(775) 746-4887

 Cart

Valve Adjustment Procedure

Valve Adjustment Procedure

Century Performance Center - Tech Zone:::: The CORRECT Way

We are regularly asked by people what the correct procedure is for adjusting the valve lash on their engine. It seems that everyone they have asked provides them with a different procedure. This article should make the correct procedure easy to understand for just about everyone.
Read this entire article to understand correct valve adjustment procedures for most engines.

Introduction to Adjusting Solid and Hydraulic Lifters:

The simplest way to adjust a hydraulic or solid lifter camshaft, whether it is a flat tappet or roller cam, is described below. But FIRST, you need to forget about all that information that many individuals (and books) have taught you in the past. In many cases, if interpreted wrong, you could be in for more trouble than before you tried to adjust the valves in the first place. Think about those things that can affect your valve lash, because you will need this bit of common sense before you get into this. There are other considerations besides just putting a wrench on something and attempting to follow the cam card, shop manual, or the advice of some friend or relative.
 
What type of cam are you running? (Hydraulic, Solid, Hydraulic Roller, Solid Roller, Mushroom Tappet)
  • Are you running aluminum heads?
  • Are ALL of your valvetrain parts in proper working condition?
  • Are your valve springs the correct size and tension for the camshaft and operating RPM?
  • What type of driving (or racing) are you going to be using the engine for?
  • Do you have the tools and basic knowledge required to adjust your own valves?
The last one above is quite important. If after you read through this and are still a bit confused, please ask for help or have someone else do it. In the very least you can have someone who is more knowledgeable walk you through the process to make sure you understand the procedure. If you are wondering what can go wrong, I have provided the short list below as to a few bad things that can occur:
  • Poor running engine and low performance
  • Failed smog test (if this is a smog-legal street driven vehicle)
  • Burnt exhaust valve(s)
  • Broken valvetrain components (springs, pushrods, lifters, camshaft)
  • Limited lifespan of valvetrain components
  • Excessive valve guide and valve seat wear
  • Blown up engine
  • Lose an important Race!
  • Empty or put a substantial dent in your bank account
The above list, though quite simple to understand, should scare you. It takes only a few thousandths of an inch (0.001") of adjustment error to cause any one or more of the problems listed above. Now we can get to the actual process. I am going to simplify this a bit, so if your valvetrain is somewhat different you will need to verify the correct procedure for your application.
 
Forum Redirect Request
 
IMPORTANT WARNING:
 
For those of you with Ford, and other engines with "Non-Adjustable" valvetrain ... YOU MUST verify that your machinist did their job correctly when setting the valve stem heights, and then YOU must also verify proper plunger depth when using Hydraulic Lifters. If you switch to solid lifters it is mandatory that you convert to an adjustable valvetrain (I would also say that converting to adjustable valvetrain is mandatory in ALL racing applications as well as any application where you want to have accurate control of your valve lash setting). Not doing so is asking for serious problems!

Valve Adjustment Procedure - The Quick and Accurate Way:

First, view this simple chart below for Small and Big Block Chevy Engines and see if you can understand it. There is more of an explanation below the chart. For other engines you will use the firing order that matches your engine to create a similar chart. This chart is based upon "opposite" cylinders of your firing order. (see below)
 
Intake Valve Adjustment: ENGINE OFF!
  • with #1 cylinder Intake Valve at full valve lift .... Adjust #6 Intake Valve
  • with #8 cylinder Intake Valve at full valve lift .... Adjust #5 Intake Valve
  • with #4 cylinder Intake Valve at full valve lift .... Adjust #7 Intake Valve
  • with #3 cylinder Intake Valve at full valve lift .... Adjust #2 Intake Valve
  • with #6 cylinder Intake Valve at full valve lift .... Adjust #1 Intake Valve
  • with #5 cylinder Intake Valve at full valve lift .... Adjust #8 Intake Valve
  • with #7 cylinder Intake Valve at full valve lift .... Adjust #4 Intake Valve
  • with #2 cylinder Intake Valve at full valve lift .... Adjust #3 Intake Valve
 
Exhaust Valve Adjustment: ENGINE OFF!
 
You will notice that this is the same procedure and sequence as the intake valves listed above. Only now you are adjusting ONLY the exhaust valves the same way.
  • with #1 cylinder Exhaust Valve at full valve lift .... Adjust #6 Exhaust Valve
  • with #8 cylinder Exhaust Valve at full valve lift .... Adjust #5 Exhaust Valve
  • with #4 cylinder Exhaust Valve at full valve lift .... Adjust #7 Exhaust Valve
  • with #3 cylinder Exhaust Valve at full valve lift .... Adjust #2 Exhaust Valve
  • with #6 cylinder Exhaust Valve at full valve lift .... Adjust #1 Exhaust Valve
  • with #5 cylinder Exhaust Valve at full valve lift .... Adjust #8 Exhaust Valve
  • with #7 cylinder Exhaust Valve at full valve lift .... Adjust #4 Exhaust Valve
  • with #2 cylinder Exhaust Valve at full valve lift .... Adjust #3 Exhaust Valve

 


Now I Will Provide an Explanation:

Camshaft Lobe Terminology
 
 
A few terminologies and words to understand their meaning throughout this article:
 
Full Lift - The valve is OPEN and the lifter will be on the nose (highest point) of the cam lobe.
TDC - Top Dead Center, or where the piston is at the top of the cylinder and both (all) valves for that cylinder are closed.
 
What you see above are adjustments being made on "opposite" valves on the engine rotation cycle. Small and big block Chevrolet engines use a firing order of 1-8-4-3-6-5-7-2. What you are going to do is separate the order into the two sides of the firing order. These are "exact" opposites that put the opposing valve at the correct location for adjustment, meaning the back side (base circle, or heal) of the cam lobe (see image at left).
 
Using the chart below (common Chevy V8 firing order described above) you will see that #1 is opposite #6, and vice-verse on the others through the firing order. This holds true for both intake and exhaust valves.
 
This procedure works on most V8 and V6 engines. The small chart below is showing you the opposite cylinders for a small or big block Chevy V8 engine with the above firing order. What this is showing you is a simple version of the above "opposite" list.
1 « - » 6
8 « - » 5
4 « - » 7
3 « - » 2
 


Lifter Position on Camshaft LobeIf the lifter is anywhere other than on the heal of the camshaft where there is NO ramp contact when you make your adjustments, you will have incorrect lash. This position is required for each valve before you attempt to perform adjustments. The chart and procedure above ensures that the lifter is on the backside of the cam lobe for each valve. When you were previously instructed by the auto shop teacher or service manual to position each cylinder at TDC (piston at Top Dead Center), then adjust both valves for that cylinder, you will often find this is not the correct procedure to obtain the proper lash setting. View the image at right and you can see the required position of the cam lobe to be able to correctly adjust the valve lash.

Roller Camshaft

 
You want to be sure that the lifter is positioned on the heel of the cam lobe which will guarantee that the valve you are adjusting is fully closed. Any other position and your adjustments will NOT be accurate.
 

What about the actual adjustment procedure?

Hydraulic Camshafts:
 
Let's get to the actual wrench turning. How many of you read or were taught that with a hydraulic lifter camshaft, you adjust it down to where there is slight pushrod resistance (zero lash) and then turn it down 3/4 or a full turn? Well, if you did this, you more than likely have opened the valves slightly, and they are now unable to close all the way!
 
Hydraulic Valve Lifter - Exploded ViewThe typical hydraulic lifter requires an adjustment that is roughly half the available travel of the plunger. If an average hydraulic lifter plunger has a range of 0.060" (sixty thousands of an inch) of travel from fully compressed to its static height where the pushrod seat is up against the retaining ring, half of that distance will be +/- 0.030" (thirty thousands of an inch). This means that you adjust valves by the depth that the plunger in the lifter drops. If adjusted too tight (the plunger fully compressed) the valves stay open slightly, and do not close all the way. This removes the important cooling time (lash) that whose entire purpose is to remove heat.
 
If the adjustment is too loose, the valvetrain will be loud, damage may occur to the valve tip (top of the valve stem), rocker arm, push rod, pushrod seat, the lifter, and camshaft lobes. How do you get to a 0.030" or centered plunger depth? On newly assembled engines I will actually use a dial indicator and measure the distance of travel on the new lifter. On an complete engine, especially one already in the car, this is a bit different and harder to do.
 
I have two procedures that I use to adjust hydraulic lifters. One uses the "clean" method with the engine turned off, and the other is the messy way with the engine running and squirting oil everywhere. To me, the messy way is always a last resort. Using custom cut-up valve covers, oil deflectors, and other techniques in an attempt to keep the oil in the engine and out of the engine compartment and off the ground can be an intense chore!
 
 


Engine "OFF" Hydraulic Lifter Adjustment:
 
If the engine is complete and installed in the vehicle you will need to warm up the engine by running it until it gets to operating temperature (15-minutes or so). Have all your tools ready and then quickly remove the valve cover(s) and start the adjustment procedure by using the chart above. With the #1 Intake valve at FULL LIFT. This means that you turn the engine by hand until the intake valve on the #1 cylinder is fully open (watch the rocker arm push down on the top of the valve stem, compressing the valve spring until it stops moving downward). You can now adjust the intake valve on "opposite in firing order" cylinder (see the above chart).
 
Remember, the opposite is engine firing order dependent. In this article I am using the small and big block Chevy engines as the example, so this would be the #6 cylinder. Loosen the rocker (if using roller rockers there is typically a Jam Nut that you must first loosen with an Allen Wrench). Now, with two fingers spinning the pushrod between them to feel for resistance you carefully snug the adjustment nut. When you feel resistance in the pushrod as it applies pressure to the socket in the rocker arm and lifter - STOP, now you will adjust the nut down "Only" 1/8-1/2 turn further. If you operate your engine a consistent high RPM, use the slightly lighter setting of (1/8 turn).
 
What is 1/4 turn? (see image below)
 
What a quarter turn meansThis is another area that has been taught wrong in auto shop classes and very expensive service manuals since the 1950's. Imagine the hands on a clock. You have the obvious 12:00, 3:00, 6:00, and 9:00 o'clock positions as well as the numbers in-between those points. If you start with your wrench at the 12:00 position and turn it clockwise to the 6:00 position you have just made 1/2 turn. Going from 12:00 to the 3:00 position would be 1/4 turn. Many manuals say to adjust the valves three quarters to one full turn ... THIS IS INCORRECT!!!!
 
Now, you will do this same procedure for all the intake valves and then do the exhaust valves the same way.
 
PRECAUTION: If you have an older high mileage engine on which the lifters bleed off pressure (drain the oil out of the lifter body), you can improperly adjust your valves. You need oil in the hydraulic lifter to be able to get an accurate setting. If you repeatedly attempt to adjust the valves by this procedure and they are still not correct, you probably have lifters bleeding off during adjustment. You have two options: Replace the Lifters = or = adjust the valves using the "HOT" running method described below. One way to tell if this is occurring (bleeding off or no oil) is watching the rocker when you are making your 1/4 to 1/2 turn of the wrench. If the rocker pushes the valve stem down instead of the pushrod, you are opening the valve instead of adjusting the lifter!
 

Engine RUNNING Hydraulic Lifter Adjustment:

So you really like messes? This has to be one of the most miserable maintenance procedures if you do not properly plan ahead.
 
Some helpful hints:
  • Adjust only one side of the engine at a time.
  • Use oil restrictors (deflectors) on the rocker arms, or better yet a butchered up old valve cover that has an access cut into the top of it to facilitate adjustment access.
  • Stay calm ... you WILL get burnt, you WILL make a mess and you WILL not look forward to doing this again, especially if you screw up the first time.
  • Using a mechanic's stethoscope can substantially make this procedure easier, especially if the engine is loud or you have hearing issues.
Adjusting hydraulic lifters with the engine running is not one of my favorite activities (as you can tell by how many times I mention it). With the above considerations addressed you are ready to go:
  • Start the engine and allow it to warm up.
  • Turn off the engine
  • Remove one valve cover and install your deflector clips, custom valve cover, or whatever apparatus you are using to keep the oil splash to a minimum.
  • Start the engine back up.
  • Begin to loosen one of the rocker arm adjusting nuts. You should hear the valvetrain just start to "clatter".
  • Slowly tighten the rocker nut down until the "clatter" just stops
  • Turn the wrench an additional 1/4 - 1/2 turn to set the plunger depth (lifter preload).
  • Continue (repeat) this procedure on each of the remaining the valves.
  • Turn off the engine
  • Remove your oil splash apparatus and re-install the valve cover
  • Repeat these steps on the other side of your engine (if a V8)
If you hear excessive noises or the engine runs rough and poorly you will be doing the procedure again. As stated above, if you have access to a mechanic's stethoscope, you can set the end at the top of the rocker stud to listen to the noise a loose adjustment makes, which will make finding "zero" lash easier.
 
IMPORTANT WARNING: If you make a mess, PLEASE use environmentally conscious methods to clean up any oil spills and then check your oil level. You would be surprised at how quickly, and how much oil can spill when performing valve adjustments with the engine running if you are not able to keep the oil in the engine!
 


Solid Lifter Adjustment:
 
First warm the engine to operating temperature (about 15-minutes) and then quickly remove both of the valve covers. Follow the chart above. With the #1 Intake valve at FULL LIFT. This means that you turn the engine by hand until the intake valve on the #1 cylinder is fully open (watch the rocker arm push down on the top of the valve stem, compressing the valve spring until it stops moving downward). You can now adjust the intake valve on "opposite in firing order" cylinder (see the above chart). Remember, the opposite is engine firing order dependent. In this article I am using the small and big block Chevy engines as the example, so this would be the #6 cylinder. Loosen the rocker slighly (if using roller rockers there is typically a Jam Nut that you must first loosen with an Allen Wrench).
 
Based upon your cam card (cam specifications provided by the camshaft manufacturer) you should know what the valve lash setting should be in thousandths of an inch. Let's say that your recommended valve lash setting is .022". Get out the .022" feeler gauge and place it between the top of the valve stem and the rocker arm tip. Snug down the rocker "just" until you begin to fell resistance. You should be sliding the feeler gauge back and forth gently on stock style slotted rocker arms, or gently side-to-side if using roller tip rockers. The valve lash setting should not be tight ... the feeling should be about the same as putting a table knife through a stick of cold butter. Not too hard, not too soft. Hopefully you are using "positive-lock" rocker arm retention fasteners instead of just cheap pinched rocker nuts or Nylox. If using rocker nuts your job is done, go to the next valve. If using positive-locks, hold the body of the lock in place with a box end or open end wrench (there are special tools available to simply this procedure if you want to spend the $$$ on them) and then tighten the Allen set screw in the center of the posi-lock.
 
NOTE: In most cases the Allen set screw will make a slight "click" when it is tight.
 


Compensating for a Cold Engine When Adjusting the Valve Lash

When installing a new camshaft, your engine will obviously be cold. The problem is that the provided lash specifications are for an engine that has been running long enough to be at normal operating temperatures. What are you to do? There is a standard correction factor that can be used to get you close to the required settings. You must now consider the material alloys of the engine parts, because the thermal expansion of these components affect the valve lash in different ways. Therefore the correction factor used for your lash setting will depend upon whether the cylinder heads and block are made out of cast iron or aluminum.
 
Take the "hot" setting provided to you in the cam manufacturer's catalog or from the cam card that came with your camshaft. Use the figures below to alter the original lash specifications to get a "cold" lash setting.
  • Using iron block and iron heads, add .002"
  • Using iron block and aluminum heads, subtract .006"
  • Using both aluminum block and heads, subtract .012"
Remember this correction adjustment is only approximation, and it is only meant to get you close for the initial start up of your engine After the engine has been properly warmed up to normal operating temperatures you must go back and reset all the valves to the specified "hot" valve lash settings.
 


Using Valve Lash to Help Tune Your Engine

This is a little extra tip that is still unknown to many engine builders and tuners. Most people do not realize that you can make subtle performance improvements by slightly opening or closing the recommended lash settings. This is for SOLID LIFTER camshafts ONLY!
 
The intake and exhaust valves cannot move until all the running clearance (valve lash) has been taken up. Therefore, the amount of valve lash you use affects the engine's performance. For example, if you decrease the amount of (hot) valve lash, the valve will open slightly sooner, provide slightly more lift (valve opening), and close later. This makes the camshaft look bigger to the engine, due to this slight increase of duration and lift. If you increase the amount of (hot) lash the opposite occurs. The valve will open later, provide slightly lift less, and close sooner. Now your engine sees a smaller cam with slightly less actual duration and lift. BE CAREFUL - I am suggesting you start with only 0.001 - 0.003" of change in lash. Crazy experimentation can destroy your engine! A timebomb waiting to explode.
 
You can use this tuning method to experiment, finding what the engine responds to, then keep the setting that works the best. Just remember, the more lash you run, the noisier the valve train will be, and damage may occur if you are not careful. If the clearance is excessive it can be harsh or damaging to other valve train components. Therefore, for prolonged running of the engine it is not recommend to increase the amount of lash by more than +0.004" from the recommended setting. Nor is reducing the lash by more than -0.008" recommended.
 
The common gains that people see will be that by reducing the lash will increase top end (upper RPM power) horsepower, and increasing the lash can improve low end torque and acceleration.
 


Closing Remarks & Tips:

  • As mentioned above, you can change the power band a bit on an engine using a solid lifter camshaft by varying valve lash settings. A looser lash setting increases the low-end power of the engine where a tighter lash increases top-end power. Also, be careful because the valve lash is the "Cooling Time" that the valve needs on each cycle. If you have too little, or no lash, you take a chance of burning the valves.
  • Using roller rocker arms dramatically increases valve guide life, increases horsepower and also maintains better valve lash settings. Use them when you can! Shaft style rockers are best (less deflection). Stainless steel rockers provide less "over the valve weight", which is GOOD. Aluminum, though less expensive will deflect more and increase the actual weight over the valve stem. The added weight may not seem critical to you, but this is considered rotational weight, which slows down all the components related to it.
  • Additionally, too loose a valve lash setting can damage the valve stem and increase possibility of premature failure of the roller rocker tips. If using OEM style, stamped steel rocker arms, you could fracture the arm or gall the fulcrum.
  • Engine materials, engine operating RPM, and valvetrain deflection contribute to varying valve lash settings. The higher the RPM, the cheaper the parts you use, and the performance and reliability differences between types of materials contribute to more frequent valve lash adjustments. (By the way, while you are in there with the valve covers off ... test your valve spring pressures. There are tools available for installed testing of spring pressures).
  • There is FREE horsepower when using a Roller Cam ... if you can afford it, do it. Plus, when using a roller cam, you can change camshafts without the need to change lifters or the go through required break-in procedures, which is mandatory with Hydraulic or Solid "tappet" camshafts.
 
Discuss this topic in our forums here:
 
Back To Top