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PostPosted: Wed Jan 13, 2021 9:16 am 
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Joined: Mon Oct 29, 2012 2:39 pm
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Same as KV, but the bigger thing with 4V heads - IMHO at least - is raising the floor of the intake with inserts (tongues) to reduce the port volume and provide a better path to the valve seat. Just increasing the valve size may do a little for low lift flow, but after that I think it's port configuration.

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PostPosted: Thu Jan 14, 2021 12:28 am 
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Joined: Fri Mar 01, 2013 9:58 pm
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1EFF100 wrote:
So what you guys are saying is, leave the 2.04 and 1.65 valves alone and run them? You can't install the 2.19 and 1.71 valves and blend the port to valve pocket area and have, essentially, a factory big valve 4V head?

I would really like to see some flow numbers between the small valve open chamber 4V heads and the big valve 4V open chamber heads.


If you are replacing the valves with a set of single groove stainless units then Ferrea make a 2.07 and 1.65 set to suit . They are about perfect for a 2V head.


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PostPosted: Thu Jan 14, 2021 8:18 am 
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Joined: Tue Nov 06, 2012 12:02 pm
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1EFF100 wrote:
So what you guys are saying is, leave the 2.04 and 1.65 valves alone and run them? You can't install the 2.19 and 1.71 valves and blend the port to valve pocket area and have, essentially, a factory big valve 4V head?

I would really like to see some flow numbers between the small valve open chamber 4V heads and the big valve 4V open chamber heads.


Leave the current valve sizes is what I would do. You can install the larger valves, but you won't see much of a gain by doing so. And there are better heads out there that flow higher with smaller valves then what you have, so the valve isn't always the restriction.

Like falcon67 alluded to, the shape of the port is just as important as valve size. Aftermarket heads raised the port ceiling and filled in the floor for a reason.

I don't know of anyone who has said flow numbers with stock ports to show an apples to apples comparison. But if you find some, I'd love to see it as well.


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