The Cap'n's valve adjustment procedure, Jim T and Cap'n Krusty's bestest way! Options

[Cap'n Krusty]

Here we go! Somebody hold my beer! The Cap'n, with thanks to Jim Thorusen, DDD, and others.

First, general rules:

Be sure that you use the correct clearance values for
your engine: .006 INTAKE... .008 EXHAUST (for 2.0 liter)
( .006 BOTH for 1.7 liter). SOME 1.8s that were rebuilt in
the '70s and '80s MAY have sodium filled exhaust valves
fitted and would use the .008" setting!

Don't mix them up! As a general rule of thumb, exhaust
valves run hotter than intake valves, therefore they lengthen
more due to expansion, therefore the larger clearance
specification will be for the exhaust valve. I'm sure that
someone can site an example of it being the other way
around, and of course there are engines (including the
914 1.7 litre) that have identical clearances for both, but as I
said, it's a rule of thumb.

If you set a valve .001" looser than spec, it might be a bit
noisier, but you will not harm anything. Setting an exhaust
valve .002" too tight will risk burning it... not a good idea,
so to reiterate: .006" INTAKE .008" EXHAUST.

Now, if you exert sufficient force on a feeler gauge, for
anything but big gnarly racing engines you can actually open
the valve with the gauge, as you have considerable
mechanical advantage owing to the curved shape of the
end of the rockers. A correctly adjusted valve will put a slight
amount of drag on the feeler gauge as it is moved back and forth.
If the gauge slips in with no resistance at all, the valve is too
loose.
If you have to strain, and the feeler gauge feels like it wants to
sproing into an inchworm shape instead of going in, the
valve is too tight. There should be just a little bit of drag on
the gauge; enough so that you can detect a friction effect,
even with oil present.
Once you have this feel in mind, stick in the appropriate
gauge and measure the clearance... as in fortran, you have
three choices: < > or =.
Once you have determined which way you need to go,
loosen the lock nut, turn the screw a bit in the correct
direction, and re-tighten the lock nut. Note that when
you tighten the lock nut, the adjusting screw sets back
into the rocker arm, commonly by as much as .001", so
allow for this when tightening, and let the adjusting screw
turn SLIGHTLY clockwise with the lock-nut. Repeat the
adjustment as necessary until the clearance is correct;
i.e. slight drag on the feeler gauge with ALL TOOLS OFF
THE VALVE TRAIN! There should never be any tool on the
rocker assembly, either screwdriver or wrench, while actually
measuring the clearance. You will introduce side loads or
other moments that will prevent an accurate measurement.

Now for the actual adjustment procedure. To understand
it, however, a bit of history and theory first.

I should like to point out that the 914-4 engine is a derivative
of the good old VW engine designed by Dr. Porsche way
back when. As the "people's car" everything, including the
engine, was designed for cheap mass production. As part
of this philosophy, Dr. Porsche reasoned (I take license here)
something like this: "Why should I design a typical 4-cylinder
engine camshaft with 8 lobes, when I can get by with half
that number?" Due to the flat-four layout, each cam
lobe does double duty, actuating a valve first on one side of
the engine, and then on the other.

This then gives rise to a simplified adjustment procedure,
which I have printed up and glued into my Haynes manual
to replace the rather cumbersome procedure in the book.

It works perfectly. I quote verbatim:

1. Jack up car and place on stands; block one rear road
wheel to prevent it's turning, engage 5th gear, handbrake off.

2. Valve clearances are adjusted with the engine COLD.
Clearances are INTAKE = .006" EXHAUST = 008". ('74
model year, 2.0 litre engine) Remove valve covers, clean
up spilled oil, and check gaskets; renew if necessary.

3A. Using the unblocked road wheel as a hand wheel,
rotate the engine until the rockers are rocking in accordance
with the first entry in the table below. Adjust the clearances
of the corresponding valves as shown in the table. Continue
rotating engine and adjusting valves until all have been
done. Re-install valve covers.

3B.As an alternative, a momentary starter button connected
between the starter post and the activation terminal may be used.
BE SURE the car is out of gear if using this method!

4. Valve adjustment table: # denotes cylinder number;
Ex = Exhaust valve; In = Intake valve.

Turn until Rocking: Adjust:

#2 Ex & #3 In #4 Ex & #1 In
#1 Ex & #2 In #3 Ex & #4 In
#4 Ex & #1 In #2 Ex & #3 In
#3 Ex & #4 In #1 Ex & #2 In




It follows logically that a valve opposite one that is open is
on the back of the same cam lobe, the perfect place for
adjustment. It is only necessary to be certain of which
valves actually share the same cam lobe, which can be a
little tricky owing to the offset nature of the cylinder layout.
However, I believe that I have done this, and that
further, I have worked it out so that, if the valves are
adjusted in the order given in the table, a minimum amount
of engine rotation will be necessary to complete the task.

One other helpful hint: Unless you are VERY familiar with
the engine layout, clean two spots on the bottom of each head
next to the pair of valves associated with each cylinder
and mark the cylinder number in the cleaned spots with
magic marker so that it can be seen from under the car.
This will help you figure out which cylinder is which while
you are upside down under the car, and is an invaluable aid
in using the table. The cylinder layout can be taken
from fig. 3.3 on page 63 of the Haynes book, or, if the
engine is clean enough, can be taken from stamped
numbers in the engine sheet metal.


Good Luck,
Jim T.

__________________

*********************************

The following is a reply to some folks who had trouble understanding what I
meant when I used the term "rocking"..... They wrote back to tell me that
the job went easily after this clarification.

__________________

Hello, Gene & Tony!

You wrote:

<snip>

" My son and I just bought a 1973 914 1700 and did our first valve
adjustment
on it today--it didn't talke us too long but it would have been a real bear
with just one person. We're NOT totally new to this type of motor--my son
drives a 1973 1700 VW Campmobile--and also not new to the valve adjustment
scene.

However I was quite intrigued by your approach and would love to try it,
but I can't figure out a few things. I hope I my questions aren't too
obtuse. Here goes:

I'm assuming one can adjust the valves BY HIMSELF without paying attention
to timing marks or top dead center, etc., by using the 'rocking' technique,
i.e. "

Yes.... it is a one-person job if you do it this way.... and further,
when you get to be as old and as fat as I am, you will appreciate the fact
that you don't have to get up off your creeper until you're finished. :-)

<snip>

" What does this mean--Rocking--and how to you know when you're in a
position
to do the first set of adjustments, which is:

"#2 Ex & #3 In #4 Ex & #1 In" "


Well.... not quite. I see by your enclosure that the table of
adjustments was distorted by the time you got it... I have reproduced it
with the spaces that need to be in it below:

Turn until Rocking: Adjust:

#2 Ex & #3 In #4 Ex & #1 In
#1 Ex & #2 In #3 Ex & #4 In
#4 Ex & #1 In #2 Ex & #3 In
#3 Ex & #4 In #1 Ex & #2 In


First, a definition of the term "rocking". The name that is usually
applied to the levers that convert the direction of travel of the pushrod
(out) to valve motion (in) is "rocker arms". Therefore, by definition,
rocker arms "rock", or pivot about the "rocker shaft", the gizmo that they
are mounted on. So "rocking" is observed movement of the rocker arm for
the valves mentioned in the first column of the table.
Once you have the PAIR of valves in the FIRST column of the table open
(rocker arms rocking, rather than in valve closed position) it is then
correct to adjust the CORRESPONDING PAIR of valves in the SECOND column of
the table (on the same line, or row of the table).

In other words, you would rotate the engine (by turning the
road wheel with the car in gear) until the # 2 exhaust and
the # 3 intake valves were observed to open (observed
motion of their rockers). When you have both of these
valves open, you can then proceed to adjust # 4 exhaust
and # 1 intake. This completes the first line of the table,
and you have two valves adjusted. You then proceed to
the next line of the table, and look for motion of the "que"
or "indicator" valves in the first column, and adjust the
valves in the second column. This process continues
until you have completed all four lines in the table,
adjusting two valves per line.


" ,,,now I'm again assuming what this means is that when you get the
valves
in the position above, you can adjust these four valves:

#2 exhaust, #3 intake, #4 exhaust, and #1 intake--right? "

No, only two at a time; see above.


<snip>


" So, please enlighten me on where I"m having difficulty understanding,
and
definitely tell me how to recognize when I"ve 'rocked' right to begin the
adjustments. Oh, BTW (by the way), as I'm looking at the #1 and #2 side of
the valve rockers, underneath the car, with #1 being to the left, which is
the intake valve, the 1st or the 2nd? "


The cylinder layout is pictured on page 63 of the Haynes book; fig. 3.3.
The intake valves are the pair in the center of the heads; the exhaust
valves are the outermost valves. The engine layout is such that the valve
layout for the LEFT side of the car is as follows (from front to rear):

# 2 Ex # 2 In # 1 In # 1 Ex

and on the RIGHT side of the car, from front to rear:

# 4 Ex # 4 In # 3 In # 3 Ex


I have taken the liberty of adding some theory on the mechanical layout
of the flat-four, and why this method works. This was posted to the list
to answer some questions similar to yours. I hope it helps.

From my files:

It is necessary to use the table of valves that I include; note
that in NO case are the two valves that are rocking at the same time
associated with the same cylinder.

Turn until Rocking: Adjust:

#2 Ex & #3 In #4 Ex & #1 In
#1 Ex & #2 In #3 Ex & #4 In
#4 Ex & #1 In #2 Ex & #3 In
#3 Ex & #4 In #1 Ex & #2 In


The reason was detailed in the complete procedure that I posted,
but perhaps it was not clear. Given that the best place to adjust
valve clearance is when the lifter (follower, tappet, whatever you
prefer) is on the BACK or circular part of the cam lobe, i.e.
opposite to the bump, then the problem simply becomes one of
positioning the cam so that it's back side is adjacent to the lifter
of the valve that we wish to adjust. Because of the valve train
layout of the flat-four, this is most easily done.
If you have a Haynes book, look at the illustration on page 26.
Near the bottom of the page is a pretty good picture of the 914 cam
shaft. Count the lobes. You will observe that there are only
four... but the engine has eight valves! The VW flat four is the
only engine that I know of to use this unique layout. The camshaft
has two exhaust lobes, and two intake lobes. Each lobe actuates two
valves on opposite sides of the engine; thus we can operate 8 valves
with only 4 cam lobes.
However, this brings up an interesting observation: If a
particular exhaust valve, for example, on the right side of the
engine is open, then it must be that the opposite exhaust valve is
fully closed; i.e. it's lifter is on the exact opposite side of the
cam lobe from the "bump". Referring back to our "given" above, this
is the perfect place to adjust the valve OPPOSITE to the one that is
open.
If you look at figure 3.3 on page 63 of the Haynes book, you will
see the engine cylinder layout.

The first entry in my table says: turn until rocking - # 2 exhaust
and # 3 intake. If you look at the engine layout, you will note that
the exhaust valve for # 4 is opposite to # 2 (the one that is open),
and likewise the intake for # 1 is opposite to # 3 (the open intake
valve). Therefore, at this point, we should logically adjust # 4
exhaust and # 1 intake, and referring to the table, that's exactly
what it says.

The rest of the table was derived simply by turning the engine in
it's normal direction of rotation and observing which valve pairs
rocked together next, and then noting their opposites to be adjusted.

Regards,
Jim T.

_____________________

*************************************************

The following is part of a discussion that Dave Darling and I had on this
method eons ago. I'm sure that you recall that this argument surfaced
again recently. I do not recall exactly who I had the discussion with, and
the thread is long gone due to a virus attack. The last thing I posted was
a set of quotes from various shop manuals illustrating the use of the back
of the cam for valve adjustment. The individual wrote back that the
examples I used (Alfa Romeo, MGA Twincam, and MGB were not relevant,
because they were high-performance engines, or some such silly reason. It was
obvious from the reply that the individual involved was weak in his
understanding of geometry, the list in general was begging that the thread
be allowed to die, and I got hit with two viruses the next day, so I just let
it pass. The following is Dave's experience, which is a bit more
relevant, I believe, and my reply to him.

____________________________


For Dave D.; cc porscheFans-914

Dave writes:

> I feel compelled to point out here that Jim and I disagree
> a bit about valve adjusting procedures.
> On my 2.0 motor, shortly before its rebuild, I measured the
> valve clearance on an exhaust valve while the intake valve on that
> same cylinder was open. It was larger than it should have been.

I just want to be sure that we are in agreement as to what my
procedure calls for; the valve that would be rocking in the case you
mention would not be the intake valve of the same cylinder, but the
EXHAUST valve of the OPPOSITE cylinder.

> Then I rotated the engine until that cylinder was at TDC--both
> valves were closed, and the fan mark was either at top or bottom (I
> forget which cylinder). The measurement was on spec.
> When I asked, I got two replies (Stan Hanks and AA's George
> Hussey) that indicated that the geometry of the valve train could
> increase the valve clearance at some points along the camshaft's
> rotation.

I would like a more detailed explanation of how this could be... a
camshaft lobe consists of two geometrical figures (in simplified
terms): a circle, and a triangle. For most of it's rotation
(assuming that the camshaft is in good shape) the follower is riding
on the circle, and the valve train geometry is static... the only
change that could result in a clearance change is the degree of
out-of-roundness or roughness of the cam itself.*** For the rest
of the rotation, of course, the triangular-shaped portion of the cam
drives the valve open.
The more radical the cam, the more the "triangle" departs from
that shape, and the smaller the arc on the back of the cam that
remains circular. For this reason, to avoid having to take into
account cam grind parameters, the standard place to measure valve
clearance is on the part of the cam EXACTLY opposite to the peak of
the lobe.
In a DOHC engine this is easy to do, since you are looking right
at the cams with the valve cover off, and you can rotate the engine
until the cam lobe points straight away from the valve. In a pushrod
engine, where the cam is invisible, some other method must be
employed to ensure that you are on the back of the lobe. The
infallible method (as well as the most tedious) is to rotate the
engine until the valve that you wish to adjust is at the point of
maximum opening. Then mark the flywheel (or fan, maybe in the case
of the 914) and rotate the engine exactly one revolution. At this
point, you will be exactly on the back of the lobe, and the
adjustment can be made.

Needless to say, this is extremely time consuming, and except in
the case of the most radical grind cams, is not necessary. The
procedures for valve adjustment for an MGB, an Isuzu, and a Nissan
all call for adjusting certain valves with certain other valves
rocking. This can be done because the manufacturer knows how far
around the cam the circular part extends, and thus how far off from
the exact back of the lobe adjustment is permissible. Also, it is
true that it is possible to come very close to the exact back of the
lobe for some valves with some other valves rocking, simply owing to
the nature of the valve timing for a particular engine.

In the case of the flat-four, we have a unique valve layout that
readily allows us to find the point opposite to the peak of the lobe.
This is because the same cam lobe operates a valve first on one
side of the engine, and then on the other. For example, when the
exhaust valve on cylinder # 2 is open, the exhaust valve on cylinder
# 4 is as closed as it's going to get, because the tappets for both
valves are riding on the SAME cam lobe, 180 degrees apart. Hence,
whenever the exhaust valve on # 2 is open, the tappet for the exhaust
valve for # 4 is on the back of the cam lobe, where the adjustment
should be made. To save time and effort, it will be noted that when
the engine is rotated, there are four places in the rotation where
two valves are open at once. It is at these four places that the
same type of valve (i.e. intake or exhaust) on the OPPOSITE cylinder
can be adjusted. The procedure that I have written up will enable
this to be done with a minimum of effort.

> I don't know if this was simply due to a wasted camshaft
> (it was replaced during the rebuild, and definitely needed it!)

This is the most likely cause.

> or if that really is normal.

Shouldn't be.

> However, I now always rotate my engine
> until the cylinder I am adjusting is at TDC, just in case.

Please note that although the relatively mild cam grind of the 914
makes this perfectly valid, you will not be as close to the back of
the lobe as you would be with my procedure; if you were running a
racing engine with an exotic cam, you might not be able to get
correct clearances this way.
In addition, finding TDC for all four cylinders requires special
marking of the flywheel as you have described; IMHO just observing
the valves is easier.


*** One other thing can cause erratic valve clearances, and that is
what I am suffering from in my engine. I have a mushroomed tappet,
that is very rough and irregular on the bottom. Since the tappet
rotates in it's bore in the engine case as the engine runs (normal,
all tappets should do this) it follows that the irregularities will
be juxtaposed with the cam surface in different ways at different
times. The result is that the valve clearance can change by values
in excess of .020"!! This condition makes the particular valve
involved (in my case, # 4 intake) practically impossible to adjust.
It is to be assumed that the cam itself is also probably damaged,
calling into question the adjustment of # 2 intake. As a result, I
typically run approximately .025" of inlet valve clearance on # 4,
which means that most of the time it clicks like crazy, but some of
the time it is right on.

However, I should like to point out that this or other departures
from design norms in the engine in no way invalidates the valve
adjustment procedure.