Despite appearances, I am making some progress toward remedying the
"weird noise" in the VW engine in N891JF. I'm still not exactly sure
whether it was excess play in the cam's thrust bearing, or it was
excessive gear lash between crank gear and cam gear....because it had
BOTH, and they both sounded very similar. Replacing the cam bearings
with a new double thrust cam bearing (the old one was double thrust
also) reduced the end play to about .002", which is a big improvement.
Next was gear lash, and the cure for that is to replace the cam gear.
Sounds easy enough since the engine is completely torn down anyway, but
replacing the gear turned problematic.
The gear was fastened to the camshaft with three Allen button head
bolts . I hate Allen headed bolts, especially in a high torque
application, because you're starting out with a practically rounded
hole, and the Allen wrench is IFFY at best. I clamped the cam gear in a
vise (with "soft jaws") and the first bolt I tried to loosen refused to
budge and stripped right out. For the next two, I heated them up with a
torch to soften potential Loctite, and hit them with a half inch air
powered impact wrench. They reluctantly came out. I then WELDED the
impact wrench into the stripped bolt's hole, and while it was still warm
enough to loosen the Loctite, I hit it with the impact wrench.....and it
immediately broke the Allen wrench! Now what? I can't drill the bolt
out, because it's so close to a cam lobe that I can't get the drill in
there to access it anyway. Then I looked up the strength of those
particular bolts, and they are M12.9! I could waste more time breaking
drill bits and getting frustrated, or I could just order another
camshaft with a new gear and be done with it. That sounds easy, but
apparently low end "stump pulling" VW Type 1 camshafts are apparently a
thing of the past.
I spent a couple of hours trying to find a cam like what I had and
found nothing. Years ago, I spent a lot of time researching cams in
aircraft applications, and determined the Eagle 2280 to be the best
option. I found it in a few places...."OUT OF STOCK" with no expected
IN STOCK date. I looked at other options, and finally found an Engle
W100, which is similar in profile, with only "ONE REMAINING" and
pounced on it. It should be here in a few days.
A good machinist could probably get that broken bolt out somehow, but
they're so busy in this town they don't even answer the phone, and the
wait time is equally ridiculous. It never hurts to put a new cam and
lifters in it anyway. I'll get it back together eventually. Meanwhile,
back to the hangar to finish building a work bench addition.....using
TORX head screws!
--
Mark Langford
m...@n56ml.com
http://www.n56ml.com
Huntsville, AL
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