the coating on the skirt is not for heat transfer.

No, the coating allows more of the energy from combustion to be used for making power rather than heat loss/ thermal transfer. Same reason an Iron Head will make more power than an aluminum head. This also holds true for Aluminum vs Steel blocks.

That is correct. It is used for scuffing against the cylinder walls as stated. The word scuffing was used instead.of rubbing. scraping etc. more or less a non metallic contact barrier.

For what it's worth, being a old school racer from way back, I remember seeing a long engine tech talk with Bill Jenkins and he said that iron heads make more power as they retain the heat in the chamber, down side was weight and harder to port...

MT if you said it,I missed it ....What iron heads did you buy

Engine quest 320cc. They are basically the old pro topline/RHS stuff. Still cast in New Zealand foundry by masport. My head guy used to really like the old RHS/pro topline stuff, and had a pair of them to in his shop to compare. We actually saw some things they have changed for the better with the engine quest castings, although, they are for the most part, the same basic casting. I bought them bare, and installing all my own hardware.

There was an article a long time ago about aluminum heads and their ability to reduce preignition and ability to run higher compression. I can't remember who wrote the article but I think they quoted that you could run roughly 2 points of compression higher with an aluminum head than cast iron. What I think is more important with the aluminum heads is the CNC programs they have which give us superior chamber designs and optomized runner designs over cast iron. To me, that's the biggest difference between the two so you get a lot better designed head.

For instance; 4 years ago I got rid of my Merlin Grumpy Jenkins heads and installed AFR 357 CNC heads. I did not change a single thing on the setup other than bolting the heads on and I gained 3-400 rpms and the boat went from running 87mph to 92.3mph GPS verified. Then last year when I did my builds I optomized the camshaft over what I had previously and the boat went from 92.3 mph to 95.4mph GPS verified. All the while the boost levels stayed roughly the same.

Here's another article; http://www.performanceracing.com/mag..._aluminum.html

I was thinking about using those Engine Quest heads on a 509 MPI build I'm doing. The prices are really good, like $500 per bare casting.

In my case I had so much heat in my chambers aluminum heads would have been melted. All my Iron eagles needed was a valve job and clean up and back in service.
Aluminum is lighter that`s the biggest advantage to racers and why aluminum head is so popular.. extra 150 lbs in a boat makes no difference. That`s a cooler full of beer.

Marketing makes the iron head seem like old technology when that couldn`t be further from the truth.It`s not that you can run more timing with aluminum it`s that you have to.
At higher horsepower I`d rather have the strength of the Iron head.
Expansion/contraction is a whole nother story.

*edit.. I should have read all the post , looks like it`s already been covered.oops

Yes, they are. I payed a bit less than that. Actually they were 425 each to my door. They are a favorite in the truck pulling class that mandates iron head per their rules. There are quite a few guys making over 1000hp on motor with these heads, ported of course. Out of the box, they flowed 370cfm at 600 lift, and 388 at .700, .391 at 800. Keep in mind this is an as cast head, 320cc runner, with a 2.25 valve.

Ive talked with quite a few head specialists and engine builders prior to buying them, and read a bunch of posts over on yellowbullet and speedtalk, and couldn't find one negative about them. Once i got them, looked them over, had my head guy give me his opinion, he really liked them. Then once he pulled our darts off the flow bench, and started flowing them, he liked them even more.