Ford’s famous Alphabet Cams (a.k.a. Letter Cams) have been around for decades and are often the go-to choice for Mustang owners looking for more performance from their 5.0L engine.
Ford Performance designed these cams for the 1985-and-up 5.0L/302 roller cam engines with 1.6 ratio rockers. On engines running electronic fuel injection (EFI), these camshafts are only compatible with mass air induction systems.
We’re going to look at four different cams from the “alpha” cam family: E303, B303, F303, and X303.
You can think of each cam as a performance tier, starting with mild street performance and ending with track use.
Here’s a quick overview of each cam’s basic qualities, and you can get the full spec breakout in the table below.
Ford Alphabet Cam Characteristics
E303
The E303 adds mild performance improvements across the rpm range.
B303
The B303 takes the performance up a notch without losing much streetability.
F303
This cam makes power up to 6,200 rpm and is a good complement to forced induction (e.g. supercharging). You may have to modify your pistons for proper piston-to-valve clearance. (Recommended for manual transmissions.)
X303
You’ll gain torque and power up to 6,500 rpm. Like the F303 cam note above, you should check valve clearance and modify your pistons accordingly.
Ford Alphabet Cam Specs
| Camshaft | Basic Operating Range (rpm) | Intake Duration at .050" Lift | Exhaust Duration at .050" lift | Intake Duration (Advertised) | Exhaust Duration (Advertised) | Intake Valve Lift | Exhaust Valve Lift | Lobe Separation |
|---|---|---|---|---|---|---|---|---|
| E303 | 2,500-5,500 | 220 | 220 | 282 | 282 | 0.498" | 0.498" | 110° |
| B303 | 3,000-6,000 | 224 | 224 | 284 | 284 | 0.480" | 0.480" | 112° |
| F303 | 3,500-6,500 | 226 | 226 | 288 | 288 | 0.512" | 0.512" | 114° |
| X303 | 2,200-6,200 | 224 | 224 | 286 | 286 | 0.542" | 0.542" | 112° |
For more specs, check out this data sheet from Ford Performance.
Additional Upgrades
These camshafts require new valve springs. Ford Performance says you’ll need springs rated at a minimum pressure of 120 lbs. (closed) and 295 lbs. (open).
For automatic transmission applications, Ford Performance recommends a torque converter with higher stall rating than stock when using these camshafts.
I HAVE A 1991 MUSTANG GT THE QUESTION IS IF I INSTALL A E303 CAM I GOT TO MODIFY MY SOMOTHING IN THE COMPUTER OR NOT?
I have a f303 camshaft in my 1996 Ford explorer 5.0 swapped ranger with automatic and I changed nothing and engine runs fine idle is a little lower but has no issues driving or stalling out
Derrick did you update the valve springs when you changed to the F cam? I see so much bs about any aftermarket cam in an Explorer 5.0 that it dizzies the mind. Heck even for has a disclaimer about not installing the letter cams in the Explorer. Any ECM reprogramming? The 96 would have the GT40 or GT40P heads? Did you do anything performance wise to the engine? I ask because the 95/96 Explorer motor and the 4R70W trans are what I plan on swapping into my 95 3.0 Ranger later this year.
I, also, have a 91 GT. I got a B303, and didn’t change the computer. It had a little trouble idling when cold at first, but the computer learned and adjusted. Now it cold starts and idles with no worries. I think you’ll be fine with E303. These computers were designed to adapt a little bit.
I have been using the B-cam and X-cam since 1994 and absolutely love these lettered cams. I will tell you though that using any of the Motorsport cams combined with TFS Twisted Wedge heads will give you the Best performance then any other camshaft. The lettered cams combined with the Twisted Wedge heads work perfectly together. One other thing, I have used the X-cam & 1.6 rockers on an 87-89 302 without having to notch the pistons. As long as you have the Valve Springs .550 you’ll be just fine….
Will they work with stock heads as well
You know the valve springs part number?
Were these originally numbered 302? I thought I had an X302 cam in my motor, bought in 2003, trying to find out more info on it. I have the spec card.. says .542 lift on the intake and .563 on the exhaust. Duration @ .050 224 intake 232 exhaust. 112 lobe sep. The receipt says “4018”.
Are there any markings on the cams to ID what it is? I bought a used cam, seems to really wake up the engine around the 3200RPM mark. It was supposed to be a stock cam according to the guy I bought it from (I have a speed density ECU).
Was wondering if anyone has used the X 303 cam and if so was the piston to valve clearance ok or did you have to modify something
I’m running stock bottom end and x303,1.6 rockers. I would check the clearance if you can but I have had no issues at all with clearance, I clayed the pistons and had plenty of room, but if possible check.
Hay que modificar el Piston hacerle NochPiston
Sounds like you have a Trick Flow-2
I have a 89 5.0 with a scat 347 stroker! Will I have any clearance issues with the xcam
I ran that combination and had no problems. Of course, clay the piston to valve clearance.
i’ll got a 83 Ford F/100 5.0/302 stock now i want a 500 h.p. I need to know what transmission and stall Converter.
I wanna go the Cams shaft E/303or the X303 in my 83 Ford F/100 this is my toy for 2021 I need to know this as soon as possible bcs I got a point to prove to these Fellow who don’t Ford ain’t got it ok thank you The Graveyard Rider know as jdub.
I honestly have no idea what you are saying right now but X303 (2* retarded)/Flotec heads (heavily modified), stock bottom end, 0 deck block, .56cc milled heads with .027 gaskets, 1.72RR, windage tray, elec water pump, 102 octane, 750 brawler on an air gap with a 2 inch spacer gave me 458hp at the flywheel. Bear in mind this is literally max effort on a stock bottom end but you get the idea. Thing made retarded good power and will live happily there for years.
why not go with the dart heads or 202 valve.and 1.8 valve heads thats old school high performance. but works. change from 3 1/2 inch throw arms to 5 1/2 ince throw arms.
I have an x303 cam in a stock bottom 302 , set of gt40p heads , Anderson spring upgrade , cosmetic.060 compressed head gasket ,1.6 roller rockers , Victor Jr air gap intake , Holley 750 quick fuel carb ..1 fogger system complimented by a second plate system …
I hope this reaches you. I have the same set up in my 92 fox. Do you remember what jets your running in that 750 Holley.
How’s it running?
Dart racing Heads will work best
lol
will the E303 cam work in a 94 F-150 302 engine with mass air?
I have a 1994 mustang gt, with these modds, Holley systemax heads, upper and lower intake with 1 inch spacer,Ford racing x303 cam shalf, 75mm throttle body, 30lb injectors Bosch, and a aftermarket ECU, Am planning to boost the engine with a vortech supercharger with about 10lb boost,…. My question is do I have to change the x303 cam to a b31 cam from Anderson Ford motor sports or it will be ok with x303 cam can someone please advise me which way to go with this.
Hi Guys Butch here from Canada—I am getting a lot of different info about cams–I have an older 1975 non smog 302-and I want to upgrade the cam–I have stock heads and a new bottom end and will change cam bearings be fore installing the new cam .All I am looking for is a little more umph when I press the gas …The engine is pushing a 4700 pound 1948 panel truck and I just want it to rock a little more thanks. I must let you know the engine is carbed** 650 Edelbrock 4 bbl with a matching edelbrock manifold not injected and I was informed whether right or wrong that the 303,s are for injected engines –Is that correct? any help would be appreciated–and what cam is best.
Hey Butch, Click here to contact the Summit Racing tech folks. They’ll ask you some more specifics of your 302 (and your ’48) and will be able to recommend a cam that has that performance mix you’re looking for.
Can someone advise me, weather if the x303 cam will work well with my Vortech supercharger on 10/12lb boost,or should I install a split duration cam like lunati or b31 from AFM