well i was looking at the alpina heads and working off what they had done, i cant at this point guarantee that alpina didnt pull some little trick that makes their hemi work, but even if they did then we just dont know about it atm so cant replicate it an we are in the same boat as before.
the big (and untested) benefit seems to be from the valve seat and throat, and i have a few suggested designs for those.
I dont like the cut outs on the MM pistons due to the size of cavity they leave in the combustion chamber, they are nice places for unburned mix to hide in and create bad emissions, they also are going to be the last place the fuel mixture burns due to quenching of the mixture and their distance from the spark plug (especially on the exhaust side)
What this will cause is a pocket of unburned fuel in a relatively hot area of the engine (as the piston is a hot bit and especially on the exhaust valve side where the red hot exhaust valve extends into the pocket)
This pocket of mixture is also under a lot of pressure and as we know hot fuel under enough pressure detonates.
basically in a high comp engine its a recipe for detonation.
i take this fron their site.
Too much advance
Some folks also tend to think that running more advance will make their car go faster. The combination of Surface Turbulence and high compression (10.0:1) creates a rather fast burn cycle in the combustion chamber. The timing specifications listed in our tuning guide are for optimal (?) performance and will sound rather RETARDED.
notice also on the m20 engine spec sheet how all of the deep valve pocket pistons are 10:1 and have the suggestion above and the engines using the bowled normal pocket pistons are happy at 10.5:1 and 11:1.
also considering all of their engines are full balls out built motors they make quite weak figures.
all of then have custom pistons, lightweight rods, a "hi-flow 16% better head" and 280+ duration cams, but give the following results.
2822cc - 205hp giving 72.64hp/l for $6495 that a nice $31.68 per hp
2926cc - 220hp giving 75.18hp/l for $8295 that a nice $37.70 per hp
3121cc - 230hp giving 73.69hp/l for $8295 that a nice $36.06 per hp
2926cc rally - 225hp giving 76.89hp/l for $8489 that a nice $37.72 per hp
2966cc rally - 230hp giving 76.76hp/l for $8695 that a nice $37.80 per hp
3121cc rally - 240hp giving 76.89hp/l for $8995 that a nice $37.47 per hp
dont forget that sump modifications (baffling and windage tray) are $750 extra
now consider we are getting 210hp for about £2k in the uk using stock pistons at non ideal height, stock 320 rods, a 270 cam, a stock head, no balancing.
starts to make the above look a bit shite. just think what going turbo would yield for that nine thousand dollars.
if this sounds a little hard on metric mechanic then, i wont start on some of the other things in there catalog that make no engineering or mechanical sense.
(i could of course give it to some of the real cynical bastards at the uni to rip to bits but i dont think they would get past the belt breakages, head bolts or surface turbulence sections of the catalog without imploding.)
). I get my degree results tomorrow 
