Project LA Thumper: Choosing The Right Cam With The Help Of Lunati

Project LA Thumper: Choosing The Right Cam With The Help Of Lunati

If you are planning to build a high-performance engine, okay, any engine for that matter, parts selection can make or break your end result. There is no arguing that the engine needs a good set of heads in order to flow enough air to sufficiently breathe. However, you also need to have the right camshaft to make the valves move for the right amount of time to deliver and expel the required amount of air.

If you have been following Project LA Thumper, you saw us install the rotating assembly and then how we connected it to the camshaft via a Milodon gear drive. However, I didn’t talk much about the camshaft I chose. The selection of a cam was not made in haste, as I do understand the importance of utilizing a stick with specs that will work in this application. Since I also understand there are guys better suited to help with this selection, I reached out to Will Vance at Lunati to ensure I chose wisely.

Choosing a cam with required (and properly ground) humps is not as simple as opening a catalog, scrolling to the bottom of the page, and selecting the largest lift and duration numbers available. It takes years of experience to fully comprehend all the intricacies of proper cam selection. But while it is possible to have a solid grasp of camshaft fundamentals, choosing your next cam needs to involve more than just guesswork or a scroll through part numbers. It all begins with fully understanding the basics, and most importantly, how those basics apply to you and your engine on a practical level.

Before You Start

The first thing that should be considered, but rarely is, has to be what you are planning to do with your engine. Being honest about what your mill really needs, requires you to not get hung up on horsepower numbers and focus on what exactly you’ll be doing with the car — most of the time. Too often, enthusiasts get focused on high horsepower numbers and low quarter-mile e.t.s. However, unless you plan to race your car a lot, this isn’t the right way to approach the engine build.

“First, you absolutely should have your ducks in a row,” Will quips. “In my opinion, first things first — what are you building [your engine] to be? It doesn’t matter whether it’s a car or truck, two-wheel- or four-wheel-drive… What is the intended usage? Once you know that, we can then build from that perspective. Many times, if the customer will just be upfront with us, whether it is intended to spend more time cruising than racing, or if the build is to just be thrashed around town from time to time, this info helps us get an idea of which path we need to start walking, in the quest for the cam they need.”

Getting a camshaft recommendation from Lunati is as easy as filling out the questionnaire on the website  or simply giving them a call.

Why build an engine oriented toward high RPM if you aren’t going to be spinning it at 6,000 rpm for any extended periods of time? If your engine will actually be spending the majority of its time cruising around town at low RPM (under 4,000) with a perceived occasional trip to the track, keep that solidly in your mind. I did say perceived because all too often, track time never actually occurs. A good rule to remember is, that having the horsepower and torque at the right place in the RPM range is more important than the peak power.

The Perfect Match

Not only do you need to be honest with yourself about how the engine will be used, but you also need to consider the rest of the car’s components. If the engine you build is not compatible with the rest of the drivetrain, you will have a car that does not perform as well as it should. For instance, you should not be surprised if your engine seems sluggish because of a “large” cam being used with a poorly matched converter and rearend gear ratio. Case in point, there’s no reason to have a large, lopey “race cam” if you are planning to run an automatic with a stock stall converter.

Another way to achieve less-than-stellar results is to have a freeway-friendly rear gear ratio that won’t allow a cam with serious duration to ramp quickly into its intended RPM range. This combination will only result in a sluggish launch off idle. Other important considerations include ancillary items. For instance, does your car have vacuum-assisted brakes, what exhaust will you be running, how much does the car weigh, and what kind of driveability and idle quality do you want? To make the selection process easy, we suggest you create a list answering all of those questions before you decide on a stick.

All of these aspects were taken into consideration when selecting a Lunati cam for Project LA Thumper. Don’t tell anyone, but I also spoke to Will before we ordered our cam. That benefit is available to everyone. “By all means, call us direct anytime,” says Will.  “Alex and I are always glad to help a customer pick what will give him or her whatever will be best suited for the application.”

The Lunati Choice We Made

With all of the pertinent information in hand, Will enthusiastically directed me to the Lunati Voodoo line. “For the application, it would be hard to beat the Voodoo lobes. They make killer power, are easy on valvetrain parts, and have some wicked throttle response. Let’s hit it with a duration of 243/251 degrees at .050-inch and open those valves with a .560/.565 lift on a 110 Lobe Separation Angle (LSA). Part number 20200713LK gets cam and lifters or add just the letter K to get cam lifters springs locks retainers and timing set.”

So that’s what I did. I ordered the LK kit since our Trick Flow heads will have suitable springs already installed. The block we’re using is also not a “roller” block and since we wanted to use a hydraulic roller cam, we ordered our lifters in the retrofit design.

Will previously alluded that the cam choice features a 110 LSA, and while most enthusiasts might understand what lift and duration are, the LSA ground into a camshaft can leave many baffled. The term LSA expresses how the intake and exhaust lobes are “phased” with each other. It is measured in degrees of camshaft rotation and is the distance between the centerline point of peak lift on the intake lobe and the peak lift on the exhaust lobe.

Lunati

I told Will I preferred to use a hydraulic roller in this application and he came up with PN: 20200713. It is Lunati’s Retro-Fit Hydraulic Roller. It is a serious street/race cam that needs a minimum of 10.5:1 compression and a 3,200-rpm stall converter. It has a duration of 243/251 at .050-inch lift, .560/.565 inch valve lift, an RPM range of 2,600-6,600, and what Lunati calls a healthy idle quality.

Lift and duration tell what you need to know about an individual lobe, but the LSA tells how those lobes relate to one another and how much overlap is present. Overlap is the brief window of time when both the intake and exhaust valves are open. The LSA typically ranges from 95 degrees on the extremely narrow/tight side to upward of 120 degrees. If we look at the possible LSA spread available, our 110-degree LSA puts us roughly in the middle of the pack.

“The 110 LSA is a happy medium,” Will states. “A wider LSA would help to broaden the powerband but could sacrifice peak power. A lower LSA will make more peak power, but the power curve will become “peaky” as well, meaning it would deliver a narrow power band.”

I am not too proud to admit I sought the help of Lunati to select the camshaft for LA Thumper. Will is a professional and makes recommendations every day. Because of that, I know I have the right cam. Selecting the right camshaft can be a cause of confusion, but if you reach out to the manufacturer with some honest expectations, you can get the camshaft that will best fit your application. Project LA Thumper is sure to be a solid performer on the street and the inclusion of our Lunati-recommended hydraulic roller stick should help deliver some serious power while allowing the engine to be happy while on those Saturday night cruises to the local hangout.

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About the author

Randy Bolig

Randy Bolig has been working on cars and has been involved in the hobby ever since he bought his first car when he was only 14 years old. His passion for performance got him noticed by many locals, and he began helping them modify their vehicles.
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