Valve Adjustment Procedure
Hydraulic Lifter/Valve Adjustment
1. Remove the valve covers, and pick a cylinder you are going to set the pre-load on.
Only do one cylinder at a time.
2. Rotate the engine in its normal direction of rotation (clockwise) and watch the exhaust valve on that particular cylinder. When the exhaust valve begins to open, stop and adjust that cylinder's intake rocker arm.
3. To adjust, back off the intake rocker arm adjusting nut and remove any tension from the push rod. Wait a minute or two for that hydraulic lifter to return to a neutral position. The spring inside the lifter will move the push rod seat up against the retaining lock, if you give it time to do so.
4. Twist the intake push rod with your fingers while tightening down the rocker arm. When you feel a slight resistance to the turning of the push rod, you are at "Zero Lash". Turn the adjusting nut down one half to three-quarters of a turn from that point for street applications. Use 1/8 to 1/4 turn for race applications. Lock the adjuster into position. The intake is now adjusted properly.
5. Continue to turn the engine, watching that same intake valve/rocker you just set. It will go to full open and then begin to close. When it is almost closed, stop and adjust the exhaust rocker arm on that particular cylinder. Loosen the exhaust rocker arm and follow the same procedure described before in steps 3 and 4 to adjust this rocker arm.
6. Both valves on this cylinder are now adjusted, and you can move on to your next cylinder and follow the same procedure again.
There may be some initial valvetrain noise when the engine is first fired up but once oil pressure has stabilized and the engine heats up, it should quiet right down to a normal level.
Remember that some racier camshafts will have a mechanical sound to them and will not be a silent as factory units.
Pushrods
The #1 Cause of Valve Train Problems
Crane Cams provided some nuggets of very important info on these often overlooked parts...
Crane has always taken pride in trying to produce only top-quality camshafts and valve-train components. One problem that occurs however, is that we never know exactly how the products are going to be used. When you think of the number of mathematical permutations about all of the combinations of cam profiles, valve springs, cylinder heads, pushrod lengths, intake and exhaust systems; you immediately realize that no manufacturer could ever test for everything. It is even impossible to test for 5% of the total possibilities. So we do the best we can!
Much of our product development time on roller lifters, rocker arms and valve springs is spent on durability testing with different combinations of related components. One inescapable fact has emerged from several years of testing: it is impossible to have a pushrod that is too stiff! Pushrod flex is a major cause of roller lifter failure, early valve spring load loss and excessive valve seat wear.
Consider the pushrod as if it were a pole-vaulters pole. When the lifter first starts to open the valve (especially at higher engine speeds against stiff valve springs and/or high residual cylinder pressure), the pushrod bends and then snaps back. The “snap-back” can send the rocker/valve spring assembly on an uncontrolled journey that causes “valve-train separation” (lash between lifter and pushrod, pushrod and rocker and rocker and valve).
When this separation is finally eliminated by the valve spring, the lifter can slam violently against the cam lobe and the valve can slam violently against its seat. If this action persists, lifter axle and wheel failure can result. Additionally, excessive valve seat wear and valve damage can occur, as well as accelerated valve spring load loss; not to mention camshaft lobe failure!
“Valve-float” that is automatically attributed to the valve spring design is frequently the cause of excessive “springiness” in the pushrod. This is especially true on long pushrod applications.
For instance, lifter failure and valve seat erosion on the exhaust (but not the intake) of a Big Block Chevrolet might be attributed to bad components or the wrong valve spring; however the longer exhaust pushrod just might be the real culprit. Almost every time that we have increased the stiffness of the pushrod, benefits have been observed. This has been true even when the pushrod increased in weight.
This happens because the lever advantage of the spring working through the rocker ratio means that weight on the pushrod side of the rocker fulcrum is not nearly as critical as weight on the valve side.
The only occasion where we saw a power loss was when the pushrods that we were using gave us “symmetrical lofting” of the valve. This “controlled” lofting actually added area under the lift curve. When we replaced the pushrods with stiffer designs, the “controlled loft” (and extra area under the curve) was lost and power decreased.
Be advised, this is a rare occurrence and “controlled, symmetrical lofting” usually only occurs in a relatively narrow RPM range. Without availability of a Spintron, dyno, and other diagnostic equipment, it would be very dangerous to count on “controlled lofting” when engineering a valvetrain!
The point of this presentation is that if you are having valve train issues: reliability, RPM capability, power output, broken parts, etc., look at the stiffness of the pushrod that you are using. By their very design, straight pushrods have their own “critical frequencies” that can aggravate other frequency issues in the valve train.
When possible, we recommend the use of “double-taper” pushrods. The “double-taper” design almost necessitates the use of shaft-mounted rockers, but they really minimize pushrod problems.
Pushrods seem very straightforward and uncomplicated, but don’t let their appearance fool you. They are among the most notorious gremlins that live in our engines and drive us nuts!!!
^^ from the FTI website
