Cold Butter and Valve Adjustment

[lothian]

I’m preparing to do a valve adjustment procedure on ’00 V6 VTEC.

Valve lash is adjusted (as documented in both the ‘Honda Service Manual’ and ‘ALLDATA’, and demonstrated in many online videos) by feeling for “drag” with an appropriate feeler gauge. My question: given the tolerances involved, how is it that this procedure does not require the precision of a strain gauge?

Here’s an example typical of the language one may expect to read/hear detailing the most critical part of this job:
“Snug down the rocker “just” until you begin to feel resistance. You should be sliding the feeler gauge back and forth or side-to-side gently. The valve lash setting should not be tight… the feeling should be about the same as putting a table knife through a stick of cold butter. Not too hard, not too soft.”

Seriously..?

A bazillion years of valve adjusting by eleventy-bazillion greasy digits and the procedure has never evolved beyond this sort of casual approximation..? I’m incredulous. Precision is implied; dire consequences warned. So why the conspicuous lack of any semblance of exactitude or required use of a seemingly purpose-built tool (e.g., strain gauge) for this job? I use a torque wrench to tighten the lug nuts on my Accord to 90lbs. I could simply tighten each nut by “feel” with a four-way to, say, three grunts of snugly goodness. But I risk a warped rotor. How then did “a stick of cold butter” become an accepted method to gauge tolerances of a thousandth of an inch within an interference engine?

In my purple-sky world, here’s how I imagine the valve lash procedure reads:
“Attach the strain gauge to appropriate feeler gauge as spec’d by Honda valve lash setting. Slide the feeler gauge between the top of the valve stem and the rocker arm tip. Zero the strain gauge. Loosen the jam nut. Slowly tighten the adjustment screw while drawing the strain gauge back. Tighten the jam nut when the strain gauge reads [whatever Honda specs as the appropriate value a strain gauge tool should read when used in this application]. Move to next valve and repeat.”

Bleh…

Topic

[Mike]

Because being a technician requires the right “feel”.

If you don’t have it, all the tools in the world won’t help you.

[Ingvar]

Buddy of mine, 18 yrs engine mechanic, does not even use gauge. He does exactly that – feels the gap between two fingers. Does it perfect every time.
Otherwise, you’ll need to come up with a dynamometer attached to the feeler gauge to match drag to a spec.

[Andrew Phillips]

[quote=”lothian” post=139241]Here’s a example typical of the language one may expect to read/hear detailing the most critical part of this job:
“Snug down the rocker “just” until you begin to feel resistance. You should be sliding the feeler gauge back and forth or side-to-side gently. The valve lash setting should not be tight… the feeling should be about the same as putting a table knife through a stick of cold butter. Not too hard, not too soft.” [/quote]
I’ve never read a description like that in a factory service manual. I would expect to see something like that in a Haynes, because those manuals are targeted for DIY consumers, not auto technicians. Technicians (aka mechanics before the term technician was used) are trained in the use of tools and how to ‘feel’ measurements (hence the name ‘feeler gauge’) for adjusting valves, measuring other clearances, and setting gaps on spark plugs (and the now-archaic ignition points). You just have to acquire the muscle memory and feel recognition to do the job; which only occurs through repetition and practice. It’s a different world today with so many high-tech digital tools, purpose-built ‘special’ tools, and software-operated components and computerized diagnostics. But with that said, a lot of repair procedures still to this day require hand-eye coordination, visual attention to detail, discriminating touch and feel, recognition of odors and sounds, and many other acquired skills that go beyond the relatively simple acts of turning a wrench or squeezing a plier.

[Mike]

I learned valve adjusting with feeler gauges. It’s a clearance range that covers a few feelers at least. I always chose to tighten it up so only the thinnest feeler specified would fit in the gap. Who cares about drag? If it fits without the feeler blade distorting because it has to be jammed in, then it is that clearance. On Honda-style, it’s especially easy to just grab the rocker arm and wiggle it by hand to feel the clearance. I would describe the feel as being ‘only enough that you can feel the play’.

Strain gauges are an engineering tools as opposed to a field service tool. That’s the kinds of things they use to determine the clearance spec that they give us to work with.

[Author]

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