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Lifter Tech

For years COMP Cams® lifters have set the standard for solid roller lifter technology, but today’s engine’s place an even greater demand on lifters. With today’s aggressive cam designs and increased rpm ranges, look to COMP Cams® Endure-X™ Solid Roller Lifters or the new Elite Race™ Solid Roller Lifters.

Flat Tappet vs. Roller Tappet Lifters

Hydraulic vs. Mechanical (Solid) Lifters

Setting Valve Lash With A Solid Lifter Camshaft

Setting Hydraulic Lifter Pre-load (Adjustable Valve Train)

Setting Hydraulic Lifter Pre-load (Non-Adjustable Valve Train)

 

 


















Flat Tappet vs. Roller Tappet Lifters

In nearly all circumstances, a good roller camshaft design will outperform its flat tappet counterpart. Among the benefits of roller cams are higher tappet velocity, more lift and more area, along with reduced valve train friction (often a 15+ hp increase) and higher engine rpm with little effect on low speed drivability and power.

Roller tappets are also reusable, which makes it possible to swap just the camshaft without the expense of new lifters. And finally, roller tappets are far less prone to wear, allowing higher spring loads, and they are more consistent with today’s oils.

The biggest advantage with a flat tappet cam and lifters is the upfront cost. It can be significantly less expensive to use a flat tappet setup but should you decide to install a new camshaft, flat tappets are not reusable. You will need new lifters as well.

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Hydraulic vs. Mechanical (Solid) Lifters

Both lifter types look the same from the outside, with both having pushrod seats held in by a retaining clip. In a hydraulic lifter the seat moves by means of a hydraulic valve and oil pressure within the lifter. The mechanical lifter does not have a valve and is solid.

The pushrod seat in a solid lifter sits upon an internal step inside the lifter body, preventing it from moving. The hydraulic lifter, on the other hand, has a pushrod seat that sits on top of a moveable hydraulic mechanism which acts like a tiny hydraulic pump. Below this mechanism are a valve and a spring to produce an upward force, moving the seat up against the pushrod when the lifter is on the base circle.

Solid cam designs require a running clearance or “valve lash”. Hydraulic cams are the exact opposite. In a standard hydraulic lifter the pushrod takes up all of the clearance and submerges into the lifter’s pushrod seat approximately .020"-.070". The distance that the pushrod submerges is known as the “pre-load”.

Hydraulic Lifters
Pros
Cons
1. Minimum amount of maintenance is required once the proper preload is set 1. Less stiff at higher engine speeds due to hydraulic valve pumping up with high pushrod forces - forcing oil to squeeze out, reducing the running duration
2. Fully adjustable for any changes in block & cylinder head size
3. Less valve train noise 2. Effective rpm range is limited
Solid Lifters
Pros
Cons
1. More accurate & consistent valve timing throughout the entire rpm range 1. Takes longer to properly set up & requires regular maintenance
2. Not adversely affected by higher spring loads or increased engine speeds 2. Noisier valve train


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Setting Valve Lash With A Solid Lifter Camshaft

First, check the spec card that came with your cam for the correct valve lash specifications. All COMP Cams® valve lash settings are “hot” settings (set at normal engine operating temperature) but will work for initial start-up as well.

Turn the crankshaft in the direction of normal engine rotation until the exhaust pushrod of the cylinder you are adjusting begins to move upward, opening the valve. Adjust the INTAKE lash by tightening the intake rocker nut with the correct thickness feeler gauge inserted between the valve stem and the rocker tip. Tighten the rocker nut until there is a slight drag when moving the feeler gauge. Next, rotate the engine until the intake pushrod fully opens the valve and then goes half-way back down. Adjust the EXHAUST rocker nut (with correct feeler gauge) using the same procedure. Repeat for all cylinders.

After setting your valve lash with the engine cold, start it and follow the appropriate break-in procedures. Due to thermal expansion, your valve lash will now be tighter than it was when the engine was cold. Repeat the adjustment process to ensure that your valve lash matches that specified by your cam card at normal operating temperature.

Note: Check with COMP Cams® on valve lash settings if using aluminum heads or blocks.

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Setting Hydraulic Lifter Pre-load (Adjustable Valve Train)

When installing a hydraulic cam, lifters or rocker arms, establishing the correct lifter pre-load improves both performance and engine life. Insufficient pre-load will create excessive valve train noise and wear. Excessive pre-load will cause rough idling and low manifold vacuum, and can even lead to severe engine damage. With an adjustable valve train, proceed as follows:

Install the pushrods and rocker arms. Be sure the pushrods are seated correctly in the lifter and rocker arm. Turn the engine over in the direction of rotation until the EXHAUST pushrod just begins to move upward, opening the valve. Now adjust the INTAKE rocker of that cylinder. Carefully tighten the nut on the intake rocker while spinning the pushrod with your fingertips. You will feel a slight resistance in the pushrod when you have taken up all of the clearance. This is “zero lash.” Turn the adjusting nut to the specified pre-load – typically 1/4-3/4 of a turn, but this will vary based on the lifter number.

Turn the engine in its rotation direction until the intake pushrod comes all the way up and almost all the way back down. Now set the EXHAUST rocker to “zero lash” and add the specified pre-load. Repeat this process for all remaining cylinders.

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Setting Hydraulic Lifter Pre-load (Non-Adjustable Valve Train)

COMP Cams® recommends using an adjustable pushrod to check the pre-load. Typically, only one cylinder needs to be checked in this process. After applying lube, install the adjustable pushrods and assemble the valve train. Using the same procedure mentioned earlier, adjust the intake and exhaust valves to zero lash by changing the length of the adjustable pushrod for precise fitment. Order a pushrod that is .020"-.070" longer than the pushrod length at zero lash to ensure the proper pre-load.

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