At 03:09 PM 7/12/02 -0500, Patton Dickson wrote:
"There are instructions for using the Clikadjust at the MG Cars Enthusiasts' Club site. Follow this link:" http://www.mgcars.org.uk/electrical/Clikadjust_1.html "

Oh, how may we misinform thee? Let me count the ways. Man I hate it when the instructions that are intended to set you right are wrong. On the above mentioned web page the theory about how the ClikAdjust tool works is about right, but the explanation on how to use it has some fairly serious errors. The worst omission is that it doesn't mention the pitfalls or drawbacks of using this tool.

First it irks me just a little that the rocker arm is called a tappet, but other things being correct, I could overlook that, as there is a reference note reading "Rocker (or tappet)", and a picture to go with it. Chalk that up to a difference in dialect.

Next is a short dissertation on the problem with using a feeler gauge, this being a major selling point for the ClikAdjust tool. If the output end of the rocker arm is badly worn to the point of being seriously concave at the point of contact with the valve stem, it would indeed be hard to measure the gap correctly with a feeler gauge. My personal view on that point is that if the rocker arm is that badly worn it should be repaired or replaced, and it is not particularly difficult to dress the output surface of the rocker arm to clean it up. On a one-off basis it may even be cheaper to clean up the rocker arms than to buy the ClikAdjust tool (especially if you do it yourself and don't pay the labor charge). But for someone who makes a daily routine of adjusting valves on lots of old worn engines (and getting paid for it) it may well be cost prohibitive to repair all of the worn rocker arms that come through the shop, and this tool might then serve a very useful purpose. "Get this junker running and out of my shop, because the customer won't pay for a proper repair".

The first really glaring error in the example is the statement that the MGB valve ajuster screw uses a 5/16 UNC thread at 18 turns per inch, when in fact it is a 5/16" UNF thread with 24 turns per inch. When calculating the thread advance relative to the screw rotation this makes a BIG difference. You can recalculate the numbers accordingly and come up with .36 turn for .015" advance rather then the stated .27 turn. That in itself represents an error of .002" in the gap, and you would need 11 clicks rather then the stated 8 clicks (at 30 clicks per turn of the tool).

But even taking that into account the instruction is still incorrect, as it is ignoring the fact that the rocker arm is not a 1 to 1 lever. For the B-series engine used in the MGB (and MGA) the rocker arm lever ratio is 1.42 to 1 with the output end of the arm moving farther than the input end. This means that the intended .015" gap at the output end represents only .0106" motion at the input end where the adjuster screw is located. Recalculating accordingly, you will need 7.6 clicks (rather than 11) for the desired setting. Rounding that off to 8 clicks makes the final adjustment a whole lot closer to .016" rather than the intended .015". If you're really not that particular about this built in .001" round off error in the setting, maybe you should ask yourself why you need this tool in the first place.

Addendum September 6, 2004:
Apparently someone took my comments to heart. The above linked web page has been "corrected" by deleting references to screw pitch and rocker arm leverage ratio, and the method of calibrating the Clickadjust tool by calculation.

The next problem is that for someone who works on a number of different cars with various valve gear geometry you would have to keep a sizeable chart of the various number of clicks required for different engines. If you can't memorize the entire chart, or if you don't have it pinned on the wall nearby, or if you don't carry it when you're traveling, then you need to keep in mind the procedure for calibrating of the tool on the fly. You may need to recalibrate it every time you work on a different engine. In the case of your own car when you don't use the tool very often you might even forget the setting (OF syndrome) and have to recalibrate it every time you use it anyway.

To avoid having to note or measure thread pitch and rocker ratio and do a number of calculations each time, you can use the feeler gauge method to calibrate the tool. As noted on this web page, this method requires the use of two different thicknesses of feeler gauges. This is about equivelant to the process of adjusting two valves with a feeler gauge, and it is also subject to the same requirements of finesse of touch (a learned skill) and the resulting possibility of error from the two successive settings. But it is a universal procedure which does not require any calculations.

The next point that is not mentioned is that succcess in using the ClikAdjust tool depends on having a free running thread on the adjuster screw, and in the rocker arm, and in the jam nut. It is fairly common on these older engines for some DPM to have overtightened the jam nut resulting in a stretched thread which may bind considerably when you are trying to adjust it. So unless you are intimately familiar with each and every engine being worked on, and are certain that the adjuster screws do not bind, you would need to take the time to run each adjuster screw in and out a few turns to be sure they are not binding, and if any screw does bind in the thread it must be repaired before using the ClikAdjust, all of which increases the time required to do the valve adjustment.

So you may soon determine that this new tool may not be a time saver at all. In fact it may well take longer just to learn to use this tool than it does to adjust the valves in the traditional manner with a feeler gauge (and misinformation doesn't help). Also consider the fact that the ClikAdjust is a single purpose specialty tool, where the feeler gauge set is a more universal tool good for a lot of other uses. I tend to shy away from such specialty tools as they cost a lot of money and tend to fill up garage space as they accumulate. As this tool is somewhat larger than a feeler gauge (and also redundant), I would never carry it in my traveling tool kit. I do occasionally feel the need to do a valve adjustment on the road or at a friends house, and I also do an occasional road trip that is long enough to merrit a valve adjustment in the middle of the trip. So for perhaps as many as half of the valve adjustments that I do this tool would not be available even if I did own it.

Bottom line is, I can think of other things I'd rather do with the money, but if you insist on living with badly worn rocker arms, maybe you could use one of these things.

$.02,

Barney Gaylord
1958 MGA with an attitude