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Valve Adjustment Procedure

Valve Adjustment Procedure

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

Customers often ask what the correct procedure is for adjusting the valve lash on their engines. It seems that anyone they ask provides a different procedure. The information and step-by-step procedure provided below should make it easy for just about everyone reading this article to understand---from the experienced mechanic or racer to the do-it-yourselfer attempting it for the very first time.
Please 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. However, the FIRST step is to forget all the old information we have collected from other individuals, books, and what shop manuals have taught us in the past.
 
Interpreting the information below incorrectly, or trying to merge the steps I present to you below with old knowledge could create more trouble and confusion for you. Next, consider  those things that can affect your valve lash, because you will need some basic common sense understanding of terms and function before we get into this.
 
Before you begin to adjust your valves,  other considerations must be addressed. Simply putting a wrench on something and attempting to follow the cam card, shop manual, or the advice of some friend or relative is not enough. The basics of how the valetrain works is where we begin, after answering a few important questions.
 
What type of cam are you running? (Hydraulic, Solid, Hydraulic Roller, Solid Roller, Mushroom Tappet)
  • Are we using aluminum heads?
  • Do we have the correct valvetrain components in use?
  • Are ALL of our valvetrain parts in proper working condition?
  • Are our valve springs the correct size and tension for the camshaft and operating RPM?
  • What type of driving (or racing) are we going to be using the engine for?
  • Do we have the proper tools and basic knowledge required to adjust our own valves?
The last one above is quite important. If after reading through this and you 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 we describe here to make sure you understand the procedure. If you are wondering what can go wrong, here is a short describing what 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 or reduced 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 us! 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.

 
IMPORTANT WARNING:
 
For those of us with Ford, GM LS-Series, and other engines that utilize "Non-Adjustable" valvetrain ... WE MUST verify that our machinist did their job correctly when setting the valve stem heights, and then WE MUST also verify proper plunger depth when using Hydraulic Lifters. If we switch to solid lifters it is mandatory that we 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 we want to have accurate control of our valve lash setting). Not doing so is asking for serious problems!
 

PLEASE NOTE:

I have written this article somewhat backwards, and I have a very good reason for doing so. I want to expose you to the procedure and then describe how it works and why it works. Experience with our customers has taught me that while I have asked you, the reader of this article, to forget what you may have been taught, such grand requests on my part rarely occur. For some, the whole experience of adjusting an engine's valvetrain is confusing enough.

Instead, I will expose the reader to the procedure to generate thought about how this works.

Please read through ENTIRE article before you begin to adjust your valves!

ENGINE OFF Valve Adjustment Procedure - The Quick and Accurate Way:

First, view this simple chart below for Small and Big Block Chevy Engines. Do you understand what it describes? A more detailed explanation follows 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

 


Explanation:

Camshaft Lobe Terminology
 
First, 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.
Lash - The clearance (cooling time) between the tip of the valve stem and the rocker arm.
Zero Lash - No clearance, rocker is snug to the lifter. On a hydrualic lifer, the plunger is in the uppermost neutral position (not compressed)
 
In the chart above we see that adjustments are 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 heell) 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 cylinders in sequence 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
 
 
For other engines, here are some common firing orders and their opposites. PLEASE VERIFY your engine's firing order. Do not rely on the below list.
 
ENGINE FIRING ORDER OPPOSITES
AMC (most) V8 1-8-4-3-6-5-7-2 (same as example above)  
Buick V8 (most) 1-8-4-3-6-5-7-2 (same as example above)  
Chrysler Big Block & Hemi V8 1-8-4-3-6-5-7-2 (same as example above)  
Chrysler Small Block V8 1-8-4-3-6-5-7-2 (same as example above)  
Oldsmobile (1967-later) V8 1-8-4-3-6-5-7-2 (same as example above)  
Pontiac (1955-1981) V8 1-8-4-3-6-5-7-2 (same as example above)  
     
Ford 5.0L HO, 351W, 351C, 351M, 400 V8 1-3-7-2-6-5-4-8 1 & 6; 3 & 5; 7 & 4; 2 & 8
Ford (most other) V8 1-5-4-2-6-3-7-8 1 & 6; 5 & 3; 4 & 7; 2 & 8
 

Importance of Lifter Position


Lifter Position on Camshaft LobeIf the position of the lifter on the camshaft lobe is anywhere other than on the heel (note image above) where there is NO ramp contact when making adjustments, the lash setting will be incorrect. 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.

In the past we were often instructed by the auto shop teacher or service manual to position each cylinder at TDC (piston at Top Dead Center), and then adjust both valves for that cylinder. However, we often find that this is not the correct procedure to obtain the proper lash setting, especially on modern engines or agressive camshaft profiles. The image at right shows the required position of the cam lobe relationship to the lifter that ensures correct valve lash adjustment.

Roller Camshaft

 
Ensuring that the lifter is positioned on the heel of the cam lobe will guarantee that the valve you are adjusting is fully closed. Any other position and adjustments will NOT be accurate.
 

What about the actual adjustment procedure?

Hydraulic Camshafts:
 
It is time to describe the actual wrench turning. How many of us read or were taught that with a hydraulic lifter camshaft, we must adjust it down to where there is slight pushrod resistance (zero lash) and then turn it down 3/4 or a full turn? I was originally taught the wrong way too, both by instructors and by following inaccurate procedures in various shop manuals. When we followed these methods, our adjustment likely opened the valves slightly, preventing the valves from closing all the way! Our valves were not set correctly!
 
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 we must adjust the valves to fall between 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 removes heat from the valve stem.
 
If the adjustment is too loose, the valvetrain will be loud, and 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 we achieve 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 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. I prefer a "clean" adjustment, and only use the messy way as a last resort.
 
For the messy method I fabricate custom cut-up used valve covers, oil deflectors, and other techniques in an attempt to keep the oil in the engine. Preventing oil from splashing all over the engine compartment and off the ground can be an intense chore that takes consideration and planning!
 
 

Engine "OFF" Hydraulic Lifter Adjustment Tips:

If the engine is complete and installed in the vehicle, warm up the engine by running it until it gets to operating temperature (15-minutes or so). "Cold" adjustments should only be used on new engines on as a preliminary adjustment on the engine stand. Once a new engine has been started and intial break-in procedures complete, readjusting the valves "hot" is recommended.
  1. Have all necessary tools ready and then quickly remove the valve cover(s) while the engine is at operating temperature.
  2. Begin the adjustment procedure by using the chart above, or one to match your firing order and opposites.
  3. 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) --- and adjust the intake valve on "opposite in firing order" cylinder.  Always remember, the opposite valve engine firing order dependent. Know your engine's firing order!
  4. Go to ths opposite cylinder. This technical article uses the common firing order for small and big block Chevy engines as the example, so this would be the #6 cylinder.
  5. Loosen the rocker nut (if using roller rockers there is typically a Jam Nut that you must first loosen with an Allen wrench) on the #6 intake valve.
  6. Take two fingers and spin the pushrod back and forth between them to feel for resistance.
  7. Carefully snug the adjustment nut and STOP when you feel resistance in the pushrod as it applies pressure to the socket in the rocker arm and lifter, this is considered "zero lash."
  8. Turn the wrench 1/8 to 1/4 turn (see below) for performance, racing, or high RPM applications. Turn the wrench 1/4 to 1/2 turn for stock or mild street applications. For applications that regularly operate at consistent high RPM, use the slightly lighter setting of (1/8 turn).
  9. If your valvetrain uses poly-locks, remember to reset (snug) the Allen screw
  10. The adjustment for this valve is now complete!
     
  11. Turn the engine by hand SLOWLY to the next cylinder / valve in the firing order.
  12. Repeat the above steps, starting at #3 through #10, but use the next cylinder in the sequence. In our Chevy V8 example this is the intake valve for the #8 cylinder
  13. Continue through all the intake valves and then start the procedure over for the exhaust.
 

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. 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!!!!
 
Perform this procedure the same way for all the intake valves, then adjust the exhaust valves the same way.
 
PRECAUTION: When working on older high mileage engines or those that use poor quality lifters you may experience a condition where the lifters bleed off pressure (drain the oil out of the lifter body), causing inaccurate valve adjustment. Oil must remain in the hydraulic lifter in order to achieve an accurate valve lash setting. If repeated attempts to adjust the valves using the "cold adjustment" procedure fails, lifters bleeding off may be the cause. two options exist to solve this issue. ONE: replace the lifters or TWO: adjust the valves using the "HOT" running method described below.
 
TIP: One way to tell if this is occurring (bleeding off or no oil) is by watching the rocker arm while applying the 1/8 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 oily 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 AND oil deflectors
  • 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 my distaste for 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 just until the louder "clatter" stops
  • Turn the wrench an additional 1/8 - 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 helps 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:

The steps for solid lifter adjustment are similar to hydraulic lifter adjustments. However, instead of turning a wrench 1/8 to 1/2 turn we will be using a feeler gauge to verify the lash setting.
 
First, warm the engine to operating temperature (about 15-minutes) and then quickly remove both of the valve covers. Follow the adjustment 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 for both the exhaust and intake valves. For some camshafts these clearances will be the same (intake and exhaust), and others may show a value higher (more lash) for the hotter exhaust valve.
 
For example, a cam card recommends a valve lash setting of .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. It is beneficial to use "positive-lock" style rocker arm retention fasteners instead of the basic 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 carefully 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, the 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 can we do in this situation? There is a standard correction factor that can be used to get us close to the required settings. We must now consider the material alloys of the various engine parts, because the thermal expansion of these components affect the valve lash in different ways. Therefore the correction factor used for our 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 in the cam manufacturer's catalog or from the cam card that came with the 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"
WARNING: This correction adjustment is only an approximation, and is only meant to get the valve lash "close" for the initial new engine start up. After properly warming up the engine to normal operating temperatures, go back and readjust all the valves to the specified "hot" valve lash settings.
 

Using Valve Lash to "Tune" Engine Performance

This is a little extra tip often unknown to many engine builders and tuners. Most people do not realize that you can make subtle performance improvements by slightly reducing or increasing the recommended lash settings. NOTE: This is for SOLID LIFTER camshafts ONLY (tappet or roller)!
 
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, by reducing the amount of (hot) valve lash, the valve will open slightly sooner, provide slightly more lift (valve opening), and will close slightly later. This makes the camshaft look bigger to the engine, due to this slight increase of duration and lift. Increasing the amount of (hot) lash the opposite occurs. The valve will open later, provide slightly lift less, and close slightly sooner. Now the 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.
 
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 as well. Therefore, prolonged running of the engine 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.
 
Common gains or performance differences include:
  • Reducing the lash will increase top end (upper RPM power) horsepower
  • Increasing the lash can improve low end torque and acceleration.
 

Closing Remarks & Tips:

  • As mentioned above, the power band can change slightly 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. Careful consideration is necessary for these tweaks 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 whenver 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 reciprocal 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 rocker 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, make the effort to 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 lifter break-in procedures, which is mandatory with Hydraulic or Solid "tappet" camshafts.
 

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