3V heads (was Re: [DeTomaso] 2V heads0

[Ken Green]

Dan,
   
        Are there any good papers that discuss CFM and air velocity in the ports?  My Yates heads have pretty small ports, but flowed about 340 at 600 lift.  The guy who rebuilt them for me thought the port shape where the port turns toward the valve was a big deal, and the smaller port has room for a more gradual turn which the air really likes.  Also, I assumed the typical flow numbers are all steady state and don't take any pulsing into account.  
   
        I don't think I properly understand the phenonena behind the poor low RPM performance of 4V heads.  I know the smaller ports have higher velocity, and for some reason that's good, but I'm not exactly sure what's going on.  Is it actually a tuned manifold effect?  It doesn't seem like the runners are long enough.  
   
        I can see how higher exhaust flow velocity should help scavenge a little more exhaust at the end of the exhaust stroke, is it the same thing at the end of the intake stroke?  Does the momentum of the air in the smaller runners and ports jam a little more air into the cylinder at the end of the intake stroke?
   
  Ken
   
   
  
adin at frontier.net wrote:
  Thanks for taking the time - I'm just trying to learn some stuff.

cheers,


Quoting Daniel C Jones :

>> The CHIs are winning the goodies @ EMC, but not producing lower
>> ETs. Why?
>
> I don't know for sure but my guess is the guys not improving with
> the CHI heads are starting off with well sorted 4V combinations.
> They slap on a set of CHI heads and matching intake with no other
> changes and don't go any faster. It may be that the combination
> isn't as well suited. Also, realize that 4V heads with a little
> short side radius work and good valve job flow about the same as
> the CHI's out of the box. The smaller port areas of the CHI's
> should help at lower RPM but drag racers may never operate below
> 5000 RPM. It's also possible their combinations are being limited
> by some other factor, say fuel pump flow or carb CFM or any of a
> number of things, so the potential of the CHI heads are not being
> realized.
>
> Dan Jones
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