Valve clearances won't stay the same....also turning the engine CCW...truth or myth?
 

Well still trying to get the SC running after installing 964 cams...

hard to get a full day of free time to work on it...

so I started with the simple stuff...the spark and fuel seem OK

so I decided to check my valve adj before ripping into my motor to start from square one and re time the cams

well I can't seem to get the clearance to stay the same.

I'll get it right...do some other valves...and just to check my work as I go, I check earlier valves and they are tight again...I can't even get the blade in...

what gives??

This happened one my first time around...so I ended up essentially doing about 5 adjustments till I was able to get 2 consecutive measurements on all the valves...and I thought that was good enough

I read through the archives and I noticed some of you have to rock the rocker all the way on it's heel to get the blade back in...so I am gonna try that after this post...but I don't think that is it cuz I usually rock ther rocker back and forth just to make sure there is some sort of gap...

I am thinking it could be caused by the cam nut being loose the sproket has some play around the pin, but I double-checked all my fasteners...

well let me know...or else I am just gonna tear down to the cams and start with a clean slate

ALSO

while reading the archives I noticed ominous warnings about turning the engine CCW...well I'll admit I did this on occasion when I missed a crankmark...or when I missed TDC #1 and did't want to spin the motor 720 degrees to get back TDC...

is it really that bad for the tensioners/engine??

I have noticed the same. The valve clearance is so small, even an oil layer can cause the false adjustment. When I do my valve adjustments, I don't adjust the valves by marks, i just check when the rocker arm comes to top position -> Valve closed. Then I adjust that valve.


Rotating the engine CCW is bad thing (in my opinion) if the chains and the other stuff is so worn inside that the chain can jump...Otherwise, why would it hurt anything?

well I found that being a perfectionist I tightened the valves too tight and ended up being too tight...thus even though I could get it in and out the 1st time around...after a couple turns I couldn't get it in...

redid them, kept them slightly looser...the result?...see this thread...

http://forums.pelicanparts.com/porsche-911-technical-forum/104469-itzalive-its-alive-its-aliiiiivvee.html

The reason you don't want to turn the crank CCW is that it can effect the crank to cam relationship. If you miss the mark a little and turn the crank back (CCW), the cam might not even move because of the slack in the chain. If you miss the mark, turn the motor CCW for half a rotation and then turn it CW to get to the mark. The idea is to get take up all the slack in the "system". This is a lot more important when timing the cams.

When you installed the cams did you coat them with assembly lube? I've had too much lube interfere with cam timing - the valve clearances got larger as the lube spread out and got thinner.

-Chris

Just did mine on Sat. Number five exhaust kept changing just a little bit. I was thinking a carbon deposit between the valve seating surfaces? Is this a possability?

...or you may have a valve ready to break off on the stem. This happened on my VW after I ran into the same problem when I couldn't get a consistant adjustment on one cylinder. Motor eventually spit the valve head or piston material out thru the case. Talk about ruining the day.