wont drop into the cylinder, you need to lift the valve by hand and reapply the air to proceed any further.

 

Generally smoke when you lift your foot off the gas is worn valve guides, smoke when you push the accelerator is bad rings. My experience is with Jeff- seals are generally less of an issue that the guides.