HELP! Transfers, primary vs secondary (open quad)

[UltraSwine]

Greetings. I'm a year-long lurker, this is the first time I've had a question that isn't answered by a little searching.
Long story short, this is a transfer port question. More or less. I was running an 49mm AM 390 jug on my '04 MS290 and it fried. Now, I am putting the original Mahle 46mm jug back into service. While I have worked the Mahle (290 46mm) jug for squish (chamber,milled base, bearing/seal saddles) the 46mm MS290/029 transfers have me baffled. "390" jug has larger transfers, I get it. In the "390" the primaries (exh side) are slightly larger than the secondaries (int side). No shocker there. But... the 290 jug is different, the primaries are noticably smaller than the secondaries. Why?
After dropping the jug more than 0.040" the transfers will need to be raised. Should I open the primaries more like the secondaries while I'm in there? Or, is there any benefit to having tighter primaries? Open quad port, BTW.
After reading "theories" on this site until my eyes bleed, I can't figure out how it would matter how a saw gets happy with one configuration over another AS LONG AS it gets the air/fuel it requires. But... I'd like to know whether or not primary vs secondary "volume" makes any difference if the engine gets what it wants.
Thanks in advance.
Ultraswine

 

[drf256]

Good morning.

The primaries function to sweep the burnt charge off the piston crown by pushing fresh charge towards the intake wall. Yes, they are closer to the exhaust.

Because the piston if falling while the transfers crack open, there is a dead space near the intake wall of spent charge.

The secondaries clear that area and help to lift the fresh and spent charge towards the intake side chamber.

The secondaries open after the primaries for the above reasons. Because they open later, there is less case pressure left when they do. How does one achieve the same speed out of a tube with less pressure? Decrease the size of the tube ID. Like when you put your thumb over the end of a garden hose without a nozzle.

Hope this helps.

 

[Ketchup]

Sounds like an EPA design thing to me. I would take them both up even. Aim the secondaries higher. You could try to make the Primaries larger, but usually that just slows the transfer velocity.