Is there a "while you're in there" for an oil change? (Valve adjust? Gasket?)

[yelcab1]

Originally Posted by Bob Kontak

Well stated.

skillset = general curiosity, patience, diligence and that healthy smidgen of fear. Fear helps with the second two.

Well, except for ...

Changing out torsion bars,
Changing out rear wheel bearings,
Changing out rusted exhaust studs,
Fix the rear main seal leaks, or the bearing number 8 oil leak.
Fix the "can't get into first gear" thing
let's not forget the "head studs broken right at the base" issue.

Those require special tools, machine shops, or big balls of steel, in addition to your 13mm wrench.

[MattTHEpainter]

If anyone wants to borrow my Kirk valve lash tool just drop me a PM. I won't be needing it for awhile.

[BE911SC]

Originally Posted by yelcab1

Sometimes an oil change is just an oil change.

And in the air-cooled 911 world it only snowballs from there!

[Bob Kontak]

Originally Posted by yelcab1

Well, except for .....................

Those require special tools, machine shops, or big balls of steel, in addition to your 13mm wrench.

It requires diligence.

I don't have a mill to line bore cases.

Study will lead me to a rational decision to farm that one out.

[Bob Kontak]

Where's sugarwood?

I am going to ride your ass like a Christmas pony until you finally lift a wrench in anger against that car.

Pieholio dubs thee: THE MIGHTY LEGHORN

[sugarwood]

Matt is sending me his Kirk tool, and I will have a go with it.

In the meantime, I need to order valve cover gaskets.
My lower valve covers are the Turbo type.
The $32 set has green/silicone lower gaskets.
The $22 set has all 4 grey lower gaskets, which is the one I ordered

[sugarwood]

Ok, I now understand how the Kirk tool works. Feeling more confident as I wait for my gaskets to arrive. I might replace my spark plugs while the upper valve covers are off.

I have 2 stupid questions:

1) If a valve is already correctly adjusted, you should only be able to screw it down an additional 36 degrees, before hitting the stop, right?
How exactly do valves get out of adjustment in the first place? I'm assuming the lock/jam nut doesn't get loose so what is making the valve move in the first place? Cam lobe wear?

2) Why is there a gap in the first place? Why not just have the rocker arm connected directly to the valve stem? What does the gap accomplish?

[A horse with no name]

It's relatively quite simple...Heat expansion. Try to look at it in that there is a little "tug-of-war" going on... actually a 'push-of-war.' To allow for the satisfactory operation of either a cold or warm engine (expansion of linkage parts and valve stem lengths change the lash a little), and to allow room for gradual wear between adjustments. The trick to valve adjustment is to strike an appropriate balance between opening the valve as far as possible and making sure it closes securely. There's a 'lot of heat' being generated, and a valve that is set to tight will ' burn' the valve, and if they are too loose they don't close properly. Intake air -> exhaust out.

The 911's, as you know, have Overhead Cams, hence no rods to 'push' up and down.

By placing the camshaft directly (nearly) on top of the valve stem, you eliminate the inherent inertia of pushrods, and the engine can rev to higher RPMs with greater ease. There's still a little bit of linkage, and it still uses something similar to lifters, but since now they're being pushed down instead of up, they're called cam followers. Overhead cam engines require a much longer chain. The maintenance of the chain in Carrera's is really a non issue anymore with the introduction of hydraulic tensioners in the 3.2 Carrera's

Now, on a non overhead cam engine, the valve spring is trying to keep the valve closed, and the cam lobe is trying to push it open, through the linkage of the pushrod and rocker arm. If any of those many linkage parts start wearing, the dimensions change, and if the valve surfaces hammer themselves into the seat, the dimensions change in the other direction.

I hope that this helps you understand 'why'

[sugarwood]

Thanks, that was a nice explanation.

Ok, so the gap is to allow for 2 different sizes the valve can take, due to thermal expansion. If it was a fixed linkage, the valve would not fully close when hot, since the valve stem would be longer.

But, exactly which part starts to wear down, requiring an adjustment? Does the end of the valve stem get dented in after being pressed so much. Does the base of the valve get worn down from hitting the seat so much? Wouldn't the spring that pulls it closed just handle that automatically?

[darrin]

Sugarwood -- this seems to answer your question -- Why do the valves need to be adjusted? - Ninja250Wiki

Valve heads and seats wear faster than the cams/etc. While the springs would keep pulling the valves shut, the wear on the combustion chamber side will outpace the wear on the camshaft side, resulting in the camshafts preventing the valves/springs from allowing the valves to completely shut. So, valve adjustment is primarily focused on maintaining the gap necessary for the valve springs to enable the valves to completely shut and account for the differential in wear between the combustion chamber side of the valve and the camshaft side of the valve

Make sense?

[sugarwood]

Ok, so the valve seat gets worn down. This makes the valve sit "deeper", if you will, in the seat.
This makes the stem protrude higher, reducing the gap. This would change the timing of when the valve is pushed open (sooner).

It just seems weird that the valve seat can get worn down, yet still work effectively. I'd think it wouldn't seat properly anymore.

[75 911s]

FWIW I'm doing a valve adjustment now. I know you have the tool but if you decide to try a feeler gauge this might help you locate the gap.

I marked my feeler gauge for depth with a line. It makes it a lot easier to find the gap. It's home made with some tape at the end for grip.

[darrin]

Originally Posted by sugarwood

Ok, so the valve seat gets worn down. This makes the valve sit "deeper", if you will, in the seat.
This makes the stem protrude higher, reducing the gap. This would change the timing of when the valve is pushed open (sooner).

It just seems weird that the valve seat can get worn down, yet still work effectively. I'd think it wouldn't seat properly anymore.

Sugarwood -- Beleve that's exactly the point -- if you don't adjust the valves, they'll end up staying partially open and causing catastrophic damage

[sugarwood]

Ok, I now have all the stuff, and I will attempt this before Sunday.
Oil and filter. Valve cover gasket kit. Kirk tool.

I have a few outstanding questions in the meantime...

For the valve adjust, I pretty much loosen the lock nut, turn the knob/screw clockwise until it hits, and then back it off CCW the marked amount.
Then tighten the lock nut. And I do each intake/exhaust (top and bottom) at the same time, right?

If the valve is already perfectly adjusted, I will only be able to turn the screw the exact same 36 degree angle I am supposed to back it off once it hits, right?
I will end up back at the exact same marking on the Kirk tool?

How exact does the TDC mark have to be on the crank?
If the valve stays closed for an entire cycle, doesn't that give a lot of leeway since the valve will be fully seated for a period of time as the crank wheel spins.
In other words, I don't have to nail TDC exactly, since it's not closed for just a split second. Is that sort of correct?

On a 1986, will there be stuff in the way?
Will I have to remove anything like the A/C?

Is it helpful to have a 2nd person to provide a 3rd hand for any task?
Like to tighten the lock nut while I hold the Kirk tool steady?

[dan88911]

Have you read these: ajusting valves

Valve Adjustment - First Timer

[dan88911]

There is more

911 Valve Lash Adjustment Tool

Porsche 911 Kirk Engines Valve Adjustment Procedure | 911 (1965-89) - 930 Turbo (1975-89) | Pelican Parts DIY Maintenance Article

[dan88911]

And
Porsche 911 Valve Adjustment - The Backside Method | 911 (1965-89) - 930 Turbo (1975-89) | Pelican Parts DIY Maintenance Article

[sugarwood]

I need to remind myself that non-Synth (VR-1) oil change interval is only 3k-5k.
I've gotten used to going 5-7k with my DD with Synth.
And, I'd rather err on the side of caution with an older for, for some reason.

Only been 5 months, but I think I am going to change it again this week.
Kendall seems cheap at $46 for 12 quarts.