There's a couple ways you can do it.  Most are going to say use air pressure to hold the valves closed, but I read an article years ago that was pretty intriguing where they talked about a method that used a greased rope.  Any way you do it you'll need a spring compressor.  Just like adjusting the valves you'll want the cam on the base circle before removing the rocker for the valve you're working on.  Broad strokes I know.  I'll see if I can run down that article...

MS once explained about stuffing the cylinder(s) with rope and bringing piston to TDC.
Gotta do it 8 separate times but...at least you won't need a new gasket and all the other associated thangs.
Run thicker oil for a while. See if that helps?!
6s6

Is there a problem with the detritus left in the cylinder by the rope material getting scraped off and deposited down in the cylinder?

MS wrote:

Rope trick is simplest way I know of. Just put piston at 180degrees before top dead center, remove spark plug, insert about 18” of 3/8” braided rope, then, by hand, rotate the engine towards TDC until it won’t turn any more.

Then remove the rocker arm and bolt a lever type spring compressor to the rocker stud. Remove the keeper and retainer. Replace the seal. Put retainer and keeper back in place With rocker.
Back off the engine rotation and pull out the rope. You DID remember to tie a knot in the end of that rope, didn’t you?

This is by far the easiest way to do this with out any dropped valves. Please do not axe me how I know this. 
 

Last edited by RV6 (6/22/2020 6:15 PM)

I've used the air in the cylinders with valve compression tool many times and it works fine. never any problems.  The air tool screws in the spark plug hole and holds the valves up tight.  When you first put the air to it, it will push the piston to BDC.  Make sure the air does push the piston to BDC.  Then remove the rocker arms and use the spring compression tool.

retired65 wrote:

I've used the air in the cylinders with valve compression tool many times and it works fine. never any problems.  The air tool screws in the spark plug hole and holds the valves up tight.  When you first put the air to it, it will push the piston to BDC.  Make sure the air does push the piston to BDC.  Then remove the rocker arms and use the spring compression tool.

 
I would think having the piston at the bottom is a recipe for possible disaster. If, for whatever reason, the valve was moved and compression is lost, the valve will drop into the cylinder and require head removal to fix it.  If I were using compressed air, I would lock the crank position so the piston was at the top so the valve could not come out.  You will be messing with the valve keepers and retainers, and they sometimes require a little effort to get them to come loose.  In a perfect world, the valve would NOT come loose and break the seal, but we don’t live in a perfect world.  I prefer a fail safe method!

Nos681 wrote:

I used nylon rope trick when I did it.
I like the idea the valve cannot fall out.

FYI, not all spring compressor tools are of same quality.

That is a neat tool in the video.
Never knew it existed.

 
A hundred bucks a pop for the Lisle tool versus 50 cents for a piece of rope.
Talk yer pick!
Now if you used one every day, that’s  another story.
If anyone has one I can look at, I’ll spin one up in the shop.

Last edited by Rudi (6/23/2020 12:09 PM)

I did mine a few years ago and used air.  I used the hose from my compression tester and an adapter fitting to my air compressor.  Just screwed the compression tester hose into the plug hole, turned on the air and left the air on until I was done with that cylinder.  Didn't pay any attention to the piston position but did listen for air flowing around the valve before I compressed the valve spring.

I borrowed the spring compressor tool from O'Reilly's.  

I left all the spark plugs in except for the one in the cylinder I was working on and didn't have any issues with anything moving inside the engine.