911 Valve Lash Adjustment Tool

[dkirk]

As a 911 owner now for the past 5 years, I must say that I enjoy working on this air-cooled masterpiece almost as much as driving it. However I quickly learned there were a few jobs that just aren’t fun; one of these being valve lash adjustments with the engine installed in the car. The combination of tight access to the valve/rocker arm area, the use of thin “tin foil” feeler gauges that are easily destroyed, and generally cramped quarters in the engine bay, lead to a frustrating and time-consuming experience. After my second lash clearance adjustment, I knew there must be a better way of doing this job.

After some thought, I arrived at what seemed to be a logical alternative. Knowing the rocker arm lash adjuster screw pitch (1.0 mm/rev) and the desired clearance (.1 mm), it’s straightforward to calculate the amount of turn required to attain the .1 mm clearance from a zero lash baseline. This is the principle upon which this valve lash adjuster tool works, i.e., just like a micrometer. With adjuster screw lock nut loosened, the tool is placed on the rocker arm with driver bit engaging the lash adjuster screw. The knob is rotated clockwise to get a metal-to-metal, zero clearance baseline. At this point, the moveable pointer is then rotated to align with the baseline mark reference. The knob is then rotated counterclockwise to the .1 mm reference line and proper clearance is established. Tighten the lock nut, and clearance is dead-on the money. And should tightening the lock nut cause the adjuster to rotate (as it sometimes does), it is easily seen on the adjuster knob and can be compensated for.

After constructing a prototype, I first tried it on my own ’88 911, then on two other friends 911’s with excellent results. It really cuts down on the time (and more so the frustration) in doing a lash adjustment. I can’t claim that the job has now become “fun”, but it certainly less of a pain when compared to the classical method. A few 911 owners have seen this tool and have encouraged me to go into production with it, and that’s what I’m planning to do. I’m proud to say that this tool is being offered exclusively on our host’s website and here is the link:

Porsche 911 & Carrera Cam Towers & Timing Chains - Page 3

A few pictures of the tool follow:





I’ve strived to make this a functional, quality tool for a good value and something that would be complimentary to the mechanical beauty of the Porsche 911 engine.

[Lapkritis]

Nice work Dave - this will be on my list for spring time. Time to retire the ribbon of shame that I had been using as a feeler.

[cgarr]

Nice, Years ago when I suggested using the 1mm pitch screw as a mic to set lash was not received well, pretty damn accurate plus it takes up any wear in the feet and valves stems that a feeler gauge will not. Nice Job!

[Flat6pac]

To get the best results you need to go out past the .1mm and close to the .1mm taking the thread play into account. My check is with the dial guage and fixture to the near stud to the rocker.

[RedCoupe]

Looks like a quality tool. My toolbox needs one of these! This method of setting valve lash is tried and true - I once bought a tool using this principle at a garage sale and used it to adjust the valves on a old Chevy six. My old tool wasn't this nicely made, however. I think it was from "Western Auto"!!!

[snbush67]

Looks great, one word of caution; do not tighten the tool once the elephant foot contacts the valve, to avoid compressing the valve spring.

[gsjohnson]

Very impressive. I gotta have one.

[nickyclyde]

Ordered one!

[dmark9]

Nice looking tool. Look forward to trying it.

www.pfixit.com

[fasterlaster]

This is fantastic. It's on my project list for the next Pelican order.

[frannyB]

Hi Dave,

That looks really sweet! I've been using the "back-side" method and I really like the go/no-go aspect, but even after going through three or four complete cycles, I think I still have a loose one that is making a fuss.

I have a question: How do you compensate for the slight change when tightening the set nut? Seems like when I do it I have it just so and as I tighten the nut, it goes loose a tad. I then have to guess a little as to how much affect the nut will have and back it up a little and thus starts the back and forth... And with the back-side, you measure from the top and adjust from the bottom and vise versa. Up and down...

Another quick question, the screwdriver slot on the top of the adjuster is huge compared to every screwdriver I have. Does your drive foot compensate for that? Is it a nice snug fit?

This looks awesome! Thanks so much for taking the time to work it all out!

Oh, do you think this will work on a 356? The adjustment isn't so bad, but it would be nice if it worked on both cars...

Franny

[toddu]

I don't think you use a screw driver to adjust, you turn the big red knob.

Todd

[Jdub]

I think Franny has anticipated the natural slop of screwdriver end to screw (the slot is oversize and not a solid fit to the tool end) and is asking about that latitude in adjustment - is it compensated for?

[toddu]

Ah, misread it as "on top if the adjuster" of the tool. Got it now (need more coffee).

Todd

[KTL]

Originally Posted by cgarr

Nice, Years ago when I suggested using the 1mm pitch screw as a mic to set lash was not received well, pretty damn accurate plus it takes up any wear in the feet and valves stems that a feeler gauge will not. Nice Job!

Maybe a lot of people don't realize that a micrometer's precision is based on threads, just like the threads in the rocker adjuster screw?

The feeler gauge method would be fine if the foot wasn't in such a bad position to bend the feeler gauge. Backside method is close enough for me.

But a real nicely executed tool nonetheless. Nice job Kirk.

[304065]

I just bought one.

One of my new years resolutions is to do more frequent valve adjustments. I use the z-block and a clock usually, but that is a lot of setup. And the feeler gauge method requires gaging "feel" like a micrometer-- I've checked my feeler gauge job with the z-block/clock method and it's not perfectly repeatable for me.

I look forward to trying this out and checking the repeatability.

Craig, maybe you are finally getting some respect around here

[Lapkritis]

Would like to see a video of this in use. Somebody must want to be instructional video/demonstration famous.

[SoCalSK8r]

This tool looks awesome and well designed, I'm definitely buying one!

[dkirk]

Gentlemen,

Thanks to all for the compliments and suggestions – greatly appreciated. Will try to address some of the questions and concerns that have been brought up:

1. Valve spring tension in the 911 engine is high enough that it cannot be overridden by tightening the tool knob with one’s fingers – impossible.

2. Thread slop compensation is accounted for as the jam nut loads the threads in the same direction as when the zero-lash load is applied to the threads. Hence, when the adjuster is backed off the proper number of degrees from zero clearance and the jam nut is tightened, you are assured of exactly .1mm distance between the elephant foot and the valve stem. You may have to think about this a bit and draw a sketch or two, but it’s a fact.

3. The driver bit (screwdriver) on this tool is held to a tight width tolerance. The slot in the adjuster screw has a slight taper, and the bit is designed to engage this taper about .75 % of depth, thus there is no angular slop in the fit that could possibly contribute to error.

4. The suggestion of a video is a great idea. I’ll do this after the weather warms a bit. Have a friend that needs an adjustment and will use his car as the specimen. I do include a 4-page instruction sheet with every tool which explains proper use in detail, but an instructional video is always the best. I don’t necessarily seek YouTube stardom, and fearing that my ugly face may frighten some, I’ll try and find a pretty 20 year-old female that can demonstrate the ease by which this tool operates.

Thanks again guys.

[Caledonian]

I think your tool is great for a home mech like me and I would like to buy one, do you a have a distributer in Australia?