Should I port my 351C 4V heads?

Hi everyone - I just bought a 1971 Mach 1 Mustang. It has 351C 4V and 4 speed, and 3.25 Trak-Loc gears. I will be putting a new cam, intake and headers on the engine.

I will have the heads off so I thought that I would get some mild porting done on the heads while they were off; some bowl work, a little short turn radius smoothing and slight shaping of the valve bosses. But the more I read about getting this work done the more leary I became of doing anything. I actually read one engine builder who did a back to back dyno test on a street/strip motor and made the exact same horsepower after porting the heads. I can't find any real before and after head porting dyno tests. Let me know what you guys think. Thanks!

BTW The cam going in is a solid flat tappet 288/292 advertised duration, 228/234 @ .050 duration and .535/.553 lift. 114 LSA. Pretty mild stuff, just a fun street cam.

Luc Feilla said:

BTW The cam going in is a solid flat tappet 288/292 advertised duration, 228/234 @ .050 duration and .535/.553 lift. 114 LSA. Pretty mild stuff, just a fun street cam.

Click to expand...

Seems you answered your question...

Here ia a real world non ported 4V headed motor:

https://7173mustangs.com/threads/sh...-very-good-dyno-conversation-on-tuning.45128/

My opinion Luc: With your engine setup and your intended use, you will gain nothing worthwhile with porting. Apply your efforts on a good tune and a high quality valve train setup. Then enjoy those factory Cleveland ports!

Depending on your end goal. If it is just for cruising, then don't waste your time. If you want more power because you have a use for it, like racing or simply going fast from light to light then it may be worth it. However, unless you really have a reason to keep the stock heads, I suggest you invest in a good set of aluminum heads like CHI heads. It may cost a bit more but at least you don't have to deal with the unknown results from whoever is doing the port job. If you really still want to port your heads then find a reputable Cleveland head porter. I have a need for power due to my racing hobby. I first went the direction of porting the heads with some small gains. After some time I bit the bullet and went all in with a set of CHI 4V heads and that's when the gains really made a huge difference.

Thanks guys for the replies. I think I won't port the heads. When I say port I really mean just smoothing out the exhaust short turn radius and the bowl areas a bit. But it really doesn't seem worth it given the generous amount of air these heads flow and my smallish solid flat tappet cam. Even my head porter send not to bother given that I just want to go fast light to light and do the occasional Historic auto course HPDE events.

tony-muscle - you are correct, of course. The aluminum heads are the way to go for power; the improved designs and technology of the past 50 years make them much better. However, I am nostalgic (anachronistic?) and can't part from the old iron slugs!! I know it doesn't make perfect sense but I am going to stick with them

I'm NO engine guy by a looong shot, but I didn't see mention of installing rocker studs if you're going with a solid flat tappet cam.
If I were redoing my motor, I'd go with a good set of roller cam and lifters and a very good timing chain set.
Just my 2 cents worth.

I also feel there is nothing to be gained by porting. And you will just hurt the value of the heads if you do. My stock heads make more than enough power for me!! Good luck!!

For what you are doing it is not worth it. Concentrate on good valves, 5 angle valve job, and appropriate valve train components. Get as close to Zero deck on the pistons/block. I'd suggest breaking the cam in with just the outer springs. Yes, it is a PITA but, worth the effort in my opinion. Chuck

Sorry for overdoing this but I am having fun testing AI with ChatGPT. I think this answer is actually very good.

Should I port my Cleveland 351C 4V heads?

ChatGPT said:​

Porting your 351 Cleveland 4V heads can certainly improve engine performance, but whether you should do it depends on your specific goals and the rest of your build. Porting increases airflow to the engine, which can help improve horsepower and torque, especially at higher RPMs. Here’s a breakdown of the factors to consider:

Benefits of Porting Cleveland 4V Heads:​

1. Increased Airflow:
   • Porting improves the intake and exhaust pathways, allowing more air and fuel into the cylinders and more exhaust gases out. This means your engine can potentially breathe better, leading to more power.
   • The 351 Cleveland 4V heads are already known for their large intake valves and good airflow potential, but porting can help them achieve their full potential, especially at higher RPMs.
2. High RPM Power:
   • The Cleveland 4V heads are designed for higher RPM performance, and porting can unlock even more top-end power, which is beneficial if you plan to rev the engine higher or are building it for performance (like drag racing or road racing).
   • Ported heads can improve the flow in the mid-to-high RPM range, where a lot of engines, including the 351C, benefit the most.
3. Better Combustion:
   • Porting can also help improve combustion efficiency, which can lead to gains in both power and fuel efficiency, as it optimizes the air/fuel mixture entering the cylinders.

When You Should Port Your 351C 4V Heads:​

• High-Performance Build: If you’re building the engine for high-performance applications (like racing, autocross, or track days), porting can help unlock the potential of the 351C’s large valves and high-flow design, allowing the engine to perform at its best.
• High RPM Focus: If you plan to push the engine to higher RPMs, porting will help it breathe better at those elevated speeds, improving horsepower and throttle response.

Potential Drawbacks:​

1. Cost and Time: Porting heads is a labor-intensive and costly process. Depending on how much material needs to be removed and whether you’re doing it yourself or having a professional do it, it can add up. Plus, there's the potential for errors, which could damage the heads.
2. Throttle Response at Lower RPMs: If not done correctly, excessive porting could lead to a loss of low-end torque. This is because too much porting can create a mismatch between air volume and air velocity at lower RPMs, resulting in poor throttle response and lower efficiency in the low-to-mid RPM range.
3. Overkill for Mild Builds: If your goal is a mild street build for daily driving or moderate performance, porting might be overkill. Stock Cleveland 4V heads can still provide strong performance without porting, especially if you're sticking with lower RPM ranges or mild upgrades.

Things to Consider Before Porting:​

• Your Engine Build: If you're planning on running a high-compression, high-lift camshaft, a performance intake manifold, and large headers, porting the heads will complement those upgrades. If you're sticking with stock or mild performance parts, the gains from porting may not be as noticeable.
• Head Type: The Cleveland 4V heads are already designed for high airflow, and while porting them can increase that potential, they are more beneficial for high-revving engines rather than low-RPM street use.
• What Kind of Porting: You can choose mild porting (a little cleanup and smoothing) or extensive porting (a full modification of the intake and exhaust ports for maximum flow). Mild porting may be sufficient for street use, while extensive porting would be better for a full race engine.

Conclusion:​

• Yes, port your 351C 4V heads if you're aiming for higher horsepower and high-RPM performance, especially if you’re building the engine for racing or performance applications.
• No, don’t port them if you’re looking for a street-friendly build with good torque and drivability at lower RPMs. In this case, you might be better off sticking with stock heads or mild modifications.

It really depends on how you plan to use the engine. What kind of performance are you aiming for with your build?