I don't have the money to go that way with my builds! The other trick with that TK L20 head was moving it across on the block to unshroud the valves in the bore. It was for a Sport Sedan running about 14:1 and e85 (basically alcohol). But yes, his 120bhp/l is an absolute top effort for a NA 2v full race motor!

I don't really understand what your asking - I assume "wonder if these chambers work just as well for better boost numbers than H89 chambers" means for turbo engines? Anytime you improve flow, it's obviously going to help, but if TK's customer was running a turbo engine, I doubt they'd have bothered going to these lengths to extract every last bit of flow out of the head. It's just not as important in turbo applications.

It's only important if you're racing to win

not important is not what I said...

in U2L Sport Sedans you're up against modern 4v engines. If you're going to compete with them using a 2v engine all those last little one-percenters matter ALOT! In a turbo engine, the little differences will barely register by comparison with something that relies on natural aspiration.

be careful encouraging Alcohol consumption there are kiddies as well here :)
The A series chambers seem to be already on the centre of the block so a surprise L series chambers arent. For turbo boost I just wonder if these chambers make a difference in extracting the most possible as it was great to see Sykines car come close to the 1.8 bp 16v turbo engine in that Mazda 808 which was a higher capacity class winner. Its interesting to see what the A & L series can achieve even today

TK has done a bunch of heads and if you search on performanceforums.com (I have been in a cave for over 12 months mind you, don't know what anyone is up to any more) and he doesn't mind sharing a bunch of tech advice/experience. He's done more than a few turbo heads. In my words (not his, so don't take this as gospel) with turbo setups you can tend to look at different port volumes vs NA, sometimes larger actually works better. Air is a gas, but it also moves partly like a liquid (poor description of it to say the least) and it's (obviously) compressible so the rules don't apply quite the same way..

You'd generally want slightly wider exhaust seat contact areas, even at a small detriment to flow, since a turbo engine will deal with more exhaust gas, and it's effectively 'trapped' in there behind the turbine, so to speak, so the exhaust valve has a lot more heat energy to deal with and a wider seat means more contact more conductivity and thus more cooling whilst it's on the seat.

Combustion is still combustion, so you still want to squeeze it into a ball like shape, so ideally it'll still be a combo of bathtub-ish shaped chamber, give or take, and a piston dish to match that bowl shape so there's still good quench and good mixture motion at/near TDC for optimal burn (though the burn will go for longer than an NA engine by virtue of the fact there's much mor in there to burn to start with and that extra mass of gas means it'll still have useful pressure when the piston is relatively much further down the bore). The difference would be that you'd want the overall dish volume/chamber volume to be a bit larger vs the NA engine.

Of course with NA engines, you can or might get to a point where it just isn't practical to have that shape and still get anywhere near enough compression for a given fuel/cam duration/etc and so you have to start compromising a little on piston dish (or perhaps crown) shape. But that's racing engines, everything is a compromise of some sort, because you can't run infinite rpm, infinite valve sizes, infinite port flow etc etc etc.

If I was starting from scratch in a racing category and it allowed an unrestricted turbo on a smaller engine capacity, in general that's where I'd tend to look, though it won't necessarily be cheap. I'm sure they'd try and mandate that 'unrestricted turbo intake' engine capacity to the point it became competitive rather than dominant, but the last I looked that's probably where I'd go. If not then last I looked some of the sr20ve engines were apparently getting fairly awe inspiring power per litre. I think Allen engineering (no contact with them personally) did some 1 litre possibly bike sourced engines with high boost in ip or possibly sports sedans but don't quote me on it. When it comes to A-series stuff, last I checked, nobody was in Simon's league (and again, I've been out of the loop for a long time now!)

Going back several years, Datsonovic and Yatala Head Works have had very good power from turbo A series too.
EDIT: oh, and Finn!

Just looking at the turbo chamber and piston using your terms Jmac and from what Ive seen so far so can be wrong! but would you say if someone is looking at under 7500-8000rpm its better to have small capacity David Vizard favored chambers as TK uses but making up for the high comp using dished pistons?. The dished pistons are a little heavier but better for heat dissipation and stay strong at these revs while the inlet valve providing it gets enough lift could be better deeper into the head so it creates a funnel like shape for the mixture rather than level with the exhaust valve? eg. creating less turbulence in the middle of the chamber.

Meaning the seats would need to be cut deeper into the head for the inlet only just enough to get a taper there to help the seat.

Here is a basic cross section of what Im trying to trying to convey
blue is the inlet valve deeper set within the chamber exhaust is red
I know there is more to the chamber but just wondering what if atm
as I understand the need to get the mix towards the centre but also
concerned on the combustion balance for that ball shape at tdc
without resorting to the more ideal hemi chamber.
There would be more bias or guided mixture on the outer edge of the
inlet valve while the centre area only has a taper halve the length.

Attach file:

---

  COMBUSTION SHAPE.jpg (15.82 KB)

Hemi chamber is not ideal. It's very good for high velocity airflow, but really poor for part throttle airflow. For naturally aspirated it has a poor compression ratio unless using a massive dome which is a tradeoff

Chrysler doesn't even use a hemi chamber in their HEMI engine!

Yep, even the hemi 6 didn't have hemi chambers, they were polyspherical. They flowed well, had some swirl (port size arguably too big for a stock a-b streeter, almost irrespective of cam choice at the milder stages, they all get a big kick in the pants around 3100-3500rpm as the port sizes finally get up enough velocity and you feel like you've got about double the torque by 3000rpm as you have at 2000 no kidding). and practically zero quench, which was to some extent an issue. It's a big reason the aftermarket heads go with the more conventional chamber shapes.

D - I'll try and tackle your question on the weekend, it'll be a bit bigger write up than I have time for tonight. And whatever I type, remember, it's only to the best of my knowledge, not written in stone!