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with Larry Harris
Adjusting Valve Lash On The 8 Valve Engine
This is the first of a series from the factory service manual on how to
take care of your Samurai. This information is adapted from the 87 version
but it does apply to all 8 valve engines.
 So what is under your hood? For many we do not worry about what is there
until it starts making an unusual noise or strands us on the trail. Don't
let this happen to you, be prepared and perform a bit of maintenance. As
some of our trucks near their twentieth birthday a weekend spent with a
wrench in hand will go a long way to ensuing a great trail ride.
The stock Suzuki engine is a water cooled in line 4 cylinder, 4 stroke
cycle gasoline unit with a single overhead camshaft valve mechanism arranged
for a "V" type valve configuration. The camshaft is mounted over the
cylinder head; it is driven from the crankshaft through the timing belt,
no pushrods or hydraulics are provided in the valve train system.
 The cylinder head is made of cast aluminum alloy had has four combustion
chambers arranged in line. Each combustion chamber has an intake and exhaust
port. The camshaft has eight cams, and each cam operates the intake or
exhaust valve through a rocker arm. The valve lash can be adjusted by
turning the adjusting screw on the rocker arm after loosing the lock nut.
So what does all this mean? It is mechanical, it is old and If you do not
take care of it breakage will happen at an inopportune time. The good news
is inspecting and adjusting the valve train is easy.
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1 - Exhaust valve. 2 - Intake valve.
3 - Rocker arms.
4 - Camshaft |
Why adjust lash? To little clearance between the rocker
arm adjuster and the valve the valve would never close Especially true
when the engine warms up. This would cause a terrible loss of horsepower
and a poor running engine. It will in the long run cause mechanical
failure in burnt valves. To much lash (clearance) and we will have noisy
operation and low horsepower, the valves will not open enough to allow
the proper air and fuel charge into the cylinder.
The factory manual tells us to loosen the adjusting
screw locknut make an adjustment by turning the adjusting screw. After
adjustment tighten the nut to specified torque while holding the
adjusting screw stationary with a straight headed screwdriver, and make
sure to recheck the that the gap is within specification. Sounds easy?
What Is Lash And How
Is It Adjusted?
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Valve Lash or clearance is nothing more then the gap between
the rocker arm adjusting screw and the valve stem. A
thickness gauge is used to measure this gap at
"A"
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The Nuts And Bolts Of The "How To"
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Stop by your favorite online Suzuki Parts supplier and
get the required parts for the job at hand. You will also need a
basic hand tool kit.
This is a real good time to change the distributor cap
and rotor. |
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Valve cover gasket kit.
Make sure to get the kit that comes with
the seals that are on top of the valve cover. |
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| Remove the cylinder head cover. It may be
necessary to loosen the distributor to clear the vacuum advance when
lifting the cover off the engine. There are four bolts on the top that
thread through the cover in to the head. Do not pry on the valve cover
to remove it. A tap of a rubber mallet will break the seal. |
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| Standing on the drivers side look at where
the engine and transmission come together, remove the ignition timing
check window cover from the clutch housing of the transmission. It is
that little dirty rubber plug. |
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| Turn the crankshaft clockwise when viewing
from the front of the truck. Align the "T" on the flywheel with the
notch on the transmission case. This puts the number one piston at Top
Dead Center (TDC). You may have to clean the flywheel off at the
timing marks. Once clean use a bit of chock to highlight the markings.
This will come in handy when you set your timing. |
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| Remove the distributor cap and check that
the rotor is positioned as shown. It is pointing to the number one plug
wire, If the rotor is out of place turn the crankshaft clockwise
one full turn, 360 degrees. With the engine aligned in this position
check and adjust valve lash at valves 1, 2, 5, and 7. Rotate the
crankshaft one turn, and check the valves number 3, 4, 6 and 8. I find
it helpful to mark the valves with a dab of grease as they are adjusted.
If you look at the rocker arm and cam you will see the arm is riding on
the "Heel" or low section of the cam. |
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| The valves are numbered from the front to
back starting on the passenger side. Intake valves are on your left and
exhaust are on the right when looking from the front of the engine to
the rear.
So number 1 is the first intake valve on the passenger side closest
to the front of the truck. The number 5 is the first exhaust valve on
the drivers side closest to the front of the truck. |
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| The Most
Important Section It can take many years to learn the feel
and use of a thickness gauge. It is a judgment call on how tight or
loose the object measured really is. I have a better way to use this
tool, it takes all the "feel" out of the equation.
We are going to use the "go" - "no go" test. With this method anyone
can adjust valves.
Here is how it works. On a cold engine our adjustment range on the
intake valve is 0.13mm - 0.17mm, select a number in the middle of this
range. In this example we will go with 15mm. Now for the "go" - "no go".
On the thickness gauge pick one number higher and one number lower on
the then the desired value of 15mm. In our case this will be 14mm and
16mm. Isn't it great we do all the math for you ;-) |
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| How To
Adjust Using a 12 mm wrench on the lock nut and a flat
blade screwdriver loosen the locknut on the number one intake valve.
Loosen the adjusting screw, Place the 14mm thickness gauge between the
valve and the adjusting screw, lightly tighten the adjustment screw
until it just touches the valve (thickness gauge). Now holding the
adjusting screw so it does not turn tighten the locknut.
Pull out the 14mm gauge and try to insert the 14mm and the 16mm
gauge. The 14mm should "go" and the "16" should "no go". At this point
you can use the 15mm selected as our desired measurement and see how it
fits or "Feels" it should have a slight drag as it is moved in and out
between the valve and the rocker arm adjusting screw.
Mark the valve as complete with a dab of grease and move on to the
other valves in the first turn.
Complete this sequence on all valves. Rotate the crank as in the
instructions above and complete the remaining valves. |
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| Install a new valve cover gasket and bolt
seals, install valve cover, do not over tighten the valve cover bolts!
Set the timing, lock down the distributor bolt, close the hood and take a
test drive ;-) |
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