Easy Valve Adjustment Trick
Veeduber
Align pulley to TDC.
Adjust all valves that are loose.
Rotate engine one revolution and align to TDC.
Adjust all valves that are loose.
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Actually, it's not a 'trick' at all. It's the standard valve adjustment
procedure for all Otto-cycle four cylinder engines that have adjustable
poppet-type valves.
The reason it is the standard procedure is because it's based on the
Otto-cycle's 2:1 relationship between the crank and the cam, plus the fact
valve clearance may be adjusted any time the cam-follower is riding on the heel
of the cam lobe.
The usual procedure is to position the vehicle so you may work under the engine
then align the pulley to TDC, go under the engine, remove the valve cover,
adjust any loose valves, slide over to the opposite bank, remove the valve
cover, adjust any loose valves. If you're working alone you then climb out
from under, rotate the engine one full turn, go under the engine, adjust any
loose valves and replace the valve cover, slide over to the opposite bank and
do the same. All done.
Working alone, at my normal pace (kinda slow), it takes about 15 minutes. But
I usually do the valves in conjunction with other work, such as an oil change.
At a guess, it probably adds ten minutes to the job.
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Keep in mind this is a MAINTENANCE procedure. The engine is operating
normally. Stretched valves or worn adjusters are not addressed. Nor is this
method appropriate when assembling an engine.
'Loose' means some lash is evident; the valve rocks easily with finger
pressure. That means the cam-follower is riding somewhere on the heel of the
cam lobe. And that means you may adjust the lash. Rotating the engine one
full turn rotates the cam one-half turn. Any valve that was tight before will
now be loose and may be adjusted. Which particular TDC you happen to be on is
immaterial.
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I recently mentioned this method in passing, relative to another subject. I've
since recieved three requests to describe the method. I've posted the
information before, as have others, but a quick Google failed to produce a
reference, meaning I probably posted it to one of several VW-specific mailing
lists which are not archived by Google. So here it is again. Enjoy.
-Bob Hoover
Joey Tribiani
>I've posted the
>information before, as have others, but a quick Google failed to produce a
>reference, meaning I probably posted it to one of several VW-specific mailing
>lists which are not archived by Google. So here it is again. Enjoy.
>
>-Bob Hoover
thanks for posting bob....simple valve adjustments seem to trouble
most people when they first obtain an old vw...it is a foreign
procedure to them....i use your method, yet it is kinda hard to
explain to others how it works, so i usually use the standard "find
tdc of number one, then follow the firing order"....now we have a post
to point them to...thanks again Bob...
Joey
Max
I adjust my valves without using a feeler gauge.
For a given thread pitch the adjustor movement in & out will be
a linear function of the adjustor rotation. So, if you know how
many degrees to turn for .006", you can just run the adjuster in
till there is zero lash, then back it out the correct amount.
Finding out how much to back it out is simple. Just observe the
adjuster position when the lash is zero. Now back it out and
insert your .006 feeler gauge. Run the adjuster in till it contacts
the feeler gauge and observe the adjuster position. The difference
in adjuster position with and without the gauge is equivalent to .006".
For my Berg swivel-foot adjusters, this turns out to be alomost exactly 45º.
Note that this works better when the adjusters take a hex-wrench instead
of a flat screw-driver. Easier to see the rotation amount.
Max
Veeduber
Good for you :-)
Using thread-pitch to either set or measure a distance is a standard procedure
used by mechanics and machinists. It usually appears as instructions saying
something like: 'Tighten the axle nut (for example) to remove all lash then
loosen for one-eighth of a turn.'
This method works perfectly well for setting your valve lash.... IF (you knew
that was coming, right? :-) IF... you know the contacting surfaces are 'true,'
meaning something other than an edge or a groove or whatever.
Flat is good. With the Berg swivel-foot adapters you have a flat-to-flat
interface between the adjuster and the stem of the valve. Thread pitch may be
used to set the lash. For a 1.0mm thread pitch the adjustment would be about
54 degrees of rotation for a lash of 0.15mm. All of which means 45 degrees
would work just fine.
Unfortunately.... (the other side of the IF coin :-) Unfortunately, the
camber-faced adjuster screws used by Volkswagen become faceted in use -- they
wear FLAT at the point of contact. This leads to two potential sources of
error that makes it risky to use the thread-pitch method. The first problem is
that when you tighten the adjuster in order to remove all lash, in preparation
for backing it off a certain number of degrees of rotation, the point of
contact is often on the EDGE of one of those flat facets. And the top of the
valve stem MAY have a matching groove. Rotating the adjuster screw the
required amount to give you six thou of clearance from that point of contact
brings a DIFFERENT portion of the face of the adjuster screw into position....
and if you do not know the SHAPE of that new portion of the adjuster screw's
face, there's no way to be sure what the resulting distance will be.
Is it close enough to work? Yes. The engine will run; you can make it to
beach. But if you check it with a feeler gauge the odds are it will NOT be six
thou.
Is the error significant? It can be, if the lash comes out too tight. But in
most cases the only significance is that the valves, or at least some of them,
seem to go out of adjustment very quickly, as if the point of contact was
edge-to-edge instead of cambered-to-flat.
And if that sounds familiar, it should.
The stock adjuster screws are meant to be replaced when their face becomes
faceted. No one does, of course. (Too much trouble, or something.)
-------------------------------------------------
The method Max has described works perfectly well... under certain conditions.
Indeed, it is the most common method used for setting valve lash. But if the
adjuster screw and the valve stem are not in good condition this method gives
only an approximate amount of clearance.
Now here's the funny part :-)
Non-mechanics blame the improper clearance on the method of adjustment, rather
than on the condition of the adjuster and valve stem. So Conventional Wisdom
insists the thread-pitch method is 'no good' and go back to their feeler
gauges.
---------------------------------------------------
The thread-pitch method is perfectly valid and I recommend using it. But only
if your adjuster-screws and valve stems are in good shape. Ideally, you should
consider replacing your stock adjuster screws with a set of Gene's swivel-foot
adjusters... or the Ford/Subaru adjuster, if you're familiar with the
modifications required. (Gene's adjusters are pretty much a bolt-up; the
Ford/Soobie adjusters are not.)
Best of all, once you have a flat-to-flat interface you will find your valves
need adjusting only once or twice a year, since the larger contacting surfaces
wear at a much slower rate.
-Bob Hoover
PS - In case you were wonder just how accuate thread-pitch adjustments can be,
thread-pitch is the principle used in micrometers and other precision measuring
instruments.
-----------------------------------------------------
Max
> consider replacing your stock adjuster screws with a set of Gene's swivel-foot
> adjusters... or the Ford/Subaru adjuster, if you're familiar with the
> modifications required. (Gene's adjusters are pretty much a bolt-up; the
> Ford/Soobie adjusters are not.)
BTW, I've been told that the swivels that GBE ships today are the slotted type,
not the hex-wrench type. An issue with the supplier, apparently. :-\
Max
Max
> need adjusting only once or twice a year, since the larger contacting surfaces
> wear at a much slower rate.
>
> -Bob Hoover
.. unless you are incubating a valve seat, stem or pushrod issue. Keeping a
valve-lash log is a good way to spot trends.
Max
Scott H.
If anyone needs a visual reference, VW Trends has a webpage that describes
this procedure and includes some photos:
http://vwtrendsweb.com/tech/0106vwt_valve/
--
Scott
Dennis Wik
href="http://community.webtv.net/weewiktype1/Dens1978Puma">Den's 1978
Puma</a>
Tom Nakashima
VW mechanic. He claims that you can go down to .0005" -.002" on the
clearance for the valves???
-tom
"Max" <max_we...@yahoo.com> wrote in message news:1103_1053126177@max...
Joey Tribiani
<t...@slac.stanford.edu> wrote:
>Recently I got into a discussion about valve adjustment with a long time
>VW mechanic. He claims that you can go down to .0005" -.002" on the
>clearance for the valves???
>-tom
sure you can!!! i wouldn't recommend it if you have factory alluminum
pushrods though...with chromoly those are typical valve lash
numbers...
Joey
John Willis
scribbled this interesting note:
It is kind of interesting. In my various books and other printed
sources I find numbers that range from .004 to .008 as the recommended
valve lash alters with the various engines and years...
--
John Willis
Jan Andersson
And when you build high power street or especially race engines..
there's even more variety...
The race engines I am most familiar with (I help build them) commonly
use even .02 gaps... and no that's not a typo.
Jan