[Steve Chryssos]

I have seen reliablity issues with all aluminum GEN 1 engines both small and big block in street applications. More so with big blocks. Specifically, I'm referring to ring seal issues (due to block rigidity) and head gasket issues (due to expansion). One all aluminum big block we built had an 11.625" deck height aluminum block. I swear you could almost see the thing flopping around like a boneless chicken!! An extreme example for sure.
That's not to say that these problems appear consistently. But way more frequent that with all iron or iron/alum engines. So you need to make sure that your engine builder knows what he is doing. Head studs, head gaskets, o-ringing. And the end user needs to appreciate the higher maintenance of an aluminum block (i.e. checking the torque of the head bolts on a regular basis)
Whereas the LSx engines have been designed from the start with aluminum castings in mind, GEN 1 stuff may be iron parts cloned in aluminum. Aluminum castings--particularly water jacketed castings--need additional ribbing.

Given the price of aluminum blocks, I personally would not consider an aluminum small block unless it is LSx based. I assure you that Stielow's shallow valve angle, raised runner, all aluminum, forged everything, fuel injected small block would cost big money to duplicate--Close to 10K in castings alone and it still does not have cross bolted mains. An LSx engine has all of those attributes and can be found growing on trees for under 10K complete. It blows my mind, too. But I get it now.

I'm not selling anything here. Just stating that if I build another Gen 1 it will be iron block'd. If I want all aluminum, it will be LSx based.