There is a head gasket. Further to your questions about compression... If you are thinking of skimming the head to raise compression then note the channel in the head which leads to a drilled out bolt. this is to let gasses escaping through the geasket out without entering the cowling where they would be blown into the car via the heater system.
You can see the channel clearly on this pand 30 head
You will need to get the channel machined back in if you skim. The pic is taken from the well used site on tuning these engines:
http://pages.zoom.co.uk/blitzracing/Racing%20a%20blitz.htmRegarding the turbo idea - search the archives of the Fiat 500 club board as this road has been taken before.
http://500chat.fiat500club.org.uk/ You may have a new fix, but I think there would be real problems with the pistons though I guess you could get some forged if you can afford it. I think you may find some after market valves that could cope. Cooling the head and barrells is another problem that will require some ingenuity. Those running slightly more elegant engines like the late citroen aircoolers haven't got much further than attaching a fan to the air intake. There is already a pretty big one forcing air down the engine's throat, although the paper air fliter is a major restriction. I was thinking of making up one with a 126P fliter stripped of paper, and covered with a pair of tights!
Let us know how you get on.
