The Lifter/Cam Relationship - Engine Builder Magazine

The Lifter/Cam Relationship

They are lifters, and they are critical to proper engine operation.

“On the outside they look the same, but the inside is where the big difference is,” says Scott Reynolds of Scorpion Performance. “The mechanical or solid lifter is just what it sounds like: solid with no internal movement. These lifters are designed to be set at lash (clearance) and are to be used on camshafts that are designed for a lash setting. They require periodic adjustment and are normally used for higher rpm.   

“Hydraulic lifters are designed to run with no lash and have a moveable pushrod seat controlled by engine oil, hence the term ‘hydraulic’. They are normally adjusted to a preload (from zero lash) setting and use a camshaft designed for a ‘no lash’ situation. They are basically a ‘set and forget’ lifter because of the preload-type adjustment and are normally used up to 6,500 rpm.”

Flat tappets (what many people might consider the “normal” lifter), both hydraulic and mechanical, have a flat face that rides against the cam. “In reality the face has a slight crown (convex) to help the lifter spin or rotate when the cam lobe moves past it,” says Reynolds.

“One of the big industry changes was in the mid-’80s when the automotive market went to roller lifters,” explains Dave Popp, TopLine/Johnson Hylift. “Diesel engines caught on a little bit later. The roller bearing in a diesel is under such a harsh environment that the needle bearings are often lapped out. There are still diesels produced today that are flat tappet.

Roller lifters have an obvious difference, and can be either hydraulic or mechanical in design.

“Roller lifters utilize a steel needle bearing roller,” explains Hunter Betts of Enginetech. “The roller contacts the camshaft lobe and ‘rolls’ across the lobe face. The roller lifter greatly reduces friction and virtually eliminates cam lobe wear.”

Another design lifter – the bucket lifter – contacts the camshaft lobes and rotates similar to flat faced lifters. “The primary difference here is the bucket lifter transfers motion directly from the cam lobe to the valve stem thus eliminating the need for rockers and pushrods. Bucket lifters greatly reduce reciprocating mass within an engine,” Betts says.

Another huge change has been the transition from cam-in-block overhead valve engines to overhead cam engines. These engines, often with multiple cams in their cylinder heads, do not use conventional lifters but instead use lash adjusters. The lash adjuster is usually found in an overhead cam engine. It stays steady in the head. The foot of the rocker arm will be on the valve and the seat will be on the tip of the lash adjuster. The cam usually rides in the middle. The action of the cam pushes down the rocker arm, which pivots on the tip of the lash adjuster.

“The conventional engine of the Chevy 350 and the Ford 302 is still popular, of course, but has been taken over by engines that use lash adjusters instead of the old lifters,” Popp explains. “Today, for example, in Ford’s modular engines, the 4.6L, 5.4L and Scorpion design engines use a lash adjuster.

“The components and engines are getting smaller,” he continues. “We’re seeing a lot more of the little four-cylinders and V6 engines that use little encapsulated lifters at the end of the rocker arm and a lot less of the single cam, 16-lifter pushrod V engines.

Lash adjusters act like hydraulic lifters to compensate for valve lash as component temperatures change reducing lash and also compensate for valve train wear that increases valve lash,” says Enginetech’s Betts. “The primary difference between a lifter and lash adjuster is that unlike a lifter, the lash adjuster does not contact the camshaft lobe.”

This is a bonus to both manufacturers and engine builders: because it’s not a mechanical wearing surface there aren’t any special castings or carbides to worry about. They’re smaller, yet clearances are still critical, so the accuracy of the manufacturing has to be to a very high level, say the experts.

Whether it is a mechanical, hydraulic, flat tappet or roller style, the lifter is one of the most important components in the engine. The lifter technology determines how the camshaft will react to the rest of the engine combination. And the technology that goes into it is simply amazing.

“It’s all about the tolerances,” says Popp. “We hold the roundness of the OD grinding of the parts down to 20 millionths of an inch and we match the internal components to the ID grinding of the body to 35 millionths of an inch.”

It’s the highest-toleranced part in an engine. It’s very critical and yet people think one size fits all. This technology continues to impact the market and is a good reason why “one size fits all” doesn’t work in this market.

Jay Ryan from SB International agrees that times may be changing but believes some things will stay the same for the foreseeable future.

“Now, the cam-in-block engines – like the Chevy 350, the big block Chevy and the 8.1L GM still use a roller-style lifter and pushrod. Unless they completely do away with cam-in-block engines, which I don’t foresee in the near future, we’ll continue to sell lifters.”

As Popp points out, clearly the rumors of the demise of the conventional lifter has been overblown.

“For 20 years they have been saying the flat tappet was going into extinction. But if you look at the numbers, just in 350 Chevys alone, the volume is staggering. Just think of how many of them are still on the road. If you think that 10 percent of what’s in use will ever get rebuilt and just 10 percent of those every year, it’s still a couple million lifters a year. So the demand never really went away,” Popp says.

“We were OE for Ford on the Flathead back in the 1940s, we’re still producing 40,000 of these lifters a year,”?he says. “I regularly have customers looking for parts that we designed in 1946 and obsoleted in 1967.”

You can call it proliferation or a testament to the ingenuity of the OEM engine manufacturers but the range of product styles is staggering, says Popp.

“Just ourselves, in the standard flat tappet, we actually produce about 90 different varieties,”?he says. “And that’s just the current stuff.”

There have been a tremendous number of design changes thanks to the “influence” of the EPA, according to SBI’s Ryan. “The bottom end of the motor is not where the fuel economy is. They have to constantly rethink the cylinder head. That plays right into he valvetrain being able to maintain the timing, the air and the fuel but, the OEs constantly change the design to lighten it up, to compact it.  And it’s all driven by the EPA’s demand to get more mileage out of a gallon of fuel.”

For many suppliers, there are only so many part numbers they can stock, so while conventional lifters certainly have a place in the aftermarket, Ryan believes future engine designs may lean toward a more unified design.

“You’ll always have some variation, but the styles will become more confined to a smaller number of designs,” says Ryan.

The automakers are learning that you can have a “one-size fits all” if the design is right. But, when it comes to OHC engines you’ll still have different versions.”

If it seems like the lifter is one of the most complex components in the engine, says Ryan, you’re correct. “The sad thing is, there’s not a lot of profit being made. To be such an intricate part of the engine it amazes me that they can be produced for what they are.”

The market has definitely been hit hard from a variety of directions. Loss of leading suppliers led to a massive shortage nearly a decade ago. Lower quality casting materials used in some products gave a black eye to the reputation of many other manufacturers. And engine durability has played a part in making lifters less understood.

“Weight and durability are crucial features of quality lifters, but durability is most important,” says Scorpion’s Reynolds. “Lifters must have the durability to last until the end of a race or the end of a race season. In addition to its own proprietary acicular carbide testing machine, our lifters are also thoroughly tested for durability on Spintrons and dynos.”

Reynolds says the entire valvetrain relationship has to be considered in order to get the best power and durability. “The cam and lifters have to be compatible, the pushrod has to be rigid enough to avoid deflection, the rocker arm has to be the correct ratio and stiff enough to transmit motion to the valve, the spring has to have enough travel and sufficient loads to control the valve train for the rpms, and the valve needs to be strong but still be light for this all to happen correctly.”

Dave Popp says he has seen people try strange things to extend the life of their lifters, whether the efforts are warranted or not.

“We’ve had people take apart the lifters to try to clean them rather than buy a new set (sometimes they just can’t get the replacement parts). Then they’re stuck because they can’t get them back together again. Or if they do, some may be tight and some may be loose and they’ll have ticking noises or bind up,”?Popp says.

“In the mid to late ’90s, the U.S. market was remanufacturing about 3 million engines a year. It is now about 1.3 million,”?says Enginetech’s Betts. “Also, many of our customers reuse the roller lifters and roller cam during rebuilds since they don’t physically wear. A good cleaning and inspection of the cam and lifters is necessary if these parts are going to be reused. Roller cam lobes don’t usually wear but the roller cam journals do. We offer undersized cam bearings for customers that grind and polish damaged roller cam journals to a new and smaller diameter.”

Betts explains that the rebuilder must replace the cam bearings anyway so the only added expense in reclaiming a roller cam with damaged journals is the labor to grind and polish the used cam. Grinding and polishing damaged cam journals can save the rebuilder about $150 by not having to purchase a new roller camshaft.”

The relationship between the cam and lifter – in a flat tappet cam – is critical, explains Popp. “The taper and the crown of the camshaft lobe isn’t flat across. It can be anywhere from flat to a .002? taper across the cam face. That taper has to match the crown of the lifter, otherwise you’ll get an edge-riding condition and a non-rotational spin. The lifter has to spin so you get even wear on the whole face of it.”

If the lifter has the same slope you would have a line contact, and the distribution of the load is spread over an infinitely large area compared to having the wrong contact. In an extreme case, says Popp, such as if the camshaft has a very severe taper to it and the lifter was flat, the lifter will touch at just that little point. This would cause a huge point contact load and it would probably yield either the camshaft or the lifter material – and usually it’s the camshaft that fails first.

“The relationship of all the valvetrain components is important, but if you boil it down to two pieces of the system working together, the cam/lifter relationship is probably one of the most important,” says Scooter Brothers, Comp Cams. “It is critical on flat tappets as far as wear is concerned and they have to work together for performance to be what it’s supposed to. It’s as much a player in the valvetrain as any two parts you can pick.”

Brothers says OE designers have to work in a fairly small box when they design a cam for a particular engine. They have a lot of constraints. It has to work in a lot of environments, with a lot of different drivers – it has to work across the board.

“The good thing about the performance world is our customer doesn’t have to make those compromises because he knows exactly what he wants his engine to do. That allows us to do some things the OE designer couldn’t do, such as open the valve quicker,” Brothers says.

“When you increase the acceleration of the lifter, which is what most performance designs to, then you can maintain reasonably well your seat timing which controls the idle and controls the vacuum and controls some of the low-end torque. Yet you’ve increased your area up high, which helps your airflow and increases your horsepower. So with a street-type application you can pretty much have the best of both worlds by redesigning the lobe and increasing the rate at which the lifter opens,” explains Brothers.

He says the transition from flat tappet to hydraulic roller camshafts has been primarily an effort to allow the valve to open quicker.

Consider that as being the old traditional flat tappet lifters. Now if you want to do a similar thing – and it’s a lot what the OEs have done – you can go to hydraulic rollers, which again allows the valve to be opened quicker.  “You are able, because of the design and the relationship between the roller and the lobe, to accelerate the valve a lot quicker and use a little more lift and work the system a little harder without compromising durability or emissions or anything the OE guys have to typically work with.

“Now, if we want to go up even further to a high performance race-type engine, you can go to a mechanical flat tappet, which, like every other of these steps, just makes the valve open quicker. The same with the relationship from the hydraulic roller to the mechanical roller. It allows the valve to open quicker and keeps a certain amount of bottom end power yet increases your top end,” Brothers explains.

Cam Construction

Flat-tappet camshafts, whether mechanical or hydraulic, are all castings. They’re basically a very simple, yet pretty decent, alloy of cast iron that is flame hardened so they have a very deep hardness.

“The reason the cast iron works so well, is, when you flame harden it, the carbides are pulled out of the cast right to the surface. Those carbides give you a very hard surface for the lifter to wear on,” Brothers says. “However, when you have a flat tappet lifter with those carbides, you need a certain lubricity and additive package to make that work.”

The changes in lubrication technology have impacted the cam and lifter partnership as well as other engine components. Hunter Betts says premature wear of cam lobe and lifter faces with flat tappet lifters and cams is a very real problem. “Improper break-in procedure is one reason,” he says. “The other is an absence of enough ZDDP in the break-in oil.”

Brothers confirms this: “The zinc can be a little detrimental to the catalytic converter, so for 100,000 mile warranties they wanted to get rid of that. Now we have to put it back in if we’re putting in a flat tappet cam.”

As you go up in performance, the roller lifter’s pressure angle (the angle at which the wheel “digs in” or hits the lobe as it’s trying to open) is much greater than it is with a flat tappet so it requires manufacturers to use a different material. In some cases, say manufacturers, austempered steel casting is used on the lower performance hydraulic castings; most of them go up to a billet steel camshaft.

“Some of the NASCAR cams and lifters are made out of tool steel because of wear,” Brothers says. “They found a package they can run without fear of having problems. Most are probably running the cam two or three races and the lifters only one.”

At this level, Brothers says the relationship is CRITICAL, because it’s about a $5,000 package for the cam and lifters.

Enginetech’s Betts sees another area of concern. “Oil contamination is by far the major cause of lifter complaints. The hydraulic lifter is the most sensitive oil filter in an engine. The internal clearance between the plunger OD and body ID is only about .0002?. Any solid contaminants that enter a lifter are likely to muck it up. When lifters are returned to us with a complaint of ‘noisy’ or ‘won’t pump up’ we find solid contaminants inside the lifter about 99.9 percent of the time.”

Reynolds from Scorpion agrees that debris is an issue: “The main problem we see with hydraulic lifters is ‘bleeding down’. Most of the time this is caused by debris getting into the hydraulic unit causing sticking or getting into the check valve causing ‘bleed down’. Some of the types of debris we’ve found include metal from engine machining, material from a wear issue in the engine, gasket material and gasket sealer.”

Reynolds continues: “In roller lifters the prominent issue seems to be bearing failure. This is normally caused by one of two things: in an engine with high spring loads that spends too much time at low rpm (driving on the street), the lifter will overheat causing the bearing to fail. Or, valve bounce at high rpm, will fracture the rollers and cause bearing failure due to the shock load.”

Jay Ryan says that staying up to date with today’s lifter and cam procedures is more important than it was 20 years ago.

“Most of the people I deal with are up to speed but my suggestion would be to keep up with the changes. Just because we used to do it this way doesn’t mean we do it this way now. For example the VW 1.8L engine, the 20-valve engine, there is a specific bleed down procedure for that engine. If it’s not followed, you could have a catastrophic failure. So keeping up with changes like these is important.”

What Don’t Builders Know?

When it comes to performance lifters and cams, understanding what you don’t know can often be the best thing, according to industry experts.

“What most people don’t understand is it’s not just lift and duration,” says Brothers. “Cam lobes are designed in a very specific way to move the valves in a very specific manner. We probably have 13-14,000 designs in our cam library. If a guy calls up and says he needs a cam that’s 260 degrees and .400? lift, we probably have 25 cams that fit that. What they don’t understand is that the very subtle differences are huge in camshafts.”

All the pieces of the system have to match in order to have the best results and camshaft suppliers we spoke with for this article say the best and easiest thing an engine builder can do is build a relationship with a good supplier.  

Experts say we’re asking so much of engines these days that the luxury of experimenting with parts has gone away. 

“The line we walk is razor thin and if we don’t have exactly the right cam with the right lifter and the right pushrod and the rocker arm and valve spring with the right weight valve, the engine’s just not going to operate properly. And if you build a relationship with a good cam company, they’ll be able to help you work through those questions,” says one cam manufacturer.

“No one has to worry about looking like an expert when he calls,”?Brothers says. “In fact, the guy who looks like an expert can often be a problem.”

Jay Ryan concludes that it’s hard to know what you’re getting into WITHOUT that relationship with a supplier.

“There are many engine builders who are very educated,” he says. “They know what they want and know what they’re using when it comes to other components (cam design, valvetrain geometry, etc). Typically, a savvy builder can make the determination but the majority of them will rely on their supplier for assistance.”the cam and lifters have to be compatible, the pushrod has to be rigid enough to avoid deflection, the rocker arm has to be the correct ratio and stiff enough to transmit motion to the valve, the spring has to have enough travel and sufficient loads to control the valve train for the rpms, and the valve needs to be strong but still be light for this all to happen correctly.the relationship between the cam and the lifters 
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