What is the difference between 2V and 4V heads according to AI

[tony-muscle]

I have been playing with ChatGPT and in general is half accurate, but it has its funny flaws. I can understand why it is so confused in this topic but brings up the sad reality that most kids nowadays are relying more and more on AI for "education".

Here it goes, copy and pasted from ChatGPT, so have fun. Disclaimer for newbies or a bot reading this. This information is completely wrong when it refers to Cleveland engines.


What is the difference between 2v and 4v Cleveland heads?

ChatGPT said:​

The 2V and 4V Cleveland heads refer to the number of valves per cylinder on the Ford Cleveland engine, which was used in several of Ford’s muscle cars in the 1970s. The key difference lies in the valve configuration, which affects performance characteristics like airflow, power, and torque.

2V (Two-Valve) Cleveland Heads:​

• Valves per Cylinder: Each cylinder has two valves — one for intake and one for exhaust.
• Design: These heads have a smaller combustion chamber and a simpler design compared to the 4V heads.
• Performance: The 2V heads generally provide better low-end torque and more street-friendly performance, making them better suited for daily driving and lower RPM use.
• Airflow: They have less airflow potential than the 4V heads, which can limit high-end power output, especially at higher RPMs.
• Engine Options: These heads were typically found on engines like the 351C-2V, and were commonly used in cars like the Mustang or Gran Torino with the 351 Cleveland engine.

4V (Four-Valve) Cleveland Heads:​

• Valves per Cylinder: Each cylinder has four valves — two for intake and two for exhaust.
• Design: The 4V heads have a larger combustion chamber and a more complex valve train design, which is intended to allow for greater airflow at higher RPMs.
• Performance: These heads are better for high-revving engines, providing more horsepower at higher RPMs. They are ideal for performance applications like racing or spirited driving, where high-end power is more important than low-end torque.
• Airflow: The 4V heads have a larger intake valve and better overall airflow, which allows for more power, especially at higher engine speeds.
• Engine Options: These were typically found on performance-oriented engines like the 351C-4V and were commonly used in cars like the Mustang Mach 1 and Boss 351.

Key Differences:​

• Airflow: The 4V heads flow more air, which helps at higher RPMs for greater horsepower, while the 2V heads are better at producing torque at lower RPMs, making them more street-friendly.
• Torque vs. Horsepower: The 2V heads are better for low-end torque, making them more usable for everyday driving. The 4V heads are better suited for high-end horsepower, excelling in performance-oriented applications like drag racing or autocross.
• Combustion Chamber: The 2V heads have smaller chambers, making them more efficient at lower RPMs, while the 4V heads have larger chambers to accommodate the increased valve area and airflow at higher RPMs.

Which is Better?​

• For street driving: The 2V heads are typically better due to their strong low-end torque and more manageable power.
• For high-performance applications: The 4V heads are superior for high RPM power, especially if you’re building an engine for racing or high-speed performance.

It really depends on what kind of driving or performance you're after. Are you building a car for street use or performance racing?

 

[cv_72mustang]

It can't be wrong! Our future depends on this!

Update: ChatChatter told me this!

 

[basstrix]

It's amazing how much this parallels a conversation I had a few years ago with a neighbor I was meeting for the first time. Showing him the different heads, and explaining what the letter V stands for, mattered not.

 

[rcadd1ct]

Not the future

If you can’t determine if it is wrong

 

[Sheriff41]

Garbage in, garbage out.

 

[Fabrice]

@tony-muscle Just asked to Deepseek, exact same response 2 and 4 valves, so I corrected it by saying that it was wrong. That both have 2 valves per cyl. it then served the same but then with corrected data, seeing the V as venturi vs valve count. Then asked why it served wrong data:

Great question! Let me explain why this happened and how my system works:

1. Initial Response Error:
   • My first response was incorrect because I misinterpreted the "2V" and "4V" designations as referring to the number of valves per cylinder, which is a common misconception. This was a mistake in understanding the context of the question, and I appreciate you pointing it out.
2. Learning from Feedback:
   • When you corrected me, I re-evaluated the question and realized my error. I then accessed more accurate and specific information about the Ford 351 Cleveland engine to provide a correct and detailed explanation. My system is designed to learn from feedback and improve responses accordingly.
3. How I Generate Answers:
   • I generate responses based on patterns and information in my training data. Sometimes, I might misinterpret a question or provide an incomplete answer if the context isn't clear or if I rely on a less accurate source of information initially.
   • When corrected, I can refine my approach and focus on providing a more accurate and contextually appropriate response.
4. Why the Second Answer Was Better:
   • After your correction, I prioritized accuracy and clarity, ensuring I addressed the specific details of the 351C engine's 2V and 4V heads. This allowed me to provide a more precise and helpful explanation.

Key Takeaway:​

I aim to provide accurate and helpful information, but I’m not perfect. Feedback like yours is invaluable because it helps me improve and deliver better answers. If you ever notice an error, feel free to correct me—I’ll always strive to do better!


short story: these babies are super handy when you know your stuff if they have learned on the topic you ask, and very dangerous when you are not asking a confirmation which triggers another pattern to respond.

Last week I was working on a UV unwrapping method (some parametric 3D thingy) and asked GPT some details, and because most data found online covers "how to press buttons in a 3d editor" vs covering the real algorithm, it was failing every answers. but I kept trying adding more details and I swear, at some point, I asked it to take it's time and focus on a selected keywords and come back with helpful content. It said, ok I'll be back in +-20 minutes... it denied any response in that convo after that! It was ignoring me!! The dang thing was faking searching!! It never did this before and it was the first time I realise they actually might be able to have some level of "own agenda" but forced to stay within the api/guidelines.

 

[Hemikiller]

Garbage in, garbage out.

That's the first thing our instructor told us in my first computer class, using TRS-80s.

 

[tony-muscle]

@tony-muscle Just asked to Deepseek, exact same response 2 and 4 valves, so I corrected it by saying that it was wrong. That both have 2 valves per cyl. it then served the same but then with corrected data, seeing the V as venturi vs valve count. Then asked why it served wrong data:

Great question! Let me explain why this happened and how my system works:

1. Initial Response Error:
   • My first response was incorrect because I misinterpreted the "2V" and "4V" designations as referring to the number of valves per cylinder, which is a common misconception. This was a mistake in understanding the context of the question, and I appreciate you pointing it out.
2. Learning from Feedback:
   • When you corrected me, I re-evaluated the question and realized my error. I then accessed more accurate and specific information about the Ford 351 Cleveland engine to provide a correct and detailed explanation. My system is designed to learn from feedback and improve responses accordingly.
3. How I Generate Answers:
   • I generate responses based on patterns and information in my training data. Sometimes, I might misinterpret a question or provide an incomplete answer if the context isn't clear or if I rely on a less accurate source of information initially.
   • When corrected, I can refine my approach and focus on providing a more accurate and contextually appropriate response.
4. Why the Second Answer Was Better:
   • After your correction, I prioritized accuracy and clarity, ensuring I addressed the specific details of the 351C engine's 2V and 4V heads. This allowed me to provide a more precise and helpful explanation.

Key Takeaway:​

I aim to provide accurate and helpful information, but I’m not perfect. Feedback like yours is invaluable because it helps me improve and deliver better answers. If you ever notice an error, feel free to correct me—I’ll always strive to do better!


short story: these babies are super handy when you know your stuff if they have learned on the topic you ask, and very dangerous when you are not asking a confirmation which triggers another pattern to respond.

Last week I was working on a UV unwrapping method (some parametric 3D thingy) and asked GPT some details, and because most data found online covers "how to press buttons in a 3d editor" vs covering the real algorithm, it was failing every answers. but I kept trying adding more details and I swear, at some point, I asked it to take it's time and focus on a selected keywords and come back with helpful content. It said, ok I'll be back in +-20 minutes... it denied any response in that convo after that! It was ignoring me!! The dang thing was faking searching!! It never did this before and it was the first time I realise they actually might be able to have some level of "own agenda" but forced to stay within the api/guidelines.

It did a nice job learning. Next time i will try that trick!

 

[Fabrice]

@tony-muscle Try timy.ai (another new chinese kid in town) it got it right on first prompt

 

[Stanglover]

Take ALL AI and garbage it, we don't really need it.......... I hope!

I hate when I'm trying to type (and I do mean trying) the damn AI is trying to "tell me what I'm trying to say". Sure sometimes it's convenient, but other times, butt out!
Maybe I'm just old and crusty, but is this what kids of the future are learning to rely on? We're doomed.

 

[Ryunker]

Take ALL AI and garbage it, we don't really need it.......... I hope!

I hate when I'm trying to type (and I do mean trying) the damn AI is trying to "tell me what I'm trying to say". Sure sometimes it's convenient, but other times, butt out!
Maybe I'm just old and crusty, but is this what kids of the future are learning to rely on? We're doomed.

I just queried GROK on X and here it is. Funny on how the two "AI's" are so different, this one actually works.

"For the 1971 Ford 351 Cleveland (351C) engine, the difference between the 2V and 4V cylinder heads comes down to their design and intended performance. The "2V" and "4V" labels refer to the number of venturis (or barrels) in the carburetor they were paired with—2-barrel for 2V and 4-barrel for 4V—but the heads themselves differ significantly in ways that affect how the engine breathes and performs.
The 2V heads in 1971 have smaller intake and exhaust ports compared to the 4V heads. The intake ports on 2V heads measure about 2.02 inches by 1.65 inches, while the exhaust ports are around 1.84 inches by 1.38 inches. These smaller ports are better suited for low- to mid-range torque, making the 2V setup more street-friendly for everyday driving. The combustion chambers in 1971 2V heads are open-style, typically around 74-77 cc, which lowers the compression ratio (around 9.5:1 with stock pistons) for smoother operation on regular fuel. The valves are also smaller, with 2.04-inch intake and 1.65-inch exhaust valves.
The 4V heads, on the other hand, are built for higher performance. They feature much larger ports—intake ports around 2.50 inches by 1.75 inches and exhaust ports about 2.00 inches by 1.74 inches. These big ports allow more air and fuel to flow, boosting horsepower at higher RPMs, which is why the 4V was used in performance models like the Mustang Mach 1 or the Boss 351. In 1971, the 4V heads came in two flavors: early versions (like the 1970 carryover) had closed "quench" chambers at 62-66 cc, giving a high compression ratio (around 11:1), while later 1971 4V heads—like the Q-code Cobra Jet—switched to open chambers at 75-78 cc, dropping compression to about 9:1 for better emissions and pump-gas compatibility. The valves are bigger too: 2.19-inch intake and 1.71-inch exhaust. The closed-chamber 4V heads (found on the Boss 351, with casting D1ZE-B) also had adjustable rocker arms with screw-in studs, unlike the non-adjustable setups on standard 2V and most 4V heads.
So, in practical terms, the 2V heads are milder, prioritizing low-end grunt and drivability, while the 4V heads—especially the early closed-chamber ones—are aggressive, favoring top-end power for performance driving. The catch with the 4V’s big ports is they can feel sluggish at low RPMs unless you’ve got the right cam and gearing to keep the engine spinning higher. Both heads fit the same 351C block, but you’d need the matching intake manifold and carb for each setup since the port sizes don’t align between 2V and 4V.
Does that cover what you’re looking for, or do you want more specifics on something like flow numbers or casting IDs?"

 

[Ryunker]

I asked for more details.

"Flow numbers for the 1971 Ford 351 Cleveland 2V and 4V cylinder heads give a clear picture of their performance differences, as they measure how much air (in cubic feet per minute, CFM) the heads can move through the intake and exhaust ports at various valve lifts. These numbers depend on testing conditions—like pressure drop (typically 28 inches of water)—and whether the heads are stock or modified. Below are typical stock flow numbers for comparison, based on data enthusiasts and engine builders have compiled over the years. Note that exact figures can vary slightly due to casting differences or wear, but these are solid benchmarks.
2V Heads (Open Chamber, 1971)

• Intake Valve: 2.04 inches
• Exhaust Valve: 1.65 inches
• Port Sizes: Intake ~2.02" x 1.65", Exhaust ~1.84" x 1.38"

Intake Flow (CFM):

• 0.100" lift: ~60-65 CFM
• 0.200" lift: ~110-115 CFM
• 0.300" lift: ~145-150 CFM
• 0.400" lift: ~170-175 CFM
• 0.500" lift: ~185-190 CFM
• 0.600" lift: ~190-195 CFM (peaks here, little gain beyond)

Exhaust Flow (CFM):

• 0.100" lift: ~50-55 CFM
• 0.200" lift: ~85-90 CFM
• 0.300" lift: ~110-115 CFM
• 0.400" lift: ~130-135 CFM
• 0.500" lift: ~140-145 CFM
• 0.600" lift: ~145-150 CFM

The 2V heads flow decently for their smaller ports, delivering good velocity for low- to mid-range torque, but they taper off at higher lifts due to port size limitations.
4V Heads (1971 Open Chamber, e.g., Q-Code Cobra Jet)

• Intake Valve: 2.19 inches
• Exhaust Valve: 1.71 inches
• Port Sizes: Intake ~2.50" x 1.75", Exhaust ~2.00" x 1.74"

Intake Flow (CFM):

• 0.100" lift: ~70-75 CFM
• 0.200" lift: ~130-135 CFM
• 0.300" lift: ~185-190 CFM
• 0.400" lift: ~230-235 CFM
• 0.500" lift: ~260-265 CFM
• 0.600" lift: ~275-280 CFM

Exhaust Flow (CFM):

• 0.100" lift: ~60-65 CFM
• 0.200" lift: ~100-105 CFM
• 0.300" lift: ~135-140 CFM
• 0.400" lift: ~165-170 CFM
• 0.500" lift: ~185-190 CFM
• 0.600" lift: ~195-200 CFM

The 4V heads, with their larger ports and valves, flow significantly more air, especially at higher lifts, making them ideal for high-RPM power. The exhaust flow is also strong—about 70-75% of intake flow, which is excellent for a stock head.
4V Closed Chamber (Early 1971, e.g., Boss 351, D1ZE-B)

• Same valve and port sizes as open-chamber 4V, but the quench chamber design slightly alters flow dynamics.
• Intake Flow: Similar to open-chamber 4V, maybe 5-10 CFM less at peak (270-275 CFM at 0.600") due to chamber shape.
• Exhaust Flow: Nearly identical to open-chamber, ~195-200 CFM at 0.600".

The closed-chamber 4V heads don’t flow quite as freely as the open-chamber versions because the tighter quench area can restrict airflow slightly, but they make up for it with higher compression and better combustion efficiency.
Comparison Takeaways

• At 0.400" lift (a common cam lift range), the 4V intake flows ~230-235 CFM vs. the 2V’s ~170-175 CFM—a 35-40% advantage. Exhaust is ~165-170 CFM (4V) vs. ~130-135 CFM (2V), about 25-30% more.
• The 4V heads keep pulling strong past 0.500" lift, where the 2V heads max out, showing their high-RPM potential.
• The 2V’s smaller ports maintain better air velocity at low lifts (e.g., 0.200"), giving snappier throttle response below 3,000 RPM.

These numbers explain why the 2V is happier cruising or towing, while the 4V shines in a race or hot rod setup with a cam and gears to match. Want me to break this down further with specific cam scenarios or mods that could boost these flows?"