911 adjusters versus stock, valve adjusters Options

[r_towle]

While I have read alot about the 911 adjuster and I have everything I need to use them. I have a simple question.

why use them?

It seems to me that if I am using all stock parts, stock cam, pushrods etc...am I gaining anything from using the 911 swivel foot adjusters?

A big gain for me would be to increase the frequency between adjustments...that alone may make it worth it.

IC one potential issue. The original adjusters are designed to twist the valve with each impact...that keeps the valve moving BY DESIGN.

The 911 adjusters, with the swivel head, would be less likely to twist the valve as much...once friction comes into play at the swivel head, it will twist the valve some...but not as much as the solid adjuster.

The arguement that it works on a 911 is not valid...this is not a 911 motor and all the metals are not the same...


So, what are the positive reasons for using these adjusters?
What is the risk of not using the solid adjusters? (the valve turning risk)

Rich

[aircooledtechguy]

You get a more accurate valve adjustment with the 911 adjusters. Consider the surface contact on the tip of a stock adjuster; it's rounded or in the case of most adjusters in use has many flats/points on it. The 911 adjuster gets a way more accurate adjustment with a feeler gauge and then is a lot nicer to the tip of the valve stem over the life of the motor. Stock adjusters will often times wear a slight bowl in the tip of the stem, 911 adjusters will not giving you less frequency of adjustment due to wear.

I personally have never built a performance motor without them and would not consider doing so. My .02 FWIW. . .

[ChrisFoley]

Rich,
You will get more valve lift with the stock adjusters, so you shouldn't use the swivel foot ones if you're looking for cheap ways to make more power.

[SLITS]

Hah ... I'm gonna chime in ... The only reason I can see to use them is to lessen the side loading of the valve. The stock rocker slides across the tip of the valve which is why the stock rocker tip is arced. This pushes the valve stem against the sidewall of the guide ... side loading .. and supposedly promotes wear of the guide. They seem to last 100K+.

The elephant feet should lessen the tendency to side load the valve due to it's design.

A roller rocker is much more effective at reduction of valve side loading.

[r_towle]

Rich,
You will get more valve lift with the stock adjusters, so you shouldn't use the swivel foot ones if you're looking for cheap ways to make more power.

I am not looking for more lift, but I certainly dont want LESS....

A point in the CON column.

Rich

[McMark]

(IMG:style_emoticons/default/confused24.gif) If the rocker ratio remains the same, what does the adjuster have to do with valve lift. (IMG:style_emoticons/default/dry.gif)

The only benefit that I can see is decreased wear between the adjuster and the valve tip. The swivel foot becomes a bearing, of sorts. I can't see the swivel foot reducing side loading. All other things being equal, the amount of friction causing side load will not decrease with a swivel foot. It will actually increase because of the larger contact patch. Try stopping your car with brake pads the size of a pencil eraser. Smaller contact = smaller friction.

Edit: See below where I retract this position.

[SirAndy]

Try stopping your car with brake pads the size of a pencil eraser

I sure hope you have good liability insurance! (IMG:style_emoticons/default/biggrin.gif)

[Katmanken]

Ummmmm...

McMark, friction is not dependent on surface area.....

At least that's what they taught me in engineering school.....

Larger pads do lower the force on the rotor, provide larger heat transfer areas, and increase the force required at the pedal for the same braking.....

Pencil erasor sized brakes would exhibit low pedal force, really high heat, and REALLY high wear.....

Per the 911 adjustors, they may work better with large lift cams

[r_towle]

Jake has a motor in his 912 I think that uses the swivel foot adjusters and the steel pushrods that he has never, or almost never adjusted the valves...

If that is the result...I am in.

Aside from that point, I do not see a huge value in these adjusters, except maybe when you are trying to get the feeler gauge in there...it would be alot more consistant I suppose.


I still have no opinion, and I have yet to hear lots of definitive opinions one way or another.

Rich

[McMark]

McMark, friction is not dependent on surface area.....

In this example (valve to rocker contact) the force involved will remain constant. So my brakes example was misleading. Forget that example.

Force from the valve spring will remain constant, lift speed will remain constant, intertia will remain constant. In that scenario where only the size of the contact patch increases, the friction increases.

But admittedly this scenario is much more complicated, the more I think about it. Because you want a certain amount of friction to rotate the valve. So perhaps the increased friction is a benefit because the valve spins more.

I rescind my previous comment upon further thought.

[Bartlett 914]

Jake has a motor in his 912 I think that uses the swivel foot adjusters and the steel pushrods that he has never, or almost never adjusted the valves...

If that is the result...I am in.

Aside from that point, I do not see a huge value in these adjusters, except maybe when you are trying to get the feeler gauge in there...it would be alot more consistant I suppose.


I still have no opinion, and I have yet to hear lots of definitive opinions one way or another.

Rich

Isn't the reason we need to adjust the valve clearance is due to the valve and valve seat wear? If this is the reason, then the adjuster should have little effect unless the adjuster and the valve tip are being worn by the solid adjuster.

[r_towle]

McMark, friction is not dependent on surface area.....

In this example (valve to rocker contact) the force involved will remain constant. So my brakes example was misleading. Forget that example.

Force from the valve spring will remain constant, lift speed will remain constant, intertia will remain constant. In that scenario where only the size of the contact patch increases, the friction increases.

But admittedly this scenario is much more complicated, the more I think about it. Because you want a certain amount of friction to rotate the valve. So perhaps the increased friction is a benefit because the valve spins more.

I rescind my previous comment upon further thought.

There is the rub for me.
Does it really rotate the valve more with the swivel foot/rotating head of the 911 adjuster?

Rich

[ChrisFoley]

(IMG:style_emoticons/default/confused24.gif) If the rocker ratio remains the same, what does the adjuster have to do with valve lift. (IMG:style_emoticons/default/dry.gif)

The arc on the adjuster isn't concentric with the axis of rotation. So as the valve moves down, the point of contact moves outward on the adjuster, thereby increasing the rocker ratio at the point of maximum lift. QED.

[McMark]

Sure, but by that logic we would be running out adjusters out as far as possible and running shorter pushrods to maximize valve lift.

[ChrisFoley]

I didn't say that it made good sense, just that it lifts the valves further than swivel feet. (IMG:style_emoticons/default/wink.gif)

[orange914]

i've noticed a BIG reduction in the "old thrasher/lawn mower" sound of the engine

Try stopping your car with brake pads the size of a pencil eraser

I sure hope you have good liability insurance! (IMG:style_emoticons/default/biggrin.gif)

we live in ca... do we NEED insurance??? (IMG:style_emoticons/default/icon8.gif)

[Jake Raby]

Jake has a motor in his 912 I think that uses the swivel foot adjusters and the steel pushrods that he has never, or almost never adjusted the valves...

If that is the result...I am in.

The engine in my 912E saw it's last valve that needed to be adjusted on February 3rd, 2002.. That was over 130,000 miles ago. Today the engine has 152K recorded and none of the valve train components have been swapped. I have checked the valves fairly often, but none have needed any adjustment, so I have let them go just to see what happens.

The last time I checked the oil was 6 months ago, the last time it was changed was in July of 2007.. It just keeps going and going, but is VERY tired! It has lost about 30 HP over the years, but still makes more power at the rear wheels than it's flywheel HP rating when new.

The swivel feet adjusters are part of the reason I can do this, but the main reason is the other valve train parts I am using as well as all the valve train being cryogenically enhanced along with the rest of the engine components.

EVERY engine we build gets 911 adjusters, I like the hydrostatic dampening of the swivel foot and the wear reduction that the stem of the valve sees..

With all stock components in the valve train there isn't really much to gain, honestly..

I have never noted any losses or gains with stock or swivel foot adjusters.

This post has been edited by Jake Raby: Jun 21 2009, 09:21 PM