[DaveR_GT]

There is a bunch of reasons that alum heads usually make more power.

Here are some:
- Aluminum transfers more heat allowing you to run higher compression with out detonating.
- Most aftermarket heads have larger valves
- Most aftermarket heads have larger runners
- Pretty substaintial weight savings. I don't know if you can feel it or not, but alum heads sure are lighter!

I've never heard of aluminum blowing more gaskets. I think maybe aftermarket cast iron heads with port work could get you 50-60 hp but may need port work. ?? I've heard stock ported heads can get you anywhere from 35-55 hp depending on which heads and how good the flow numbers are.

I think how much hp you gain from heads or head work also depends a lot on the over-all combination... cam, intake, exhaust, etc.

You will likely notice the car running hotter also with alum heads. I suspect it is the heat transfer thing. I don't thing there are many guys with alum heads that will tell you their card doesn't run hotter... This may also force you to upgrade your cooling system, like alum radiator, elec. fan, high flow water pump...

Hope that helps.
Disclaimer: I'm no expert, this is just what I know from reading and my limited experience with aluminum heads on my car.

Later, Dave