Ford Alphabet Cams: Everything You Need to Know About 303 Cams

If you are building up a Fox Body Mustang, chances are that you’ve heard of the Ford Racing cams (E303, B303, ETC.), commonly referred to as the “alphabet cams”. Each camshaft has it’s own pros and cons, and each will perform best at different things. Before I tell you about the alphabet cams, you should know that these cams were all designed over 20 years ago, and designed for the masses. They are also known for poor quality control and are lacking in power output compared to modern aftermarket cams.

Modern age technology has allowed companies like Anderson Motorsports to develop camshafts strictly using computer programs to figure out what performs and what doesn’t.

With that said, Alphabet cams are still good cams, especially if you’re on a budget. However, they are technologically inferior to modern camshafts.

Ford Racing Cams

E303 Camshaft

The E303 camshaft is the mildest of the ford racing cams as you might be able to tell from the specifications. It’s known for its excellent street ability and decent track performance.


The E303 camshaft provides plenty of torque way down low for great driveability but at the cost of absolute top end power. I personally love this cam for a daily driven Fox Body Mustang. However, the lack of sheer top end power makes it less desirable if you plan on doing any racing.

  • Street

B303 Camshaft

The B303 camshaft is a nice step up from the E303 cam. It retains the excellent street ability but moves the peak power up a couple thousand RPMs. This helps improve top-end power, but it loses a small amount of torque down low. Personally, I think te B303 is the best street cam, especially if you plan on doing any sort of street racing.


The B303 camshaft is often used in various motorsports, because of its mid-high rpm power. If you plan on doing absolutely zero racing whatsoever, this camshaft might not be the best fit. However, most of us have the occasional street race where that extra horsepower up top is necessary.

  • Street/Track

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F303 Camshaft

The F303 camshaft is loosely referred to as the “boost” cam because the F303 cam makes the best power under forced induction when compared to all the other alphabet cams. There’s a whole host of reasons why it makes good power under boost, but that’s not something we’ll dive into in this article.

F303 Cam

Unless you’re planning on boosting your Fox Body don’t even bother with the F303 cam. Although it’ll make way more power than the stock camshaft, it won’t make the same naturally aspirated horsepower as the other alphabet cams.

  • Forced Induction

X303 Camshaft

The X303 camshaft is basically a dedicated track cam. It has less duration than the F303 cam, but it has the most lift out of all the alphabet cams. The X303 camshaft is not very street friendly and makes most of its power way up high in the RPMs.


This cam won’t perform all that well without a set of high flowing aluminum heads.

  • Drag Strip

Z303 Camshaft

The Z303 cam is a lot like the X303 in the sense that it’s really designed for off-road track use. It has the longest duration and highest lift out of every 303 cam at 228 intake/228 exhaust and 0.552 intake/0.552 exhaust. Just like the X303, the Z303 isn’t very street friendly.

As with all big cams, the Z303 really won’t perform as you might expect without a set of aftermarket heads. With the smaller cams such as the E303 stock heads will work okay, but with big cams, you really need to upgrade the heads.

  • Drag Strip

The Down Side

Like I mentioned earlier, these cams are very outdated. They were designed with single plane technology and were built for the masses. Modern technology has allowed speed part companies to develop camshafts that make more power, more torque, and are more drivable.

The alphabet cams are also notorious for their terrible quality control which results in cam lobes that are all slightly different than each other. I had an E303 cam in my Fox Body, but if I were to do it again I would go with a modern camshaft.

The Importance of Cylinder Heads

If you just install an alphabet camshaft and nothing else, expect to be disappointed. The stock cylinder heads on the 5.0L are terrible. Even if you port and polish them, they still suck. To get the most of out an alphabet cam, especially an X303, you need to install a set of aftermarket cylinder heads.

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The common upgrade is GT-40 heads. They are better than the factory Fox Body heads, but they aren’t all that good either. A set of aftermarket aluminum cylinder heads will do wonders for your 5.0L.

My Fox Body has a set of Edelbrock E-Series street heads. Combined with the E303 camshaft it made a ton of horsepower and a ton of torque. Although it was never dynoed, I would guess that it made 300whp.


The E303 is an awesome street cam, making power down low. The B303 is a good motorsports cam, making power in the middle. The F303 is an awesome cam for sub-600hp forced induction engines. The X303 is a great drag strip cam, making lots of power up high.

The reason all of these cams are popular is because they’re dirt cheap, ranging from $100-200, and make decent power especially when paired up with a set of high flowing aluminum cylinder heads.

However, I personally recommend spending the extra money and getting a modern camshaft that has a dual-plane lobe design. Or better yet, a custom made cam to match your driving needs and cylinder head flow.

Author: Bryce Cleveland

Bryce is a die hard car fanatic. When he's not working on his Jeep Cherokee, he's beating it up in the desert. He started Dust Runners Automotive Journal in 2014 and continues to write content for it as much as possible.

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