How to adjust valves on a chevy smallblock
There are a several methods for a valve adjustment on a chevy small block engine. Everyone seems to have a valve adjustment method they are most comfortable with and some of them will work well, but some are an inaccurate valve adjustment method. Even GM recommends doing the valve adjustment while the engine is running, which I won't teach you because it makes a tremendous mess.

You are going to learn how to do the valve adjustment, or more appropriately, adjust the lash or clearance between the rocker arms and the head of the valve stems using a method that will work for all 4 stroke internal combustion engines. The only difference between engine makes and models would be the details such as the number of turns after you have reached a zero lash, or in the case of solid lifters, the lash setting.

First consider that there is a relationship between the high position on each cam lobe for each cylinder respective of which stroke the cylinder happens to be in. We are going to adjust each valve at a time relative to the position of its peer valve ( or cam lobe ), either the intake or exhaust. This method insures the cam lobe for the valve you are adjusting is directly opposite the valve lifter and there is no measure of lift acting on the valve train components .

To do the valve adjustment you will need to crank the engine over in the same direction it would turn if it were running. If the engine is not in the vehicle you can turn the flywheel, or if it is in the vehicle you can use a remote starter button.

You will do the intake valve adjustment as the exhaust valve is just opening and you do the exhaust valve adjustment as the intake valve is almost closed. You might need to say that quite a few times to memorize it.

Here are step by step instructions:

Remove the valve cover.

Identify the number one cylinder. See the page on Firing Order on the menu to the right if you are not sure which cylinder is number one.

Turn the engine over until you see the number one cylinder exhaust valve rocker arm JUST START to move from the closed position to open. You may need to turn the motor over a couple of times to reach this point, but do not turn any further.

Locate the intake valve.

Loosen the rocker arm adjustment nut until you feel some obvious lash or clearance in the adjustment.

Using the thumb and index finger of one hand, grasp the intake push rod below the rocker arm, and rotate it back and forth (clock-wise and counter clock-wise successively to be sure there is no remaining pressure on the push rod from the rocker arm as you loosen the rocker arm adjusting nut.

Using the other hand, while continuously performing step 6, with a 5/8 socket and ratchet, tighten the rocker arm adjustment nut slowly until you feel a resistance of motion on the push rod.

This will be the zero lash adjustment point. For hydraulic lifters, tighten the rocker arm adjustment nut 3/4 of a turn. For solid lifters, back off the rocker arm adjustment nut until your feeler gauge just fits under the contact point between the valve stem and the rocker arm. Fine tune the adjustment by checking it with a feeler gauge just slightly thicker than the preferred clearance to be sure the clearance is not greater than it should be. If the larger feeler gauge will fit, it needs to be re-adjusted. A lash tolerance of 1-2 thousandths of an inch in the valve adjustment for solid lifters would be acceptable since it may be difficult for someone who is in-experienced to be more precise than that.

Turn the engine over until the intake valve opens and then is almost closed.

On the exhaust valve, repeat steps 5 through 8 for the exhaust valve adjustment.

Repeat this procedure for each cylinder. Be sure to do each cylinder sequentially, either following the firing order, following the cylinders numerically, or in the case of a V8 doing one side of the engine at a time. I prefer to do one side of the engine at a time.

This tech paper will discuss the adjustment of Chevrolet hydraulic lifters (“valve lash”).
The procedure outlined here differs slightly from the Service Manual, and is based on my years of
experience doing this work in the quickest, least painful, most economical way while keeping the level of
quality high. It is recognized that other people will have different methods of doing things, and may
disagree with specific methods and procedures that I use.
Overview, Theory and my Thoughts on Lash Settings
Hydraulic lifters are wonderful little innovations which reduce valve train wear and virtually eliminate
required valve train maintenance.
Without the use of hydraulic lifters (mechanical lifters), the valve train must be adjusted with a certain
amount of “slop” in it (“lash”). This lash is necessary, since the various components in the valve train tend
to “grow” and expand as they heat up from normal engine operation. As the components “grow,” they take
up a large portion of the lash, but some lash must still be retained as a safety margin. If there were no lash,
there would be a risk of the valves not closing fully, resulting in poor engine performance and burnt valves.
This lash, however, results in a bit of valve train noise as parts “clank” together, and this clanking induces
wear of the valvetrain components. This wear, in turn, requires that the lash be re-adjusted at regular
intervals. If only there were a way to eliminate the lash…. hmmmmm….
Enter the hydraulic lifter. Believe it or not, but the internal components of a hydraulic lifter are the most
precise, close-tolerance parts on a vehicle. The basic operation and principle of the hydraulic lifter is as
follows:
When the hydraulic lifter is at the “low” point in its bore (the valve is closed), the body of the lifter is
exposed to pressurized oil in the lifter oil galley. The lifter body has a little hole in it, and this hole allows
oil to enter and/or exit the lifter body. The pressurized oil in the galley thus enters the body of the lifter,
and pushes lightly on a plunger in the roof of the lifter body. This plunger is about a half inch in diameter,
giving it a total area of approximately 0.12 square inches. If you’re running 60 pounds of oil pressure, that
means that the oil is pushing upwards on the plunger with a force of about 11 pounds max. This 11 pound
force is not enough to open the valve, but it will remove all slack out of the valve train.
As soon as the lifter starts moving upwards in its bore (the cam is opening the valve), the oil hole in the
lifter body moves out of alignment with the oil galley. The lifter body is sealed off, and oil can’t get in or
out of the body. The lifter, thus, goes into “hydraulic lock,” and suddenly acts like a solid lifter. The oil
under the plunger is not compressible, so the lifter now opens the valve.
As the lifter comes down the bore after completing its valve opening chore, it is once again exposed to the
oil pressure in the lifter galley, and the pressurized oil once again assures that all lash is taken out of the
valvetrain before repeating the opening cycle. As the valvetrain wears, the oil pressure simply constantly
pushes the plunger upwards to remove any slack caused by the wear. The plunger can be pushed upwards
in the lifter bore within the design limitations of the lifter, and will eventually be stopped by a snap ring
retainer in the top of the lifter body. Once the plunger reaches the retainer, it can no longer provide
effective valve train adjustment, and the valvetrain will start making noise.
The distance the plunger is compressed into the lifter body when the lifter is at the low point in its bore is
referred to as “lifter preload.” This is the “valve lash” or “valve adjustment” on a hydraulic lifter. The
further the plunger is depressed, the more wear the lifter can “absorb” before reaching the snap ring
retainer. However, the more the plunger is depressed, the more prone the engine becomes to “lifter float”
or “valve float.”
As we noted earlier, the oil in the lifter is not compressible. If, somehow, the lifter body were filled with
just a few drops of oil too many, and the lifter were moving so fast in its bore that the oil did not have a
chance to bleed out and re-stabilize the valvetrain lash at the bottom of the lifter travel, the lifter would
keep the valve open when the valve should be closed. Further, if aggravated, this condition could cause the
lifter to open the valve beyond its design limitations, out of time with the intended valve cycle. This is
what is known as “lifter float” or “valve float.” It can have disastrous consequences if the valve were to
hit the piston. We, therefore, adjust hydraulic lifters with some pre-load, but not too much. So what’s the
right spec…?
Obviously, we can eliminate valve float completely by simply adjusting our lifter pre-load such that the
plunger is right at the top of the lifter body; right up against the snap ring retainer. The problem with this
approach is that there is the possibility of the same hydraulic lock conditions exerting so much force on the
snap ring that the snap ring is forced out. With nothing retaining the plunger, we would have the same
disastrous ending to our engine… Also, with no plunger travel available, the non-maintenance feature of
our hydraulic valvetrain is defeated, and we must now constantly adjust the valves as if they were
mechanical.
The factory setting on a Chevy lifter pre-load is ¾ to 1 turn lifter preload with the lifter on the low side of
the cam (valve closed). This eliminates valvetrain maintenance for at least 100,000 miles, and is a good
compromise setting. However, it can allow the valves to float at rpms as low as 5700. This, effectively,
becomes a factory-installed rev limiter: if they can make the valves float lightly around 6000 rpm, GM can
reduce warranty claims from customers over-revving their engines. Hey… these boys and girls designing
this stuff in Detroit aren’t dummies, are they?
So for a performance application, we split the difference. A ½ turn lifter pre-load will raise the rpm limit of
the engine, yet it will still provide quite a bit of plunger travel so the lifter can do its valvetrain wear
adjustment thing.. It will also keep the plunger away from the snap ring retainer, and it will keep our
operation safe. Safe, reliable, improved performance and good durability/life: what more could you ask
for?
Procedure
This procedure typically takes me about 30 minutes from start to finish on a Chevy without air
conditioning, but I’ve done it a few times. Allow yourself an hour or two for a leisurely pace of wrenching
and beer drinking.
General tips:
Keep your work area clean and organized. It’ll make the job seem much easier. I like to lay a clean towel
out on the ground by the car or on an adjacent workbench. As each bolt, screw, nut and component is
removed, I lay the parts out carefully on the towel. Whenever possible, I put screws back into the holes
that they came out of after the component is removed. Wipe up spills and sweep the area as you progress
to keep things clean and pleasant. You will be leaning across the fenders on pre-C4 cars, so use a fender
apron.
Step-by-Step:
·  Park the car on a level surface. Set the parking brake and block the tires. On manual cars, put the
trans in neutral. Pull the coil wire that goes from the distributor cap to the ignition coil (on HEI
cars, disconnect the connector out of the distributor) and ground it.
·  Turn the engine over until you can see the timing mark on the harmonic balancer. Using a piece
of chalk or other visible marker, place three more timing marks on the balancer: one mark every
90 degrees around the balancer (one exactly opposite the factory mark, and two in between these
marks: just get it pretty darned eye-ball close, it doesn’t have to be exact.)
·  Remove the valve covers. You may have to remove some accessory brackets in order to do this.
·  Rotate the engine over (either by “bumping” the starter or by inserting a socket and breaker bar
onto the harmonic balancer bolt) until the factory timing mark lines up with “0.” Observe the
pushrod for the exhaust valve on the #1 cylinder: if the pushrod moves as you come up on Top
Dead Center, you’re on the exhaust stroke, and you need to rotate the crank one more time. If
neither pushrod moves as you come up on the timing mark, you’re on the compression stroke and
ready to go.
·  Loosen the adjustment nuts on both the rocker arms for cylinder #1 using a deep socket and a ½”
drive ratchet. One at a time, adjust them as follows:
·  Place the pushrod between you thumb and forefinger of your left hand (or right hand if you’re left
handed…). Rotate, or “twirl,” the pushrod back and forth between your fingers and notice how
lightly and easily it spins. As you do this, slowly tighten the rocker arm nut. The instant you feel
the “twirl” friction change between your fingers, you are at “0” lash. STOP. Now, notice the
position of your ratchet handle. Tighten the nut exactly ½ turn from your current position. Do the
same to the other rocker arm for #1 (when doing this, make sure that the friction you feel as you
swirl the pushrod is not caused by your ratchet and socket pushing or binding on the rocker arm –
keep things straight and aligned, and watch for false indications caused by your tools). That’s it
for #1.
·  Now, here’s the trick:
What’s the firing order for a GM V8?
1-8-4-3-6-5-7-2
How often does a cylinder fire in a V8?
Every 90 degrees
That means we can now rotate the crankshaft 90 degrees at a time, and go right to the next
cylinder in the firing order for the valve adjustment, with confidence that both of the valves for
that cylinder will be closed and ready to adjust.. So rotate to your next chalk line, and adjust #8 as
described above. Rotate to the next line and adjust #4. After you’ve rotated the crankshaft twice
over (using the starter and “bumping” is the easiest way), you’ve finished your valve adjustment!
No oily mess, no worrying about if you missed a valve. Just a nice, simple, structured procedure!
·  Pop your valve covers back on with a fresh set of gaskets, re-install any accessory brackets you’ve
removed, and start it up with confidence. You now have a correctly adjusted valvetrain that will
operate quietly and with outstanding performance and reliability.:
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