A common issue that can arise when installing a high-performance camshaft is lifter noise. Lifter noise, also known as valvetrain noise or tappet noise, is a common problem that can occur when the hydraulic lifters in the engine’s valvetrain are not properly adjusted or functioning correctly. Lifter noise can manifest as a tapping or clicking sound coming from the engine, particularly at idle or low speeds. This noise can be annoying and can also indicate underlying issues with the engine’s valvetrain components.
Is this Valvetrain Noise I’m Hearing?
First, how do you confirm what you are hearing is in fact valvetrain noise? Valvetrain sounds are what engineers call “1/2 order events”. This means that you get one click or tap for every two rotations of the crankshaft. This is slow enough to count at idle. To do this, make a note of the engine speed at idle via a tachometer. Suppose your idle speed is 750rpm. Divide 750 by 60 to calculate crank rotations per second. In this case, we’ll get 12.5 revs per second. Now, take a stopwatch and count how many seconds it takes for 20 clicks to occur. If you get something close to 6-6.5 clicks per second, chances are you’re hearing a valvetrain noise.
Lifter Preload
One of the primary causes of lifter noise is improper preload adjustment. Hydraulic lifters require a specific amount of preload, or initial compression, to operate properly. If the preload is not set correctly, the lifters may not be able to maintain proper contact with the camshaft lobes, leading to noisy operation. To properly adjust lifter preload, it is important to follow the manufacturer’s specifications and use the correct tools for the job. Improperly adjusted preload can not only lead to lifter noise but also cause premature wear on the valvetrain components. Typical lifter preload is 0.030″ at the lifter, but recommendations vary.
Check those Balls!
Another potential cause of lifter noise is check ball faults. Check balls are small, spring-loaded valves inside the hydraulic lifters that help regulate oil flow and maintain proper lifter operation. If the check balls become stuck or damaged, they can hinder the lifter’s ability to maintain proper oil pressure and cause noise. In severe cases, check ball faults can lead to lifter collapse and complete failure. Checking the condition of the check balls and replacing any faulty components can help prevent lifter noise and ensure proper lifter operation.
Get Down with the Leakdown!
Leakdown plunger clearance is another factor that can contribute to lifter noise. The leakdown plunger is a critical component of the hydraulic lifter that helps regulate oil flow and maintain proper pressure. If the clearance between the leakdown plunger and the lifter body is too large, oil may leak out of the lifter too quickly, leading to noisy operation. If the leakdown clearance is too small, the lifter may stay pumped up too long or hold the valve off the seat unintentionally. This is especially hard on exhaust valves, and can cause them to overheat. Inspecting the leakdown plunger clearance and replacing any worn or damaged components can help eliminate lifter noise and restore proper lifter function, but this requires precision metrology tools. Proper leakdown clearance is on the order of 0.0005″ (five ten-thousandths of an inch) and the tolerance of this clearance is only a few tenths in either direction. To produce such precision components, hydraulic lifter manufacturers must centerless grind the plungers and ID grind the bodies. This equipment is neither inexpensive of trivial to operate, so choose your supplier carefully. The plungers and bodies then have to be select-fitted to a small clearance tolerance range. This requires discipline to do correctly, so again, choose your supplier carefully. If you suspect an issue, ask your supplier to recertify the lifter leakdown performance for you. If they cannot do this, find another supplier.
Viscosity: How Thick is Too Thick?
Lastly, the viscosity of the engine oil used can also impact lifter noise. The viscosity of the oil refers to its thickness and flow properties, which can affect the lifter’s ability to maintain proper oil pressure. Using a properly formulated engine oil that meets the manufacturer’s specifications can help ensure proper lubrication and reduce lifter noise. If you leakdown clearance is too high, a more viscous oil may help you. On the other hand, it may hurt if the clearance is just right. It is important to regularly change the engine oil to maintain proper oil viscosity and this may prevent lifter noise.
Conclusion
In conclusion, lifter noise can be a common issue that arises when installing a high-performance camshaft. Proper attention to lifter preload, check ball performance, leakdown clearance and oil viscosity can help you keep your engine running quiet. That’s something everyone can appreciate, because who wants to distract from that great rumbly cam anyway?
Epilogue – Should I Soak my Hydraulic Lifters?
There are lots of people out there who love to soak their hydraulic lifters. From lubricating the needle bearings to “pumping them up”, everyone who does it seems to have a reason. If you are going to soak your lifters, likely the best reason is “it can’t hurt” (anything other than your wallet, slightly).
Shown above is a section view of a hydraulic flat tappet lifter, but the inside of a hydraulic roller lifter is the same. To “pump up” a lifter, oil has to go from the reservoir inside the plunger (7), past the check ball (4), and into the “high pressure chamber” which is also occupied by the check ball spring (8), check ball retainer (5), and the plunger return spring (9).
Simply soaking a lifter won’t displace air that is within the high pressure chamber. To do this, one can follow either of the following procedures:
Fill and Pump Method:
- Confirm that the lifter feels spongy by depressing pushrod seat (2) with a pushrod or other tool.
- Through the hole in the side of the body, fill the lifter with oil until it comes out of the hole in the center of the pushrod seat (2). This indicates that the reservoir is full
- Using a pushrod or other tool, pump the lifter to draw oil from the reservoir, through the check valve (4), and into the high pressure chamber. Once this is done, the lifter will feel hard. Repeat step 2 and store the lifters with the pushrod seat (2) up until you are ready to install
- Repeat from step 1 if necessary
Vacuum Soak Method
- Confirm that the lifter feels spongy by depressing pushrod seat (2) with a pushrod or other tool.
- In a vacuum chamber, place lifters in a container and submerge in oil.
- Pull a vacuum in the chamber of between 25-30 inHg. Hold vacuum for minimum 10 minutes
- Release pressure
- Repeat step 3. Once this is done, the lifter will feel hard. Store the lifters with the pushrod seat (2) up until you are ready to install
- If lifter is still spongy, return to supplier for further investigation
Using one of the above processes, you can avoid the annoying experience of waiting for your lifters to pump up in your freshly rebuilt engine. Of course, allowing them to pump up on their own in the engine at a speed 2500rpm or below won’t hurt a thing, either.
