Tech Corner: Selecting the Proper Camshaft for a Beloved Hot Rod

Selecting the proper camshaft is one of the most important parts of building an engine. It essentially controls how the engine wants to breathe and dictates how and when the power is produced along the power curve. When an engine has only one purpose in mind, it eliminates a lot of gray area. For instance, a race engine will live high in RPMs and have a constant demand for as much fuel as possible. But what about a car that you drive around town during the week, and only hits the track on the weekend?

Here we’ll examine the steps you should take when picking the right cam for your street rod.

First things first, you must be honest with yourself and what the purpose of your car is. Are you looking for a lopey idle or a cam to get the best performance out of your combination? You usually can’t have both of those things, so pick one and you’ll compromise on the other.

When we say “be honest with yourself,” we mean look at your combination as what you have, not what you dream it to be. So, if you run a 2200 stall converter and 3.55 gears, don’t pick a cam designed for 3500 stall and 4.56 gears. Likewise, if it’s a daily driver and you run a dual plane intake, don’t pick a cam that is designed for 3500-8000 RPM.

Choosing a cam that doesn’t optimize the parts you have is the biggest mistake we see and can be very depressing for an enthusiast.

Go Big or Go Home… Or Should You?

When building up a muscle car it’s always tempting to up the ante. You’ve got a big V8 in a big car, so naturally you’ll want to make as much power as possible. This is the American way, right? And really, that’s the spirit of these types of vehicles.

The camshaft’s job is to open the valves so air and fuel can flow in and out of the cylinders. While shopping for cams, we all have the urge to look at the stock camshaft’s specs, then look into cams that are dramatically higher in every numerical value. Because if a little is good, a lot is better–right? No.

A large camshaft with big lift and higher duration will make more power, but that doesn’t make them inherently better for every situation. In fact, a combination like that will be really lousy on the street where your car spends most of it’s time below 3,000 RPM cruising around town.

When selecting the proper camshaft, you need a decent understanding of what cam specs mean and how they impact engine performance.
  • Lift. Valve lift tells us how far open the cam lobes will push the valves. This directly relates to how much a cam will flow and how much power it can theoretically make. This must be balanced with how well the heads can actually flow.
  • Duration. This is the measurement of how long the valve is actually open. More duration makes more top-end power at the expense of low-end torque.
  • Lobe Separation Angle. This measurement references the number of degrees that separates the highest points of intake and exhaust lobes on a single cylinder. This narrows and broadens the power band, as well as moves it closer and further from idle. Tighter LSAs make more low-end power and produce the lopey sound everyone loves, but they do impact idle vacuum; wider LSAs, on the other hand, are the polar opposite.

What Does It All Mean?

There’s a lot more to know about camshafts to really dial in your selection. Thankfully, we have manufacturers like COMP Cams to help the layman. The folks over there have been building camshafts since 1976 and know exactly how to match a vehicle to a camshaft.

Now, you will need a few more basic details to aid the selection process. Of course, COMP Cams helps make that easy, too. Each pre-ground camshaft in the company’s catalog tells you what compression ratio, rear gear ratio, transmission type, torque converter stall, induction type, and vehicle weight combination is right for that exact piece. All you need to do is match it up, and you’re good to go.

When it’s time to change the music, turn to the absolute leader in valve train technology.

On top of that, COMP Cams pre-ground cams all exist in a series. The series offer even more insight about the type of engine the cam is meant for and its intended purpose, giving you a better idea as to how it’ll make your vehicle behave.

Below are three of the most popular series within COMP Cams lineup for naturally-aspirated, classic V8-powered cars:
  • Mutha’ Thumper. Designed to appeal directly to a hotrodder’s senses, these camshafts are ground to boost both horsepower and torque over stock for street/strip performance. The name refers to the lopey idle these camshafts are famous for.
  • Xtreme Energy. Designed to bring up horsepower and torque without making an engine uncomfortable on the street, these cams deliver excellent power while retaining high vacuum idle and low valvetrain noise.
  • Nostalgia Plus. There were a ton of famous pre-ground camshaft options in the glory days of these classic cars, but technology has come a long way since then. The Nostalgia Plus line brings those beloved grinds into the 21st century with improved grinds that don’t stray too far from the proven formula, further boosting performance.

Of course, pre-ground cams are only going to get you so far. Make no mistake, they will run great in any engine but aren’t ever going to be a perfect match. The truth is that the exact combination of parts and driving style of your car is going to benefit the most from a custom ground camshaft.

COMP Cams can help you there, too. The company has experts ready to help you sort out the details and come up with a custom grind that’s right for you. Just know that you will need to know every last detail about your car and engine combination to go through the process.

What About Lifter Types?

We’ve been taking it for granted that most street-driven hotrods will go with a hydraulic lifter. For the most part, that is the best type for this application. Still, the type of lifters used plays a major role in determining what a camshaft is good for. That’s why we’re going to give a brief rundown before closing out the conversation.

  • Mechanical. Solid mechanical lifters are favorable for vintage high-performance engines. They’re maintenance-intensive and noisy but are extremely reliable and retain integrity at higher RPMs, allowing for better performance.
  • Hydraulic. Hydraulic lifters are far better for street use than the alternative. They require virtually no maintenance, run smoothly and quietly, and, with modern technology, can support impressively high RPM operation.
  • Roller. Roller lifters have several advantages over flat tappet cams, including reduced friction and more aggressive lobe ramps, allowing them to run more smoothly and easily support higher power. They are more expensive, however, and often require modifications to classic engines to work.

Stay Reasonable

Cam theory goes deep, and the first step into it will leave everyone’s head spinning — even if we’ve merely scratched the surface here. The key takeaway from this discussion should be to stay conservative in your selection.

We’re building hotrods here, and less is more. Going with the biggest, meanest cam you can get will land you an engine that produces far less power than the cam is meant to support in a range that’s totally unusable for the street.

A secondary point should be to lean on the pros. If you’re not sure what is the best match for your engine, just pick up the phone and call COMP Cams. They have the experience, knowledge, and catalog to help you nail down the ideal camshaft for your hot rod.

COMP Cams is the world’s top manufacturer of performance camshafts, lifters, valve springs,
rocker arms and related valve train parts for all race and street performance applications. To learn more about the company’s impressive product lineup, head to https://www.compcams.com.

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