The first is a healthy street/strip cam for a light to medium-weight/gear car, and would work with some added compression. The second is much milder, a nice upgrade from stock for snappier street performance. The engine size and breathing would determine rpm and overall effect, and the smaller the engine, the greater the characteristics will show. How's that for a lame answer?

 

looking the pics, the first cam specs I see is the one with 212 intake duration, the second has 236…..as far as differences the one with more duration will rev higher, your kind of just moving the power and up higher in the rpm range, as far as springs, both cams have about the same lift, so you could just put the cam in without worrying about binding, but if there’s not enough pressure you might have valve float issues at higher revs. You’ll need to get the spring specs of what you have now….

 

The first is what's in my GT40P right now. A cam follower seized and wiped #5 exhaust lobe. All new stuff, too. So I'm looking for a replacement that can use the same springs (Alex's Parts) that I'm already using.

 

Oops, yep, got them ordered backwards. Fixed and thanks for catching that!

 

OK...I was scratching my head thinking you had them backwards.

 

Based on lift, yes, same springs will function. Whether they will handle the higher rpm of the hotter cam would need more looking. A place to start is the suggested springs or spring spec's from the cam maker.

 

What about my current cam versus a F303?

 

I have the XE264HR-12 version with a 112 split vs 114. Along with 1.7 rockers bringing the .512 lift to .544

It revs to 6500 rpm and makes power to about 6300. Put down 319HP/ 310TQ to the wheels in my setup

I was originally gonna run this same cam on my GT40 heads with upgraded beehive springs (not sure if alex's or not) but was able to snag some AFR 165 Renegades

I might upgrade to the XE274 for just a tad more top end but the current setup works very well. I am hesitant.

 

When I bought my cam I told Comp that I had a GT40P and I wanted the biggest cam they recommend for a stock converter. I'm using factory rockers.

 

You’ll need a bit more converter with the bigger cam. If you have power brakes it might be iffy. What size engine? What gears and trans?

 

Manual disc/drum setup.

 

I asked Grok which Ford alphabet cam is closest to the XE264HR-14 I have and it said that the E303 was the nearest.

 

What are you looking to accomplish? I have a much larger engine with a cam with similar specs to the second one you show, it has a distinct idle at 800 rpm, it runs hard to 6K, but I also have the compression to match the cam, ported heads, a 5 speed and 4.11 gears to take advantage of it. If it had an automatic it would need a 2500 stall converter……It’ll run good, but to get the most out of it you’ll want some other pieces….nothing in between that looks good to you, something with around 220 duration on the intake?

 

I bought the engine used and installed new cam, springs, lifters, pushrods, oil pump and timing set. The cam is the one in the top pic, the Comp XE264HR-14, and one of my new Melling lifters killed #5 exhaust lobe. I'm trying to find a used roller cam with similar specs that will be appropriate with the spring set in the engine so I don't have to spend another $600.

 

Yesterday, I spoke with Alex's parts about which cam I could substitute for the Comp. He suggested the F303 Ford cam as very near in spec to the existing and requiring no further changes to my spring setup. Anyone have an opinion?

 

I think you’ll need a higher stall converter with that cam too…..you’d be going from 212 degrees on the intake to 226, that’s quite a jump….

 

How would the car behave with the stock converter?'s

Grok's advice:
Determining the "biggest" camshaft you can use with a stock Ford C4 torque converter depends on several factors, including your engine setup, vehicle weight, rear gear ratio, intended use (e.g., street driving, cruising, or performance), and how much compromise you're willing to tolerate in drivability. The stock C4 torque converter typically has a stall speed in the range of 1,600 to 1,800 RPM, which limits how aggressive a camshaft you can run before idle quality, low-end torque, and overall street manners suffer significantly. Let’s break this down using Ford’s "alphabet" camshafts (e.g., B303, E303, F303, X303) as a reference.
Key Considerations

1. Stock Torque Converter Stall Speed: A stock C4 converter doesn’t provide much slip, meaning the engine needs to produce usable power at lower RPMs to avoid bogging down when you put it in gear or accelerate from a stop. A camshaft with too much duration (especially over 230° at 0.050" lift) will push the powerband higher than the converter can handle effectively, leading to sluggish performance and potential stalling.
2. Ford Alphabet Cams: These are performance hydraulic roller camshafts designed by Ford Performance for small-block engines (e.g., 302/5.0L). They’re labeled alphabetically (B, E, F, X, etc.), with increasing duration and lift as you move up the alphabet. Here’s a quick rundown of their specs at 0.050" lift:
   • B303: 224° intake / 224° exhaust, 0.480" lift (with 1.6 rockers), 114° LSA
   • E303: 220° intake / 220° exhaust, 0.498" lift, 110° LSA
   • F303: 226° intake / 226° exhaust, 0.512" lift, 112° LSA
   • X303: 286° intake / 286° exhaust, 0.542" lift, 112° LSA (advertised duration; actual at 0.050" is ~224°/224°)
3. Camshaft Duration and Idle Quality: As duration increases, the engine’s idle vacuum decreases, and the powerband shifts to higher RPMs. A stock converter struggles with cams exceeding ~220-230° duration at 0.050" because the engine won’t make enough torque below the stall speed to move the car efficiently.
4. Vehicle Setup: A lighter car with steeper gears (e.g., 3.73 or 4.10) can tolerate a slightly bigger cam than a heavy vehicle with tall gears (e.g., 2.73). Without knowing your specific setup, I’ll assume a typical street car (e.g., Mustang or F-100) with a 302 and moderate gears (3.23-3.55).

Analyzing the Alphabet Cams with a Stock C4 Converter

• B303: With 224°/224° duration, this cam is on the upper edge of what a stock C4 converter can handle. It’ll have a noticeable lope at idle and reduced vacuum (around 12-14 inHg), but it can work decently in a light car with good tuning (e.g., bumped-up initial timing to 14-16° BTDC and a carb with adjustable idle circuits). Drivability will be compromised slightly, with some loss of low-end torque, but it’s manageable for casual cruising.
• E303: At 220°/220°, this is slightly milder than the B303 and a better match for a stock converter. It still lopes but retains more low-end usability. This is likely the sweet spot for a stock C4 setup if you want a noticeable performance bump without needing a stall converter.
• F303: With 226°/226°, this cam pushes the limit further. You’ll feel a significant drop in low-end response, and the stock converter will struggle to get the engine into its powerband (likely starting around 2,200-2,500 RPM). It’s doable, but expect bogging off the line and a rougher idle (10-12 inHg vacuum).
• X303: This cam’s advertised 286°/286° duration is misleading—actual duration at 0.050" is closer to 224°/224°, similar to the B303 or F303. However, its tighter LSA (112°) and higher lift make it feel more aggressive. It’s too much for a stock converter; Ford recommends a high-stall converter explicitly for this one.

The Verdict
The E303 (220°/220° at 0.050") is likely the "biggest" Ford alphabet camshaft you can reliably use with a stock C4 torque converter while maintaining decent street drivability. It offers a lopey idle, improved mid-range power, and works within the stock converter’s 1,600-1,800 RPM stall range, assuming proper tuning. The B303 (224°/224°) is a close second but starts to stretch the converter’s capability, especially in heavier vehicles or with tall gears.
The F303 and X303 are too aggressive for a stock converter unless you’re willing to accept poor low-speed performance and potential stalling issues. Ford Performance even notes that a high-stall converter (e.g., 2,500 RPM or higher) is recommended for the F303 and X303 with automatic transmissions.
Recommendations

• If you’re set on keeping the stock converter, stick with the E303 for the best balance of performance and drivability.
• For anything bigger (e.g., F303 or X303), you’ll need a higher-stall converter (2,500-3,000 RPM) to match the cam’s powerband, especially if your camshaft calls for it like the user in the search results with a 2500-stall recommendation.
• Pair the cam with good ignition timing (e.g., 12-16° initial, 34-36° total) and a carburetor tuned for low-RPM response to maximize compatibility.

If you share more details about your setup (engine, gears, vehicle weight, etc.), I can refine this further!





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Well, what typically happens is it makes the car unpleasant to drive if you don’t have enough converter. The larger cams will require a higher idle to be somewhat smooth. With a tight converter it drags the motor down at idle and creates heat in the transmission. I imagine your original cam probably idle nicely Between 6 and 700 rpm, and when dropped in gear still held that idle. Now imagine moving the power and away from a low rpm to something that comes in at 2500 or so. It will probably be happier idling at 800 or so. Drop It in gear with a tight (lower stall) converter and you’re gonna get a clunk as the driveline engages, and since it’s loading up,the engine it might not maintain that idle like the lower duration cam would…..might take a foot on the brake and one slightly on the gas……give it the gas to go and it’s struggling to get to the rpm where it makes power. With the higher stall converter that mostly goes away, but the do create heat also….and as long as your doing that might as well get some gears in the rear to really wake it up…..

 

I have a 3:50 ls, 9"

 

I would look at it from the other direction, to be sure you are comfortable with the stall effect compromise. Do not mistake that TC stall is always a compromise, and you need to know what that is for your situation and goals. The TC stall is a critical factor in the package that can fully enable it, or create a dog.

For example, drag-only cars typically choose stall at or a hair below the engine's peak-torque rpm. This shoots the engine directly to max performance range for launch. Once it's rolling and speed increases, stall is irrelevant. And don't overlook that fact that a well-built high-stall converter will generally drive and feel like a stock one, until pushed hard.

My personal approach for street/strip is to aim towards engine peak-torque, and back-off only if required for other reasons, such as highway cruise lower than stall. Compromise. Since you seem to like Grok, try this: https://grok.com/share/bGVnYWN5_3e514559-133d-47d0-856a-cea7975fc9a5