How does the new Summit Racing “E303 Plus” cam compared to the original E303? (Image/Richard Holdener)

How much is a cam swap worth on a 5.0L Mustang?

Obviously, the next question should be: What cam swap are we talking about?

The Ford Performance “Alphabet Cams”

When it comes to 5.0L Ford performance, the little 302 has a solid reputation of responding very well to performance upgrades, including cam swaps. One need only take a look at the size of the performance industry that caters to the impressive little small block Ford. Performance parts abound for the H.O., including all manner of forced induction, intakes, heads, and of course, endless cam profiles. Some of the most popular cams, at least in terms of sales, have come directly from Ford, or rather their after market performance division, Ford Performance.

It would be nice to know how many Alphabet-series 5.0L cams Ford Racing (now Ford Performance Parts) sold and continues to sell for the 5.0L Ford enthusiasts. Back in the day (and even now) the E303, B303, and F303 were some of their top sellers, and for good reason. They offered impressive power gains over the stock (mild) H.O. cam, and were proven performers.

Fast forward a few decades, and now Summit Racing has decided to offer a new line of Alphabet-inspired 303 Plus Cams. The only question is, how well do they perform compared to the OG Ford units?

Summit Racing E303 Plus Cam Specs

To find out how well the new Summit Racing cams performed compared to the original Ford Performance E303, B303, and F303 cams, we set up a test. This session would start with the Ford E303 cam compared to the new Summit Racing E303 Plus (PN SUM-8900).

Before getting to the test motor and dyno results, we should take a look at the cam specs offered by each cam. It is also important to note that we compared both cams to the stock 5.0L H.O. cam, since that would be the starting point for the majority of 5.0L owners. The cams offered by Ford for the stock 5.0L actually differed based on the application (auto and stick) and were even adjusted for different years, though not dramatically.

A typical single-pattern, production 5.0L H.O. cam offered .444 lift and 266 degrees of duration. This compares to the specs offered by the Ford Performance E303 cam (also single pattern) of .498 lift, 220 degrees of duration and 110 degrees LSA.

By contrast, the dual-pattern E303 Plus from Summit Racing offers the same 220 degrees of intake duration, but stepped up exhaust duration to 231 degrees (an increase of 11 degrees over the E303). The lift valves also increased from the .498 offered by the E303 cam, to a dual-pattern, .550/.540 lift split. Summit Racing chose to alter the lobe separation angle as well, from 110 degrees to 113 degrees.

Now that we have taken a look at the change to the specs, let’s jump into the test motor and dyno results.

E303 Camshaft Comparison: Dyno Baseline

This test could have been run on an otherwise stock 5.0L motor, but that would certainly minimize the power gains offered by either of the cams (E303 and E303+). Both the stock E7TE iron heads and factory H.O. upper and lower intake would restrict what the cams had to offer in terms of power production. Rather than use a stock motor, I chose to augment the rebuilt 302 short block with a set of aftermarket aluminum heads and decent intake.

I might well test these cams again with an EFI combination (the cams have already been tested and work well on both), but for now, the 302 received a dual-plane, carbureted induction system consisting of an Edelbrock Performer RPM (non Air Gap) and Holley 750 carb. The induction system fed a set of as-cast, 190cc aluminum cylinder heads from BluePrint Engines. The aluminum heads featured a 2.02/1.6 valve package, 60cc chambers (9.4:1) and flowed 250 cfm. The motor was also equipped with a set of 1.75 inch long tube headers feeding 3.5 inch collector extensions.

After dialing in the external jetting on the 750 Holley (via Percy’s Adjust-a-Jet) and timing on the locked-out MSD distributor, the stock cammed 302 produced peak numbers of 368 hp and 364 lb.-ft. of torque. The stock cam offered a nice flat torque curve and decent peak numbers, but we knew the E cams had much more to offer.

Cam Comparison: Ford E303 Dyno Results

The first cam swap involved installation of the Ford Performance E303 cam. Off came the stock valve covers, Crane roller rockers and pushrods, followed by the intake and front cover. This allowed access to perform the cam swap. Out came the stock cam and in went the E303 cam.

Equipped with the E303 cam, the peak numbers jumped up to and even 400 hp (technically 399.9 hp) and 376 lb.-ft. of torque. As we have come to expect from past testing, the E cam offered solid gains through most of the power curve, from as low as 2,500 rpm on up.

Cam Comparison: Summit Racing E303+ Dyno Results

With the Ford E303 cam out of the way, we tore apart the test motor once more time to swap in the new Summit Racing E303 Plus cam (SUM-8900).

Equipped with the new Summit Racing E303 Plus cam, the peak horsepower climbed to 412 hp, a gain of 12 hp over the Ford E303 cam. The peak torque dropped by 3 lb.-ft. (from 376 down to 373 lb.-ft.), and the E303 and Summit Racing E303+ cam traded power production back and forth (by 1 to 2 hp) until the top of the rev range, where the E303+ showed its strength.

The solid gains at the top of the rev range offered by the new Summit E303+ cam came with a small penalty in torque loss below 3,000 rpm.

Stay tuned, I plan to test the new B303+ and F303+ against their Ford Performance counterparts in an upcoming story, and if you want to hear these cams run at WOT, check out the videos up on my channel.

And there are plenty more cool 5.0L cam tests coming!

Looking at the power curves, we see that the aluminum-headed 302 produced 368 hp and 364 lb.-ft. of torque with the stock 5.0L cam. Credit the extra airflow offered by the 190cc, as-cast heads from BluePrint Engines (compared to stock E7TEs) and the dual-plane Edelbrock Performer RPM intake for much of the power production. Run with the Ford Performance E303, the power output jumped to 400 hp (399.9 hp) and 376 lb.-ft. of torque. The Ford E303 cam improved the power output by 32 hp, but the new Summit Racing E303 Plus stepped up the power gains to 44 hp, with a peak of 412 hp. It is interesting to note that the peak torque dropped slightly with the dual-pattern Summit Racing E303+ cam, but only by 3 lb.-ft., from 376 lb.-ft. to 373 lb.-ft. (Dyno Chart/Richard Holdener)
Our test motor started off as a simple 302 rebuild from Marshal Engines. Nothing fancy, just a late model, production hydraulic roller block stuffed with a cast crank, rods, and pistons. (Image/Richard Holdener)
The motor was first equipped with a stock 5.0L H.O. hydraulic roller cam, but the stock stick would be compared to both the Ford Performance E303 and the Summit Racing E303 Plus. The E303 offered .498 lift, 220 degrees of duration and 110 degree LSA. (Image/Richard Holdener)
To better illustrate what the performance cams had to offer, we equipped the 302 short block with a set of aluminum, as-cast, 190cc heads from BluePrint Engines. The heads flowed 250 cfm, which compares very favorably to the 166 cfm offered by stock H.O. heads. (Image/Richard Holdener)
To ensure adequate valve control, we equipped the BluePrint Engine heads with a beehive spring package from Comp Cams. (Image/Richard Holdener)
Because the heads were set up for screw-in rocker studs and guide plates, we equipped them with a set of 1.6-ratio, roller rockers from Crane Cams. (Image/Richard Holdener)
Though we will eventually compare the cams in fuel injected form, we chose a simple dual-plane Edelbrock Performer RPM intake for this test. (Image/Richard Holdener)
Topping the Edelbrock intake was this Holley 750 carburetor. The carb featured Percy’s external adjust-a-jet system that allowed us to dial in the AF ratio without the need to remove the bowls and swap jetting. (Image/Richard Holdener)
The carbureted 302 Ford was equipped with an MSD distributor. The timing curve supplied by the MSD distributor was locked out, meaning a fixed timing value at every rpm. (Image/Richard Holdener)
Exhaust chores were handled by a set of 1.75 inch long-tube headers that featured 3.5 inch collectors and no mufflers. (Image/Richard Holdener)
To aid the low-speed torque production, we installed these collector extensions on the long-tube headers. The extensions improved torque production by as much as 50 lb.-ft. (full video of the test is available on Richard Holdener’s YouTube channel). (Image/Richard Holdener)
After running the stock cam, the carbureted 302 produced 368 hp and 364 lb.-ft. of torque. The E303 bumped these numbers to an even 400 hp and 376 lb.-ft. (Image/Richard Holdener)
With the stock and E303 cams tested, we tore into the motor for the final cam swap. Removal of the damper and water pump provided access to the front cover. (Image/Richard Holdener)
We plan to test all of the new Summit Racing 5.0L Plus cams (E303, B303 and F303), but we started this adventure with the new E303 Plus, PN SUM-8900. (Image/Richard Holdener)
Out came the E303 and in went the new E303 Plus from Summit Racing. (Image/Richard Holdener)
Run on the dyno with the new Summit Racing E303 Plus cam, the peak power numbers improved from 400 hp and 376 lb.-ft. to 412 hp and 373 lb.-ft. of torque. (Image/Richard Holdener)

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Richard Holdener is a technical editor with over 25 years of hands-on experience in the automotive industry. He's authored several books on performance engine building and written numerous articles for publications like Hot Rod, Car Craft, Super Chevy, Power & Performance, GM High Tech, and many others.