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Discussion Starter · #1 ·
Hi, I need help. Can I just switch out the sohc 3v heads for dohc 4v heads if they are also from a 4.6 modular engine? If I can, to me that sounds way better and gives me more potential to build on but I don't know.
 

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Short answer, no. Long answer, yes. They have the same bore spacing and mounting bosses so yes they will swap. However, you’d have to swap the intake, injectors, lock out the cam phasers, etc. and all of that to gain nothing and lose torque. You’re better off boosting the 3v.
 

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Discussion Starter · #3 ·
Short answer, no. Long answer, yes. They have the same bore spacing and mounting bosses so yes they will swap. However, you’d have to swap the intake, injectors, lock out the cam phasers, etc. and all of that to gain nothing and lose torque. You’re better off boosting the 3v.
Extra cams and valves, why would it lose low end torque with extra air flow? And I assumed cams would give it more torque as well.
 

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Because you have lower velocity at low engine speeds without and without vct and charge motion plates, you lose torque. Yes cams can add torque depending on the profile but then again a profile ground for torque will lack top end, where having all that port volume would really shine.
 

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Discussion Starter · #5 ·
Because you have lower velocity at low engine speeds without and without vct and charge motion plates, you lose torque. Yes cams can add torque depending on the profile but then again a profile ground for torque will lack top end, where having all that port volume would really shine.
Is there some way to fix that? I want to one day get a twin turbo setup and I assumed more valves and cams would help. I'm not sure what to do since the 3v sohc engine is that strong of an engine compared to a lot of others
 

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Is there some way to fix that? I want to one day get a twin turbo setup and I assumed more valves and cams would help. I'm not sure what to do since the 3v sohc engine is that strong of an engine compared to a lot of others
What is your end goal? A 4v swap isn’t worth it in an s197.
 

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I'm not sure tbh, a daily that is also super fast and good for the track. It's just the s197 3vs are kind of weak compared to others, even boosted.
Why do you say that? There are a few guys I know running 500 hp 3v’s that are pretty quick. A coyote, for example, is a better power plant to start with but boost really evens things out. And no need for 4v heads when a 3v flows almost the same.
 

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Discussion Starter · #9 ·
I just assumed it would have more potential with more cams and valves if I boosted than 3v. And I know they can be built pretty good but nearly maxed out NA can get passed up by a coyote with some bolt ons
 

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I just assumed it would have more potential with more cams and valves if I boosted than 3v. And I know they can be built pretty good but nearly maxed out NA can get passed up by a coyote with some bolt ons
Yeah they do flow a little more but it’s not that much more. The coyote is a different story though. For what you want, boost is the way to go. A coyote swap is another option but is more involved.


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I like to mention that 3v works because it has VVT, 4v flows same or better without. It is mechanically simpler and and you can time both cams. If goal is big hp, 4v is better.
 
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