911 Valve Adjusters for my Type-4 2.0L?, Good Idea or Bad Idea? Options

[ericread]

Somewhere earlier I saw a comment that Jake had recommended using 911 Valve Adjusters in the Type-4 engine... Or maybe he had recommended against it. I can't remember.

Anybody out there have experience in this? My adjusters and adjuster nuts were pretty gnarled when I got my car a few years ago. Now with bi-monthly adjustments, I'm looking to replace them.

Will the 911 adjusters fit the existing rocker arms? Do I need the same nuts? If I go ahead with this, should my properly adjusted valves run quieter? And is there any advantage to replacing the springs?

As a result of some moderate leaky valve guides, my plans are to have the heads re-built this winter. Should I wait until the heads are rebuilt, or is there any reason I shouldn't go ahead with the adjusters, nuts and springs right now?

Any thoughts?

My thanks.

Eric Read

[type11969]

Okay, if you won't draw it out . . .

Crude drawing of the valve train, approximates what the t4 has close enough to prove a point.

Stock adjuster set with appropriate geometry (adjuster inline with the valve stem) at half lift:

(IMG:http://i19.photobucket.com/albums/b188/type11969/stockadj.png)

Now, pretend for a minute that the valve spring will just stay compressed so that when you pull the stock adjuster, nothing moves. Geometry is still the same. Cam is still rotated to half lift for that rocker, lifter is the same length, pushrod is the same length, rocker is rotated about the shaft (which hasn't moved) by the same amount:

(IMG:http://i19.photobucket.com/albums/b188/type11969/noadj.png)

Now, put the porsche adjuster in. You can see that by simply swapping what the adjuster looks like does nothing to change the geometry:

(IMG:http://i19.photobucket.com/albums/b188/type11969/porscheadj.png)

Now the problem is, as you can see in the above picture, that the porsche adjuster foot will interfere with the stock rocker, which is why it needs to be clearanced (blue box below):

(IMG:http://i19.photobucket.com/albums/b188/type11969/porschadjclear.png)

Final product:

(IMG:http://i19.photobucket.com/albums/b188/type11969/porscheadjfinal.png)

The only thing that changed in any of these pictures was what the adjuster looked like, and clearancing some of the rocker to allow for proper adjuster function. Everything else is fixed, as it is in your engine, because simply changing what the adjuster looks like does not affect the length of the pushrod, position of the rocker shaft, etc. Set the lash the same between the stock adj and the porsche adj to get the contact face in the same plane relative to the valve stem and everything else will fall in to place.

Now if you have to shim to get enough clearance for the adjuster to work properly then you are moving the location of the rocker shaft relative to the valve stem and cam so you will definitely need to change your geometry.