Tappet adjustment using thread pitch
 

Just had Oil lines replaced on a 88 Carrera and at the same time the engine was serviced. The Oil feed to the RH bank tensioner was replaced due to a slight oil leak. Following this the engine seems noisy at idle to around 1700 RPM) when warmed up (tapping/ticking sound) - it's great cold.
The car went back today and had the valve clearances checked - they use the pitch on the thread for the adjusting nut to 'gauge' the 4 thou clearance. They calibrated the turns required to give 4 thou.
Can anyone tell me how accurate this is - they do so many Porsche cars that I assume it is tried and tested? Also any clues as to why an engine would become noisy when warm following this work would be greatfully received.
Cheershttp://www.pelicanparts.com/support/...s/beerchug.gif

The elephant-foot adjuster has M8 x 1.00 mm threads ... so, one turn is one little millimeter. There isn't going to be much variation in thread pitch ... so for every 9° of adjuster turn you have approximately 0.001" of adjustment. Actually, 36° of rotation gives 0.0039" of travel, or the EXACT specified 0.1 mm of clearance!

Right on, Warren, Even though I don't do that myself, I know someone who routinely sets the valves that way: He snugs the adjuster down, then goes back one tenth of a turn (Since the pitch is 1.0 mm, the clearance will be 0.1 mm) He has done hundreds like that, so, I guess, experience counts.

That's probably good enough. I am told that the gap increases as the engine warms up. I like using a dial indicator when I check mine (they really do not get out of adjustment very fast) and when I do, only a couple are not correct. When I notice one is a thousanth or .0015 off, I make the adjustment. The distance I move the adjusting screw is what I would characterize as a "eentsy weentsy bit."

I've posted that method before...but got fairly slammed for doing so....

One can see 1/4 turn....cut that in half and you have 1/8 turn...either leave it athat or "smidge" it tighter slightly for 1/10 turn ( proper for 0.1 mm).

A related thread on "Tools" shows a clicker device that may do this "turn" thing for you ! don't know if it's available in metric !

Wil

Yep, the good thing about measuring (feeler or dial ind) is that you just have to check them . .. you don't have to reset/ re-gap each, and every one of the gaps.

I have tried the ~36° twist method.
I found that holding the screwdriver, while locking the lock-nut (without twisting the adjustment screw tighter) is the toughest part. Especially when you don't have something holding the gap. . . like a feeler gage.

So, You really have to watch the angle. . . which is not too hard to do on most of the rockers. (even w/o a tiny protractor ;) ) though some (top side) are a bit tough to see the proper twist-angle.

next thing you know, they'll come out with a valve adjust protractor. island??? i'll have to practice eyeballing 1/10th of a turn. should be easy back there on #6 intake.

Measure your cold adjustment with a feeler gauge, and tell us how accurate they were. It's theoretically accurate, and metric screw pitches are actually measured by the distance one rotation yields, as opposed to threads per inch. Still, I think JW is correct.

Years ago European Car featured a tool that worked on the angle principle. You turned it clockwise until the gap was closed and then turned it counterclockwise so many clicks to set the gap.
-Chris

Thanks for the feedback - the balanced view seems to be in theory it works - the practicality on some adjustments may be a little challenging!
As this method has been used and a ticking noise is now apparent when warm - should I assume further attention to the clearances is required or can there be another explanation associated with the renewal of the oil pipes, feeder pipe and filter?
Cheers

Track the ticking to it's location, like which side, intake, exhaust, etc. and then point it out to the mechanic.

You're funny, John.

36 degrees of rotation sounds fine, except that if one were to practice this, then it would be sort of like guessing. Guessing when you could, alternatively, KNOW. And Island is right, most times this method would probably just misadjust the gap since most of mine are correct when I check them. Just a couple need adjusting and when I'm done, I know for a fact they are all .004".

Superman....

So...you mean you miked the blade thickness? If not, you're in for a big surprise !

Wil ( my .004's miked within .0042 and .0046)

Good point. Even then, compare your guage finding average to several others as they can be off as well. Grease, dirt, angle, and other inconsistencys.

JW hit the nail on the head. Those mechanics who set your clearances with the 36 degree method; ask them for their certificate of calibration on their eyeballs. Make sure the cert is current and tracible to NIST, and make sure the calibration history is sufficient to warrant the calibration interval on which they are recalibrated. Tell them you would like to see the calibration history to see if any significant out of tolerance adjustment were made, and if so, see if the mechanic can tell you all the cars he has performed valve adjusts on, and make sure he has a recall system in place, so he can recall any vehicles he adjusted when the significant out of tolerance condition existed. At this point I would say that he could use this method for setting my valve clearances.
Nuff said.

The tool is the Gunson Click-Adjust. I've got one I use on my 1953 MG. It works well for larger gaps and for applications where the valve stem and rocker wear cause a feeler guage to give false readings. Clcik here for a description.

I thought about trying to use it on the 911, but the clicks are spaced too far apart to get an acurate .004 in. Also, the elephants foot on the 911 engine should minimize surface wear in the gap.

I decided to build something better than a calibrated eyeball using a worm gear drive 'interfaced' with a home-made digital counter.

Turning the knob on the left will turn the srewdriver blade very slowly while incremeting the LED display. When the counter reaches 72, the blade has turned 36 degrees. I haven't done an actual field test yet, but it seems like it should work if there is enough room to use it.


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