Valve Stem Seal Replacement

[pgackerman]

I'm preparing to replace the valve stem seals on my 1988 2.8L.  The Haynes Manual on page 77 Section 4, step 6 says to:
...bring the piston of the affected cylinder to just before TDC on the compression stroke.  Feed in a long piece of 1/4 inch cord through the spark plug hole until it fills the combustion chamber. <snip> Rotate the crankshaft with a wrench (clockwise) until a slight resistance is felt.

I have two questions:
1) How long is a long piece of 1/4 inch cord?  I managed to feed in 11' - Yes, 11 FEET.   That seems a bit much.  Are we talking 1', 2', 5'?

2) How do I know I'm at just before TDC on the compression stroke and how much more should I turn the engine after feeding in the cord?

Guess that was three questions.

[Raydar]

Go ahead and remove the valve covers and all the spark plugs. You're going to have to do that, anyway.
The cylinder will be on the compression stroke when both valves are closed. Stick a (preferably) wooden dowel into the cylinder, and let it rest on top of the piston. Carefully turn the crank pulley. You will be able to feel when the piston is at (or approaching) the top of its travel, by feeling what the dowel is doing. Be careful not to let the dowel get bound up, and break off. The cord that you're feeding into the cylinder is to stop the valves from dropping down onto the piston, or into the cylinder. (If you fed in 11', the piston is still way down in the cylinder.)
An alternative is available if you have an air compressor and a sparkplug adapter. (If you have a compression gauge, the "screw-in" adapter should work fine.)
It doesn't really matter where the piston is on its stroke.
Remove all of the rockers. Mark where they came from. They need to go back in the same place.
Connect the compressor to the cylinder, and pressurize it. Full pressure is fine. You generate much more than that, every time the spark plug fires.
Once the cylinder is pressurized, you can do all the work you need to do to replace the seals. The air pressure will hold the valves closed.
It really would be a good idea to have the piston at the top of its travel, in the cylinder that you're working on. If the pressure drops, for whatever reason, the valve still shouldn't drop into the engine.

If anyone sees any flaws with this method, please comment. It's what I was planning to do when I replace my valve springs.
 
 

[pgackerman]

Guess I should have mentioned my 1.5 rockers will be replaced with 1.6 rockers.
Does that change anything?

BTW, I don't have an air compressor stronger than a bike pump, nor do I have the sparkplug adapter.

[Fierofool]

So that you don't have to go through the valve readjustment process, get yourself the Lisle Pushrod Removal Tool number 48500.  NAPA carries Lisle and I think Pep Boys and O'Rielly does, too.  You can swing the rockers out of the way and do the work.  If you want to remove the pushrods, get a 2 x 4 and drill 6, 1/4 inch holes in it in pairs of 2 and place the pushrods in them, in order.  Mark one end of the board Front, for the waterpump end of the engine so you know how everything goes back. 

I have a loaner if you have time for me to mail it to you.  But, if you're doing the 1:6 rockers, you won't need it.  Got to go through the process anyway.  http://www.gafiero.org/bbs/index.php?topic=2049.0

[Raydar]

Guess I should have mentioned my 1.5 rockers will be replaced with 1.6 rockers.
Does that change anything?
...

It's all essentially the same. Still have to remove and replace the rockers.

[pgackerman]

Managed to crush a dowel today.  Didn't snap off.  Told myself I was lucky and called it a day.

Try again tomorrow.

[Fierofool]

Something that works extremely well as a wooden dowel is the bamboo skewers for shiskabob.  They will splinter but usually don't break apart.  They're about a foot long so they give you plenty to work with.  If you follow the cylinder sequence in my link, you can know which to go to next to insert your rope without having to rotate the engine exessively. 

Be sure to use plenty of shop towels to cover the oil return and pushrod galleys so you don't loose a valve keeper into the engine. 

[f85gtron]

Use a magnet to catch the keepers