Wrapping up 68' 302 4V with new CNC port

[mummert]

https://youtu.be/lESoEcvyXME

[Joe-JDC]

Here is an intake to match the heads. Difficult to get the flow up on the lower plane, but can be made to work well with lots of work and time.   Joe-JDC

[mummert]

Looks great Joe. Hope your having fun being retired. 

[frnkeore]

How much does the shaping of the short turn increase flow?

[pbf777]

         Joe,
   
         Perhaps you've done these cast iron intakes before, so I might not be helping you any, but when I've tried hard on these I found that removing the separations that create the "4-hole" carburetor pad in the pairings front to back of the upper and lower, but maintaining the separation left to right of the upper to lower, making it look more like the later '60's and "repop" aluminum "Cobra" intakes with the ovals, works well in increasing the plenum areas and in gaining better access to the transition in the vertical plunge borings to horizontal runner entries.   

         Scott. 

[mummert]

How much does the shaping of the short turn increase flow?

Quite a bit.  These heads are very small over the short turn so the speeds are very high.  If the short turn is wrong this head will plateau off at .450" and the swirl will go through the roof.  So look at the flow sheet at .450 and draw a straight line to .600 and that is what the flow will be. The swirl will jump about a 1000RPM so low 3000's.  When the short side is poor the flow zone shuts down and creates a nozzle.
  Short turns help with valve lift.  If you always run cams with .450" lift your shorturn skills don't need to be spectacular. You may even see some small mid range power losses with a swoopy short side and a low lift cam.
Its all about .25 L/D ratio.  Below that the curtain area is is controlling flow, so the port velocities are lower. Things stay happier.
Once you get over .25 L/D the flaws show up fast

[Joe-JDC]

I've removed the hole dividers in several types of intakes and helped with the flow distribution and balance.  Boss 302 and Boss 429 intakes benefit with a dual plenum over the four holes.  428CJ does, also. The 312Y intake really works much better with dual ovals.  Joe-JDC

[frnkeore]

This is what I got, in comparison to yours, when porting a C6, smog head. I was paranoid about what to do with the short turn. There were horror story's about breaking into water and I couldn't see that area very well either so, I just left it alone. I widened the throat and blended it into the short turn, trying to keep it's transition radius the same as the ST. As I remember, the ST has a radius of about .5 and looked fairly tangent to the port floor and I was concerned about messing that tangent area up.

[mummert]

It looks pretty normal for no short turn work.  I think a 210@ .500 lift could be had with decent short turn work.  Some cross sections would have to get opened up if you wanted bigger numbers.  The short turn has some metal in it , 289 heads are pretty thick.
 You want to limit overhang on the short turn.