Tech Gurus - Valve Adjustment Nut falling off into engine?

[ZCAT3]

I posted this in my DE story earlier, but thought I would ask this question as its own topic. I had one of the valve adjustment nuts back itself off of the rocker while on the track causing terible valve slapping noises. Lucky for me the nut made it into the oil pan without causing damage. How common is this type of problem? It sure seems like a pretty poor design.

Bill

[Rick Lee]

Never heard of this happening. If the nut was loose, I'm surprised the valve didn't get loose and make a lot of tapping noise before the nut came off. There should have been plenty of warning on this one. Sure you didn't hear anything?

[markwemple]

First I have heard of it. Usually it is a pain to lossen up those puppies! Someone must not have done much in the way of tightening.

[Dleong]

I had that happen when a valve hit the piston from overevving. People have told me you can duplicate the problem, by hitting a vibrating object with a hammer. At the time, I thought I was lucky nothing else happened,but a few events later, the engine blew. Never figured out if they were related incidents.

[ZCAT3]

Well I did the last valve adjustment myself almost 10,000 miles ago, so it seems I tightened them enough to last that long. There was no additional valve tap before the track day, but the over-rev suggestion does raise a possibility. The car has a Protomotive chip in it and the rev limit is set at 7000 or so. I have actually never hit it as I usually shift around 6,000 RPM, but I got very close to 7000 a few times on Monday and my wife said she hit the rev limiter. So maybe it is time to have a new chip put in there with say a 6600 limit.

I spoek to severla mechanics about this and they said that while this is a rare occurence it is not unheard of. I got luck in that the nut made it all the way through to the oil pan without getting marred at all.

[MOMO3.2]

I did my first valve adjust on my 87 Carrera 3.2. It seemed fine on the initial shakedown until I made some 6,000+ RPM runs. A loud ticking started and I immediately shut it down and coasted for home. I had the car flatbeded to a P-Car mechanic and he confirmed that an adjustment nut had come loose from a valve and was just about to get sucked into the motor.

This mishap was the result of my error. Honestly, for $250.00, I will be paying to have the valves adjusted from now on. That much money saved is not worth the headache.

Mike

[ZCAT3]

Mike - I hear you. But given that I went 10,000 miles and several track days I don't think I screwed up. One thing is for sure - I will definitely up the adjustment interval if I am tracking the car a lot.

[MOMO3.2]

I'm sorry ZCAT3. I did not mean to infer that you left the nut loose. Damn, the Internet can be tough to communicate on some times. I was just reflecting on that close call with the nut going into the engine thing. We both got kind of lucky.

Peace out!

Mike

[Grady Clay]

Bill,

You just have the Porsche gods favorably looking over you. The nut probably wasn’t as tight as it should be. The valve adjusting nuts will stay in place almost forever, even at 7000++ RPM.

Yes, if there is some trauma to the valve train (like piston-to-valve contact), all sorts of not good things can happen. Usually this only happens when you get in the wrong (lower) gear and the momentum of the car causes the engine serious over-rev.

Best,
Grady
gradyclay@hotmail.com

[126coupe]

I hate to admit this, but when I first started racing 5 years ago
I was just learning to work on 911 race engines. I thought
I double checked everything. I left one rocker arm bolt loose
it fell out, the rocker arm fell out(exaust side) and was blowing exaust
out the velosity stack. I found the rocker in the lower valve cover,
put it back together and ran all weekend!

I now triple check all fasteners on the race engines.
Doesnt take alot of extra time concidering its a
Hobby

[ZCAT3]

Mike - no offense taken. I have been beating myself up over this since Monday when I missed out on 2 track sessions during what was up until this incident a very good day. I probably did not crank #4 down as good as I should have and with the rev limiter (soon to be changed) at 7000 there is extra stress to deal with. I do feel lucky that I dodged a bullet (or a nut as the case may be).

Bill

[speeder]

A couple of observations, #1 would be that someone didn't tighten an adjustment nut properly, this "problem" is rare enough to be non-existent on pro-prepared 911 race cars that see much tougher duty than your street 911. Could I have done the same? Absolutely! But don't blame it on the car. They are tough stuff.

Secondly, when you say that you are amazed or lucky that the nut wound up in the sump undamaged, what else could have happened? I suppose that it could have just stayed in the cam tower, but it's not like it could have fit through an oil passage or the sump screen and wound up in a rod bearing. Have you taken a tour of any motor internals? Frankly, you could have driven the car for hours like this, you would have had a dead cylinder is all, (if it was an intake valve), maybe some backfiring. Good to keep up w/ these things, but you did not "dodge a major bullet" here.

[ZCAT3]

Denis - I have not, in fact, taken a tour of the motor's internals. A dead cylinder would be a pretty big problem in my mind (it was an intake valve).

[speeder]

It would only be dead until you put the nut back on and adjusted the valve. Then it would be alive again. Not a problem.

[ruf-porsche]

Originally posted by ZCAT3
I got very close to 7000 a few times on Monday and my wife said she hit the rev limiter. So maybe it is time to have a new chip put in there with say a 6600 limit.

I think that it would be cheaper to buy your wife another car to participate in DE, so if she over rev the engine and destroy the engine, it will be HER car that needs to be repaired.

[Wayne 962]

It's not too common - no need for people to become alarmed.

The nut could have become tangled in the cam and damaged it...

-Wayne

[speeder]

Hypothetically, I suppose that "anything is possible". But there are countless 911s running around w/ a piece of headstud+nut sitting in the cam tower, I've never heard even an apocryphal tale of one damaging an engine.

[ZCAT3]

ruf-porsche - My wife is actually a very good driver on the track - she is the one that pushed me into the DE scene. Just about every instructor who has been in the car with her has commented on how good a driver she is (you know it is really hard to phrase that in a way that minimizes the obvious comebacks . In fact, she is such a natural that she could probably drive competitively and be pretty successful (please do not tell her I said this).

As to what this could do to the engine, in my original DE post someone responded saying this happened to them and it created quite a mess - causing the entire bank of cylinders to seize when the nut got wedged in. In any case, I definitely am the nut that I should be more concerned with and I am glad to hear this is a very rare issue.

[zotman72]

Hey I was that someone, in my case it was at a DE, the nut was backing off and I was in line waiting for my run group to go out. I heard the ticking noise. I should have just parked the car but I did not want lose my paid-for time on the track.
Now I have been doing valves on my air cooled engines since the earlier seventies and I have to believe that I tightened the nut down. I attribute my incident to the loosing of the nut to either the high revving of my 2.4 S engine (~7.2K redline) or less appealing, my under-torque of the nut. That same engine is now sitting out in my garage with its covers off waiting for another check of the valves and the addition of new turbo style, exhaust covers. You bet those nuts will be tight when I finish.
HTH.
Check out this thread to see why it is important.
my 2.4S engine pain last summer

[speeder]

It probably bears mentioning that seriously over-tightening these nuts would be just as bad as leaving them loose; ie. they could snap at an inoportune time.

As a brilliant surgeon friend once told me, "The opposite of good isn't bad. The opposite of good is 'better'".

Translation: Tighten all fasteners to proper torque. Tighter than correct torque isn't "better".