The Axial .28ci and K4.6cc are just about identical engines down to the timing profiles. The only differences betwen the Axial .28ci and the K4.6cc is the Axial engines have the leading edge of the crankshaft cut with a scoop and the crank shaft 14mm diameter has 2 oil grooves instead of the K4.6's one oil groove. The Axial engines also have carb ventri inserts (I think) so you can choose between 8mm, 8.5mm, and 9mm (I cannot remember if these diameteres are correct). Also, the Axial engines use 2piece head button and heatsinmk and you can use tubo plugs with Axials where you cannot with the K4.6
Aside from what I just mentioned above, the cooling fin pattern on the block, and the color of the heatsink, they are identical engines.
The Axial .28 overpowers and outperforms the K4.6 by a wide margin, so all of these "little" differences add up to make the Axial a better engine. Also, calling them the same engine isn't really fair to the Axial, nor is it technically correct. To me, it's like calling the LS1 and LS6 or the LS2 and the LS7 the same engines. Aside from being "small block Chevys" and having similar appearances, they are not the same engines in and of themselves. The differences between all of them distinguish them as their own and thus the same principle should be applied to the K4.6 and Axial. That's my stance on it and others should consider that as well so as not to mislead people.[&:]
You have to buy the optional turbo head button from Axial to run turbo plugs. You can't run a turbo plug with the head button the Axial comes with. Another overlooked difference, and quite significant in my opinion, is that the K4.6 exhaust port is "oval" on the inside of the block casting and round on the outside-it's necked down and likely a restriction. The Axial is round the whole way through and there is no change in port size.[8D]