Valve adjust question - no rocker movement

[ant7]

I think we are all intrigued to find out what the heck is happening here now!
I realy hope you get to the bottom of this, and i [like everyone else here] will be keeping an eye on this one for updates.
Anthony.

[gordner]

Have no insight to add to this discussion, however to the fellow who posted about the dowel, I am an aircraft maintenance engineer and it is a standard practice to probe the piston with a long phillips screw driver to verify tdc on piston aircraft engines. They tend to shy away from risky practices maintaining aircraft, so for this to remain a standard practice in aviation is basically a statement that no one has ever done significant damage doing so. I do the same on my vehicles as a double check and have borescoped those same cylinders and have never seen any damage from this practice. The only thing to watch out for is dont get the dowel in the plug whole when the piston is too far down as it can cant over on the way up and jam.

[McLovin]

Originally Posted by jlynch1960

Finally, just went to a spot in the cam rotation where I was certain the rocker was not on the lobe and did the adjustment there.

I read through the thread quickly, and saw a lot of discussion about making sure you are at TDC, dowl in sparkplug hole, seeing where distributor rotor is pointed, etc.

I may be missing something, but that all seems irrelevant.

As you posted in your original post (quoted above), you can see when the cam lobe is pointed away from the rocker. For a valve adjust, that's all that matters.

If you visually confirm that the cam lobe is pointing away from the rocker on your problem valve, your problem isn't TDC, etc. All that can be eliminated.

[CCM911]

Thank you so much. I was really getting annoyed at the messages that all but called me crazy. I have been playing with cars and motorcycles for over thirty years now, so I kinda know what works and what doesn't.

Originally Posted by gordner

I am an aircraft maintenance engineer and it is a standard practice to probe the piston with a long phillips screw driver to verify tdc on piston aircraft engines. They tend to shy away from risky practices maintaining aircraft, so for this to remain a standard practice in aviation is basically a statement that no one has ever done significant damage doing so. I do the same on my vehicles as a double check and have borescoped those same cylinders and have never seen any damage from this practice.

[911pcars]

[QUOTEOriginally Posted by ivangene]
+1 for NOT sticking wood into your spark plug holes [/QUOTE]

Originally Posted by CCM911

Hey, I was being kind. I usually use a phillips screwdriver. Other than using a dial guage, how is he to know that the cylinder in question is at TDC? When the piston is at the end of its travel and the distributor rotor points to that cylinder, you are in the firing position. At that point, both valves will be in the closed position, allowing OP to get his feeler guage in place.

It helped me. Obviously you guys have other methods.

Not sure about the aircraft combustion chamber layout and valve type you refer to, but in a 911, the poppet valves angle toward each other and become perilously close during the overlap period. Introducing another object in this region through the spark plug opening (especially a rigid steel object) while rotating the crank can create all kinds of interesting scenarios. YMMV.

This would be the safest engine format for inserting a probe:
Redirect Notice

And as described, removing one or more spark plugs to confirm piston/valve position is superfluous labor when there are simpler and less time consuming methods to do this. Again, YMMV. Several ways to skin the cat.

Sherwood

[CCM911]

Regardless of technique, I really want to know what is going on here. Why would a valve not want to adjust?

[911pcars]

Originally Posted by CCM911

Regardless of technique, I really want to know what is going on here. Why would a valve not want to adjust?

Could be several things. Are you the orig. owner? If not, there were many chances by POs to change things up.

Post a pic of the offending valve. Maybe the audience here can observe some visual tell-tale signs. It couldn't be that you're trying to adjust when the valve is open, could it? Just checking.

Sherwood

[jlynch1960]

Mystery solved - I'm a #%^&* moron!

Tried this again Sunday afternoon. Worked fine.

After wasting all this bandwidth, I think the difference came from having dabbed some paint on the pulley hash marks to take pics for this thread. Rotating the crank took some effort since the plugs were in (I had to pinch the belt hard to get it though a couple of spots) and looking at the pulley, it has some scaled/chipped paint that I can see now I could easily have mistaken for one of the marks. I'm glad the paint's there and hope it stays there for the next 15k miles.

Wow, do I feel like an idiot.

Thanks for the help and insight people offered and sorry taking up a lot of people's time on such a rookie error. My bad, as they say.

Jim

[safe]

Don't worry, I'm pretty sure everyone here have done stupid misstakes at least once...

But in the future don't focus so much on the pully marks, they are quite irrelevant when doing a valve adjustment....

[ivangene]

I for one feel great you solved it!!

like they say, you dont know what you dont know...now you know!

[Driver_X]

+1 for Perserverence!

[hcoles]

another example of "it is usually something simple"

when I adjust valves I always look in with a flashlight to see that the rocker pad is on the low part of the cam lobe (high part pointing 180 degrees away from the pad).
Sort of a belt and suspenders approach, which I tend toward.

[Jesse16]

One item I found happening with my valves that I didn't see mentioned in this thread as follows. During the top end part of my rebuild, I found that 3 of the 12 adjuster screws had threads that were damaged or stretched such that they would only turn a short bit before jaming in the female thread of the rocker. Made them "feel" tight to varying degrees when trying to turn with a screw driver. Because all was apart, I used a dremel and cut them off and installed new screws which moved smoothly. I could not see the issue just looking at the screw threads but they were definately bad. Maybe something happened one time in the past with the previous owner, maybe overtightened, maybe they don't last forever, who knows. The valve adjust I did just prior to the rebuild was my first and was fairly interesting as I remember, trying to get the screws to move and adjust smoothly.

[lindy 911]

An expert is someone who has made all the mistakes possible in a narrow field. You are now on your way.

[dhagood]

Originally Posted by jlynch1960

Mystery solved - I'm a #%^&* moron!

congrats on solving your problem. and if i had a dollar for every time i've mumbled that exact phrase under my breath i'd be able to get my 3.2L engine professionally rebuilt with money left over

[dfink]

Yes just glad to hear you got it and nothing horrible happened in the process.

[CCM911]

I hate so say I told you so......

But I KNEW that your piston was not at TDC.

Glad to see you are now OK.