Valve adjustment gone bad

[Aurel]

I went to bed at 3:20 am last night, after starting my valve adjustment at 9:30 pm. There was something wrong, I noticed when I was adjusting one rocker, another one was totally loose. I double checked everything, the clearances were always OK for the piston at TDC, but another rocker always remained totally loose. Again, I redid it over and over, and this wasn`t my first valve adjustment. I had removed the spark plugs, maybe not a good idea.

This morning I put in the oil and it started right away, but with an awful clicking valvetrain noise, so I shut it off and I am confirmed I have to redo it again .

Questions:

1. What could have caused this?
2. Did my short start test cause any damage?

Thanks,

[Gunter]

Elephant foot kaput?
Rocker shaft moved?
Broken spring?

"the clearances were always OK for the piston at TDC, but another rocker always remained totally loose"

Which piston?
Which other rocker?

[Aurel]

Well I did it all over again, and same problem: Say I was adjusting valves on cyl#3, so it has the correct gap, but then cyl#1 and #2 I did before will have loose rockers. It is a general problem that occurs on all the cylinders. If I recall correctly, the piston at TDC should have rockers free to move from the value of the gap, but all other rockers should be tight, correct? I also noticed that in order to adjust the gap, I had to unscrew the adjustment screws on all of them. This is driving me nuts.

[tabasco]

If the problem occurs on all the cylinders, I would think something's wrong in your procedure.

You mention doing it in the order 1-2-3.
That's not the TDC order when you rotate 120 degrees (1-6-2-4-3-5), so you must be rotating more than 120 degrees, right ?
Or you don't time at TDC, which is OK as long as you're not on cam.

Which method and which tool do you use ?
Can you describe what you're doing ?

Regards,

-Guillaume

[Aurel]

I did it in the correct order (1-6-2-4-3-5), I was just saying that when I finished #3, #2 and #1 were loose. I use the 0.04" tool sold here, and the standard method (not backward). I did it before, never had this issue. I am fearing broken valve spring, but could it affect the entire procedure?

[Brando]

Sure you weren't 120º off? I've done it before! Caught it before I turned the engine over, though

[Aurel]

I`d rather have done something wrong than having a deeper mechanical issue, but I can`t see what I could have done wrong: I started adjusting cycl#1, with Z1 lined to the centerline, and the distributor facing the notch. Then went on from there by 120deg increments to cyls#6-2-4-3-5.

[Oh Haha]

Interesting.

Did you have the noise before you did the valve adjust?

If not, it must be the way you are doing it. If so, then you may have a problem.

Do you leave the feeler in place when you tighten the lock nut?

[Brando]

I noticed in your sig it says you have DC15 cams... Does that mean it has irregular cam timing? Should you be adjusting a few degrees before or after TDC?

[Aurel]

Originally Posted by Oh Haha

Interesting.

Did you have the noise before you did the valve adjust?

If not, it must be the way you are doing it. If so, then you may have a problem.

Do you leave the feeler in place when you tighten the lock nut?

I had a little bit of exhaust pop-pop before I did it, and yes I leave the feeler in place when I tighten the locknut.

Brando, DC15 cams use the same valve lash as SC cams. And I did it before with those cams and the car was running great.

[Gogar]

What if you adjust each valve, and then turn 720 and check? Does it stay?

I don't know if it would make a difference, but perhaps you could do one side at a time, turning 240 degrees and do 1,2,3.

[Grady Clay]

I agree, this is most likely a procedure issue. Even if not, lets carefully examine the exact procedure. Only then can we examine other possibilities.


Once you have access, oil drained, valve covers off, etc.; you need to rotate the engine (CW at crankshaft pulley) to TDC compression for #1 cylinder. There are two TDC choices: compression and overlap with the “Z1” mark aligned with the mark on the fan housing. The easiest method is to note if the rotor is pointing to #1 terminal and not #4 on the distributor cap.

If the rotor is pointing to #1, the next check is to confirm that both the intake and exhaust rockers on #1 have ‘click’ clearance.

Going to the next cylinder in the 1-6-2-4-3-5 sequence involves rotating the engine by hand with a wrench on the crankshaft – 1/3 rotation, 120°

It might be worthwhile to go through the complete 720° (two complete rotations) of the crankshaft checking each pair of rockers for ‘click’ clearance. It is useful to confirm that the rotor is pointing to the terminal of the cylinder you think.

Next is probably the measuring and adjusting technique. The cam housing design does not make this easy but we have been doing this successfully for 43+ years. Make sure you have your technique correct and your tool is correct – some have an improper angel. Each valve has a slightly different position and technique with the tool.

Setting the correct adjustment is a “feel” issue and that makes it very personal for something that is very mechanical. Become mechanical.

The type and amount of lubricant has an effect on the measurement technique. Cold, sticky lubricants will skew the settings – usually to the loose. At room temperatures, WD-40 works well. Just be sure you re-lubricate with proper oil before moving the engine to the next cylinder. The lubrication cam lobe-to-rocker arm is critical. Other, not so much.

Tightening the lock nut is the critical operation. It changes the setting. You must hold the (screwdriver) adjustment while tightening the locknut, anticipating the movement in adjustment (usually to loose depending on technique). This is the “art” of valve adjustment. It is useful to devise your own tools specific for this operation.

The “feel” of the movement of the tool with a tight, correct and loose valve is very small and subtle. If you have the opportunity to practice on a fresh engine on a stand, do so! If not, repeat your process many time to develop the feel.

Carefully inspect each feeler gauge stock for your tool. Edge burrs can fool your use of the tool. They can be removed with some 800-grit paper. Never use a wrinkled gauge. It is useful to have several tools (bent differently) to check your work.

Valves set too loose just make noise and don’t do any damage. It is possible to set a valve tight with no running clearance and still get the tool out from between the valve and elephant’s foot. Always reinstall the tool for ‘feel’ and check for ‘click clearance’ after you think you are finished.

Never be afraid of going through several 720° rotations checking your work. Good ‘professionals’ do that every time.

Moving the rocker axially on the rocker arm shaft is an additional ‘click’ check for clearance. It is useful to check for proper shaft position and fastener tightness.



Critical for a good, long lasting valve adjustment is driving situation. An engine with combustion debris (‘carbon’) on the valves and seats can be adjusted to spec. When the carbon burns off (like on the highway or an event), the clearance closes up – perhaps dangerously. A proper valve adjustment can only be preformed with the valve properly sitting on its seat, not interfered with carbon debris. ‘Carboned up’ valves are best left alone – so long as there is some clearance..



Our nice old 911s are relatively high maintenance engines. They also like (and were designed) to be run hard. They run best being run close to the ‘limit’ and done so regularly. “Resting quietly” was not a 911 design criteria.

When these cars were new, I would not have hesitated to buy a new one and drive to Daytona , run the 24-hour and drive home. My ‘street’ 2.8 engine sorta did this - finishing.


Best,
Grady

[psalt]

I also noticed that in order to adjust the gap, I had to unscrew the adjustment screws on all of them. This is driving me nuts.


This is not unusual and it is not unusual for the valves to make noise after an adjustment. Valve clearances get smaller as the valve seat and face wears, and the purpose of the valve adjustment is to make sure you have enough clearance to get rid of heat and not burn a valve. It is a misnomer that "noisy valves just need adjustment", most of the time it is wear in the guides, stems and rockers that is responsible for the wear. If you adjusted the valves to the correct clearance, do not try to chase noise by tightening them. Only rockers under lift should be tight, if the valve is open and you can feel play, it is in the rockers.

Paul

[Aurel]

Maybe a clue here: I looked at my distributor, and when it is pointing towards the notch, it fires cyl#4. Cyl#1 gets fired when the distributor contact is opposite to the notch. Is this normal? Also,
someone please confirm that all rockers should have no play except the ones for cyl@TDC.

I am going to redo it considering I was starting wit cycl#4 instead of 1. Hope that was the problem.

[psalt]

The notch in the distributor is for #1. The distributor can be installed incorrectly and the plug wires rearranged to compensate. It is irrevelent to a valve adjustment.

My advice is to forget about trying to follow that procedure, which is designed to save you time that has already been lost.... Observe the valve and rotate the crank until the valve is closed and the rocker is on the heel of the cam. Then measure the clearance. Check the rockers for lateral play in the bushing.

[Grady Clay]

Simple. Forget ‘notches’ and such.

Simply look at which spark plug wire the rotor points to. Unless the engine wasn’t running prior, this is the cylinder to adjust. Physically follow the wire.

The finesse is only having the mark on the pulley align with the mark on the fan housing.


Over the years is it possible for engine ignition wiring, caps, rotors and distributors to be changed. Sometime for the ill. That is an issue for another thread. All you need to know is what cylinder is at TDC compression and finesse it with the pulley mark.


When you have the distributor off the engine, there are a complete other set of instructions. I don’t think that is the case here.

If every pair of rockers required great adjustment, I suspect there is confusion between TDC #1 compression and TDC #4 compression cylinders.

Even with outrageous wide clearances, you can tell where the engine is at, re TDC. Get to where you are at TDC and you have clearance on both #1 valves. Check that #4 has no clearance. Even with wide adjustment, #4 should have both valves open.

Another check is to look at the adjustment screw threads. The number of exposed threads above the lock nut should be consistent and appropriately about three threads.


If you removed the distributor at the same time as this valve adjust procedure, we have another set of issues. All recoverable.

Best,
Grady

[Rob B]

Did you state that you were using a .040 feeler gage? I'm sure it was mm but the " after .04 signifies inches, but I could be wrong. Rob

[mpetry]

and maybe getting at what Aurel's reporting.

Get to where you are at TDC and you have clearance on both #1 valves. Check that #4 has no clearance. Even with wide adjustment, #4 should have both valves open.

So when any valve is at TDC with both rocker arms on the base circle (ready for adjustment) there are at least some other valves that could be adjusted. I'm just thinking of a sequence (possibly more confusing?) that one could adjust all the valves in the engine in a smaller # of turns.

I use the backside method which is FANTASTIC, and I do 1 side of the engine at a time, so turn the crank 240 degrees per increment. I think I will look around with a flashlight - next time I'm in there - and see if there is an even more streamlined approach. I know in the 356 world you could do #1 and #4 on the same crank rotation, and then 2 and 3. I'm thinking this might work, however the trade off would be going across both sides of the engine. Easy to get mixed up.

Feeling for that little "wiggle" that indicates the rocker arms is on the base circle is the key. Even when #1 is on TDC, there are other valves that will have that same play - say intake for #3 and exhaust for #5. This is perfectly normal, nothing to worry about.

Mark Petry
Bainbridge Island, WA
81 SC

Seen in a bike shop:
Our Labor Rate: $50/hour
If you watch: $75/hour
If you help: $100/hour
If you worked on it first, screwed it up, and then want us to fix it: $200/hour

[Aurel]

Grady was right: I was starting at TDC#4 instead of TDC#1 because the distributor was installed that way (which I should have known since I am the dumbass who rebuilt the engine). Now all is good, I just wasted a large portion of the week-end at it, my wife is mad at me, and I didn`t get to go fishing...but I have a hopefully happy 911 (didn`t even have time for a test drive).
Thanks all for your help.

[Oh Haha]

Sweet.

Next time, start a little earlier in the day.