What to do when valves are on the wrong side of the cylinder?

[BLSTIC]

So I just watched DV's latest youtube upload and it was enlightening to say the least. I finally understand what port bias is about. The contents of the video also described how the location of the valve/port in the cylinder also affects bais (it wasn't directly stated, but I realised it for the the first time while watching), and how too much airflow on the short side at high lifts can disrupt overall flow.

The problem is, the non-crossflow head I'm doing my latest thought exercise on is exactly wrong AND has a shallow port angle to boot. This is a 12-port Holden 6. The big problem is that the natural airflow if you put valves in this spot would be vaguely downwards in this picture, and the ports go up. The air needs to turn more than 90 degrees from where it would want to go given the location of the valves, and the bulk is coming from the short side.

holden6combustion.jpg

This is the only cutaway I can find of the inlet port. Naturally it's already a carved one so I can't see the shape of the original. Assume that the water gallery ISN'T open to the inlet port though...

holden6inlet.jpg

Top down view, showing significant material available remaining despite previous carving already taking place. Could probably bias port a lot, if it would help

411.jpg

The head can be moved 1-2mm, moving the valves away from the cylinder wall, which helps a little. Apparently a max effort head is around 230cfm, but 210cfm is closer to a normal 'extensive' port job on these. So 300-ish hp, 202ci 6 cylinder engine.

What would you guys do to get the most out of this head? Would a steeper valve seat angle help? There is no real 'application', it's just a thought exercise.

But my thoughts are that if I was going for a street engine and around 230-250hp I'd fill the inlet floor a not-insignificant amount and make the port as downdraft as I could, chasing, as DV would put it, maximum port energy.

Similar story on the exhaust. Following Calvin (exhausted)'s numbers and extrapolating downwards, I'd be looking at 1 3/8" pipe off the head (which is roughly the size of the stock hole, maybe a teeny bit smaller), so the exhaust port itself could have the roof raised and the floor filled with port plates.

[mag2555]

Port bias would certainly help, but even with heads that have a 14 degree inclination angle no less whatever this shallow head is , that is why the short turn needs to be as wide as possible within the frame work of making the valve bowl throat the minimum port area and where peak velocity within the port if your intention is to shoot for max high rpm power in a narrow range.
At least that head has a decent amount of short turn height to lay back, but another trick to slow down short turn velocity is to not have a complete arc, but to have a straight section that when done right will slow down the velocity.


The detail to getting this to work for you is that the straight section must be parallel to the valve inclination and about .100” to .150” tall dependent on how low on lift the flow separates off the crown of the floor.

If you have ever seen a iron Ford 2bbl or 4bbl Cleveland head, Ford chose to take this to a extreme!

Sometimes though if you do not have enough mule ports and or heads to play around with as the case may be it’s just better to get the geometry between the valve bowl throat and short turn arc pretty good and then settle for a smaller window area at the crown of the short turn so that the air volume level needed to send the port into turbulence can not take place.

Also I can tell from the chamber shot and for sure the cut away that the Chamber even with that shallow inclination angle is very shrouded on the long side !