Dial Guage for Valve Adjustment

rotorhead · 03-27-2005, 10:36 PM

I am adjusting my valves with the engine out, I put a dial guage using the Z block on the tip of the rocker adusting screw after making the adjustment using the special feeler guage. The Dial guage showed that there was nearly double the specified clearance (0.18 instead of 0.10mm) on all the valves I had adjusted.

Is the dial guage measurement the prefered method or is there extra clearance built in with the assumption a feeler guage will be used?

Steve

Oh before you say "you didn't use the feeler guage properly" I was careful that it gave a "magnetic" type of drag

hcoles · 03-28-2005, 05:15 AM

The mechanics I talk to tell me to adjust the screw so that it is fairly hard to wiggle and pull the feeler out. I like the idea of the dial gauge for valve adjustment. I made some fixtures using blocks of delrin but then found out that things didn't fit when doing some of the valves. If you do this you probably need to be careful how you push the "slop" when taking the measurements. Probably the ultimate way is to get the valves to open X amount at a certain crank degree this way the valves should all have the same effective duration. Of course you still want to maintain the 0.1mm lash.

That's my 2 cents.

-Henry

Rob 930 · 03-28-2005, 11:38 AM

I've always been a fan of using a dial indicator for valve adjustment, but it sometimes seems like I'm the only one who feels that way. I just don't think it's possible to get good "feel" when you're operating a feeler blade on a long fixture as is necessary for a 911.

I use an aluminum fixture to hold the indicator that was sold by Performance Products many years ago. (I haven't tried, but a Z block may work just as well.) The only trick to it, I think, is to be sure that the side play in the rocker arm doesn't "contaminate" the measurement. I place the dial indicator plunger on top of the valve adjusting screw, then with both hands I hold the rocker to one side of the cam box or the other, and I rock the arm back and forth, while observing the swing in the needle. Sometimes surface tension from oil in between the adjusting foot and the end of the valve causes it to "stick," so a little force is needed to be sure you overcome it. There's no need to "zero" the dial, just rock the arm several times and look for .004 in (.1 mm) swing on the dial face. To adjust the valves is a by-guess-and-by-golly proposition. If the clearance is too loose, I loosen the locking nut, tighten the adjusting screw and retighten the locknut (fully) and remeasure. If I'm off, I try again. It doesn't take long to do. And when I'm done -- I'm sure my clearances are at 0.004 in. with very little error.

As a test, I once had a very experienced engine builder adjust several valves on my engine using his preferred method and tool -- a feeler gauge. To check his work, I followed up with my dial indicator and found they were all off by a significant amount (more than 0.001 in). So, I feel somewhat validated in my reasons for doing it this way. But I'm interested in counterpoints, if there are any.

5axis · 03-28-2005, 01:43 PM

A B&S test indicator, the holder part of a indicol, a Starret flexible holder, and a few Kant twist clamps. I know exactly what my clearance is.

Tinker · 03-28-2005, 09:18 PM

5axis,

That looks great, but how would you fit that in there with the motor in the car?

Rotor,

I would suggest that you use both until you get comfortable with the correct "feel" for 0.10mm. That's how I learned on my first Porsche. Now I only use the dial indicator cam timing.

Tinker

rotorhead · 03-28-2005, 10:18 PM

Tinker,

I ended up doing as you suggested and I eventually managed to consistantly get between 0.8 and 0.13mm using the feeler. I figured that I needed to develop the right technique for the next valve adjustment.

Steve

2.7RACER · 03-28-2005, 10:46 PM

Using a .004" feeler gauge for the initial setting and then checking with a .003" and a .005" will tell you how close you are. Another way I use is to check between the cam and the rocker. If a .003" slides in the adjustment is loose. If you can't slide a .002" between the cam and rocker the adjustment is too tight. The rocker ratio dictates that .004" at the elephant foot equals about .0028" at the cam/rocker. The problem is once you have the .004" at the elephant foot it is very difficult if not impossible to re-insert the .004" feeler. The nice thing about checking between the cam and rocker is the feeler is somewhat guided into place. A dial indicator is great, providing you have the engine out and you have the dial locked down tight (no movement). Of course the dial indicator needs resolution so that .004" is easy to see. The indicator I use is one complete turn is .025". The .100" dials can be tough to read. Good Luck!

hcoles · 03-29-2005, 05:16 AM

Good info. on using the cam to rocker pad measurement as a check, makes sense and as you say there is guidance to get the feeler in.
-h

safe · safe's Garage

I just adjusted my valves for the first time. Becourse I'm doing my cam timing I have an dial guage at home and when I checked I had 0.12 mm. If you have 0.1 mm gap, you are not getting that feeler in again... Pretty tight.

hcoles · 03-29-2005, 06:13 AM

That's my experience. If you have .1mm very hard to get it back in, just have too feel that it is correct and then wiggle it out and that's it.
-h

Rob 930 · 03-29-2005, 10:44 AM

I see discussion about using a dial indicator to "calibrate" your technique with a feeler gauge. Why not just dispense with the feeler gauge and go with the dial indicator? I suppose there's a small expense associated with getting a dial indicator, but if you're doing any sort of engine work, they're either necessary (for valve timing) or handy for a variety of uses, and they make a good investment. You can get usable instruments with the correct resolution for less than $10 from places like Enco, and reasonably good ones for $30. You can make a holder, or perhaps buy a Z block (for cam timing) if you don't have one for about $30. And I'm easily able to use a dial indicator for adjusting valves in the car, no matter how much smog, AC stuff, or turbo hardware is attached. Well, "easily" might be a stretch, but just as easily as with a feeler gauge. It strikes me that a feeler gauge is such an inaccurate way to do this, and it's not any faster than using a dial. Why compromise?

safe · safe's Garage

A Z block workes fine. If you can fit a dial guage with the engine in the car I would use it. I have heard that many shops uses it instead of the feeler.