I bought a set of the German 911-style valve adjusters and solid spacer kit from bugguy1967 on the Samba who also machined my rockers and blocks. He mentioned that the adjusters should be set up with about a 1mm offset from the valve center line. I thought the offset was only needed for the stock adjuster to induce valve rotation but didn't apply to the 911-style adjusters. I have mine set up dead center on the valve stems. Do I need to move some shims to add some offset?

I have two votes for setting up the valves with offset in my build thread (3 votes if you count the machinist). There is conflicting information on other forums with some saying that spring winding as it loads and unloads contributes more to valve rotation than the adjusters. Others sticking with the "offset is good" approach.

I made a diagram to show why this isn't making sense to me for swivel foot adjusters. The diagram on the left shows a stock adjuster with small contact area. It is easy to see how moving the contact area slight off center of the valve stem causes the adjuster contact area to swipe across the stem face to induce rotational movement. But if you look at the wider contact patch of a swivel foot adjuster, you see there is almost as much contact area left of the valve stem center as on the right. Assuming the force of the swivel foot is distributed evenly across its face, this means there is almost as much force swiping in opposition of rotational movement as in the supposed direction of rotation. I question whether offsetting swivel foot adjusters really benefit from better valve rotation. At the same time, I question whether moving them to center on the valve stem has any benefit other than satisfy my OCD tendency toward symmetry and alignment.

Click to view attachment

I have a set headed my way from Bugguy1967 also so I'm watching this thread.
I'm starting to get my parts together for a 2056 build in the near future.

"My OCD" could be a problem

Oh, it most definitely is That, and as a scientist, I'm a trained skeptic so have this crazy demand for evidence.

I can understand the thought process. When I set mine up it just so happened the solid adjusters were a few thousandths off center. The swivel foot still covered the entire valve stem. I only knew I was off center when checking with the original adjuster I could see the swipe through the sharpie mark. While I'd like to think that the minor offset would turn the valve with every hit I was ok with letting it go and to no longer stress about the minor details of making the engine last to the millionth mile and just get it built to last 100k which it probably would never get to in my lifetime

Curious...did you go with the adjusters that buggyguy sells? Or the official Porsche ones?

I went with the Thorsten Pieper adjusters the bugguy sells. I've seen nothing but good reviews on them so hoping to continue that trend. A couple nice features for them are that they are available in 8 and 10mm size so you don't have to source 1.7 liter rockers to put them in a 2 liter. Also, they are very close to the same overall length as stock adjusters so should be no issues with them hitting the valve covers.

I sent my Rockers and blocks to him to do the machine work. They came from a 1.7 and have the 10MM adjusters.

I bought the adjusters, collars and shims from him.

Almost is not the same as equal. The valve will rotate less but it will still rotate unless the forces about the valve stem centerline are equal.

Personally, I'd rather have more valve rotation than less. No rotation will be problematic for wear and thermal effects.

Agreed. Valve rotation isn't just important for the foot/stem tip interface. That swivel is needed for both maintaining thermal equilibrium across the valve face and cleaning carbon off the seats.

Now if 1 mm is the correct number, that's a good question. Too far and you'll side load the valve resulting in faster valve stem and guide wear.

Thanks everyone for indulging me with these crazy questions. Looks like it is unanimous that even the swivel feet should be set up with a little offset, so I will fall in line although I remain skeptical. I'm not questioning whether valve rotation is necessary and good. That seems beyond debate, but I'd love to see some data showing that offsetting swivel foot adjusters has any real positive impact on rotation. I might just have to try a little experiment

Do you guys really think the adjuster spins the valve?
It's the wrapping and unwrapping of the the valve spring that spins the valve.

The adjuster should sit a little offset, so the foot spins and wears evenly. The offset is okay as long as the adjuster's center is still over the stem.
Yes... you're over thinking things.

That was a given from the very start. That's kind of my thing. But you've given me a good reason to believe that offsetting the adjuster has a real benefit. Now I think I'll be able to sleep tonight.

Sheesh . . . a doubting Thomas.

Not sure what experimentation you have in mind, but, know that measuring at quasi-static conditions will have no representation on valve rotation. You would be failing to capture the high acceleration loads imposed upon the valve train when operating at speed.

Unless you have a test rig that has Laser Doppler Vibrometry I'll wish you even more luck in observing and/or measuring the valve rotation.

I'm looking at a graph in a SAE paper 2012-01-0159 written by some gents from a company called Porsche and the rotational speed of the tested exhaust valve is nearly static until cam speed reaches 2000 rev/min. At a cam speed of 4000 rpm the valve rotation peaks at about 4 degrees per camshaft rotation.

Unfortunately I'm not finding the paper that outlines the effect of 911 elephant foot valve adjusters upon valve rotation as modified for application on a VW Type 4 engine.

If you're seriously interested in the paper text me.

Not to be a complete dink . . . and I'm not saying you are wrong and/or the spring doesn't contribute. The spring surely does contribute, but . . . what about a Desmo valvetrain?

There are plenty of valve mechanisms out there that are designed to induce valve rotation either with or without a spring. Not a great paper but gives some examples of other rotation mechanisms.

"In case of the valve trains with rocker arm, the valve rotation it is generated by the offset position of the rocker in relation with the valve axis (Figure 10)"

https://bmwmotorcycletech.info/valve-rotation.pdf

If the valves are rotated by the coiling and uncoiling of the springs won't they come back to the same places on the valve seats? I am far from an engine builder, but I was under the assumption the off center action caused the valve to slightly rotate.

I once worked for a chap who told me "you are not getting paid to think"

Doesn't the swivel foot adjuster rotate as well? I have seen a grown man turn an unloaded one with his pinky...

Not just a doubting Thomas, but a professional doubting Thomas . You confirmed my suspicion. The experiment I was thinking was just to set up a pair of valves dead center and another pair offset. Mark the valve stems and spin the engine by hand a bunch of cycles and see if there is a difference in rotation. I already suspected engine speed to be a factor so expected it to fail but hey, it's about the journey.

I am interested in that paper and will text. I'd also settle for a paper on the effect of 911 elephant foot adjusters on valve rotation on a 911 engine.

They'll still end up in a different spot every time and that's enough. Valve keepers (stock) don't clamp onto the valve stem groves, the valve will spin on the groves.
For high performance I grind the keepers so they do clamp on the keeper groves and you'd think they would no longer spin, but they still spin... it's a pretty violent action.

It's like clocking the ring gaps, really you only have to get every 2nd one 180* from the first, once you start the engine they'll all start to spin (unless they're pinned).
In many cases you want things to spin, it evens out the wear.

I always find amusement in the religion around ring gapping. Quite a few papers written around the topic there too. Mythology of engines lives on.

You are absolutely correct that it's not so much how the rotation occurs but that it must occur to some degree to keep the wear relatively uniform.

From my armchair, I agree. I would surmise a few degrees would be enough, just to keep things from "taking a set"