Broken Rocker Adjustment Screw

[splischke]

I had something unusual (for me) happen today when performing a routine valve adjustment. The adjustment screw on the #3 intake rocker arm broke in 3 pieces when I loosened the jam nut. See the attached picture. My first thought when I turned the wrench was "boy this jam nut is loose" but then I realized the adjuster was actually broken and just hanging on by habit or something. I know some people are saying that I must have over-tightened the jam nut in previous valve adjustments but I know I didn't. This adjuster is only 75 hours old and was purchased from Great Plains.

-Scott

 

[n3480h1]

Wow, that's a little scarey. I don't think you overtightened it, because the rocker and nut threads are a lot more malleable and they would give first. Glad it stayed together long enough for you to find it. I hate to think what might have happened if those chunks had migrated over the departure end of the runway. I've never heard of a valve adjuster screw coming apart . . . ever. I'm sure Steve will do everything he can to prevent this from ever happening again.

Maybe you should go buy a lottery ticket, Scott: This could have turned out much worse.

Tom

 

[Gaston]

Glad for you it ended this way...


Strangely, I find the color of the steel much darker than what I usually see...

Gaston

 

[Schmleff]

Could it have come loose first and then the hammering action broke it?

 

[splischke]

Could it have come loose first and then the hammering action broke it?

Don't know. I do know it wasn't loose when I finished my last valve adjustment 25 hours ago and I never-ever had an adjuster nut loosen by itself.

 

[n3480h1]

Gaston makes a good point. From what I can see at screen resolution, the metal appears very dark and grainy, a texture similar to cast iron. I don't have a clue about the metallurgical specifications for these parts, but if they are cast, then I'll have mine scanned for voids and inclusions. If they are not cast, then perhaps metal fatigue crystalization, or simply the wrong heat treatment, neither of which should ever happen - but they do.

I hope we can learn the cause because there are an awful lot of VW valve adjusters out there. I'm not a big fan of "engine out" conditions.

Tom

 

[splischke]

I wonder where my adjusters were manufactured? Are they VW NOS or imports? I hope Harbor Freight isn't involved All I know at this point is that they came from GPASC and were brand spanking new.

I have 7 more adjusters on the engine and perhaps all are from the same manufacturers lot. I think I'll replace them with my old adjusters.

-Scott

 

[JuergenA]

Hi Scott,
I take this one:
http://www.csp-shop.de/cgi-bin/cshop2/front/shop_main.cgi?func=det&wkid=954478371466&rub1=Engine&rub2=Valve%20Train%20%2F%20Cylinder%20Heads%2CRocker%20Arms&artnr=10884a&pn=0&sort=&all=
I don't know the original manufacture, but I think, it willl be Scat:
http://www.scatvw.com/RockerArms.htm

with best regards
Juergen

 

[Gaston]

Scott...
is there a reason why you don't use big foot with swivel ??

Gaston

 

[splischke]

Scott...
is there a reason why you don't use big foot with swivel ??

Gaston

No particular reason other than I started with stock adjusters and they have worked just fine for the past 325 hours. I continue to think they are okay to use. Statistically getting a bad stock-type adjuster that would break at the relatively low RPM we run our engines must be extremely low or we would hear about more failures. Statistically speaking, swivel feet adjusters can break too.

-Scott

 

[Gaston]

I didn't mean swivel were statistically any better than stock adjusters...
I was just curious...
I would be curious to compare this particular broken adjuster with some others fore hardness...
maybe a destructive test on the grinding wheel would say something interesting...

Gaston

 

[mike1]

The way it fractured appears to be a too hard issue. As in brittle. it would be interesting to know their method of manufacture.

 

[Des]

Hi all,
I heard that use of the "elephant feet" is disadvised, because it may prevent the rotation of the valve during operation.
Normally, it is required to observe a small dull circular pattern on top of the valve stem, this to indicate the "off center" position of the thumbler striker hits the valve stem at the right location, and the valve is indeed rotating during operation..
When this pattern is not present, but indications of more or less a stripe is present, it may indicate "something is wrong", and should be investigated...
Am I correct here, or was I told nonsens?
Best regards,
Frans.

 

[JuergenA]

Hi Frans,
the "elephant feet" sit not in the center of the valve top, it sit some 1/10mm out of centre and so, this give the valve a little push to rotate.
with best regards
Juergen