I have thought about going to iron heads just because salt water eats the living **** out of aluminum. Who wants to spend 10 grand on heads every 5 years?

There are literally hundreds of aluminum head choices on the market these days and they go from basic stock replacement design levels, to raised runner, spread port full competition heads. The only draw backs I see to iron is 1) the weight, and 2) there isn't the selection and performance design upgrade choices available like the aluminum heads, but they're getting better. I've heard a few people mention "CNC" options for aluminum heads. Well CNC machining is not limited to aluminum. Any port can be digitized and CNC machined in any head. There are lots of iron heads out there with CNC machining done. If you start looking into some racing classes that have iron-only head rules you'll start seeing some pretty darn nice iron heads with a lot of time and effort into their development. The EQ320 is a good head to start with for the BB Chev. The Dart Iron Eagle 330 is a fully CNC ported iron head. There are some aftermarket BB Ford iron heads that are some very serious competition heads. The shapes and designs of the ports and chambers are what really matters, not the material. One of the design "flaws" in the BB Chev conventional head is the size of the chamber, not only in volume, but also surface area. It transfers way too much heat and making the head out of aluminum only makes things worse. The real benefit the aluminum chamber has over most iron heads is it's design and shape which up until just recent years was a huge improvement over OEM iron heads. It wasn't the material that made it better.

Apples to oranges. An ok casting compared to a full CNC head I would expect some very nice gains.

Couldn`t agree more, especially the chamber design. I have A LOT of hours into chamber work on my heads which translated into 134cc and lowered my compression to 7.5:1 .Now that I have a chance to raise that back to 8.4:1 with flat top pistons and knowing my flow numbers tailor the cam I`m hoping for some good numbers.

Coating the pistons other than the skirts ever notice the underside of the piston crown. What is that browish build up ..burnt oil. Have experimented with coating that side with a heat barrier which reduced oil temps. Have also painted my aluminum heads to help retain some heat. Some clam just pant the front and rear cylinder areas and not the center cylinders to keep heat temps more even between middle and end cylinders.

BBC has issues with the combustion chamber width vs the bore size they were really designed for a 5.00 bore back in the 427 days.
Some engines iron factory heads ported will flow better than some of the aftermarket stuff.

I think you should join the iron head club, especially in saltwater.

Not an expert, what effect does fuel have on this debate? The reason for my question, I have some old small block chevy stuff I will be throwing together for a drive around fun car, and have debated old good iron heads versus aluminum. If running e85, does that make the fuel burn cooler? Taking some of the heat detonation problems away? I've heard you can run more compression on e85.

What detonation problems ? What heat problems ? Im still not understanding how mercury has tens of thousands of iron headed marine engines out there for several decades now, and all of a sudden theres a heat/detonation problem if you use iron lol

I would imagine ethanol would burn cooler though?

That is a good question. I see companies like AFR advertising how "thick" there decks are, and how that is great for forced induction engines. Theres no question iron is stronger when comparing them at the same thickness level. Is it possible an iron head has a better clamping force and less chance of distorsion under high pressures ? Maybe why high compression, high cylinder pressure diesel engines are still running iron heads ? I know a diesel engine can have extreme pressures and extreme exhaust temps. What do they do to keep their exhaust valves in one piece with their iron heads ?

WAG - less rpm (less power strokes per minute and more valve on the seat time), smaller valves, less cam duration (more time on the seat), etc,etc ???

I don't know diesels well, thus the WAG.