So I got to thinking about this the other day... an aluminum head is supposedly less likely to detonate than an otherwise identicle iron head because it transfers heat away faster... wouldn't coating the head with something that does not transfer the heat away as fast be more likely to get hot spots and detonate? The engineers of the hellcat said the heads are almost like the Apache head with the main difference being an Al alloy that conducts the heat away faster, will the ceramic coating really make more HP or is it just snake oil and maybe even doing the oposite of what it is supposably doing? All the NASCAR used heads and othe top tier profesional race heads I see on e-bay don't use it and they would give their firstborn child to get 5 HP so what gives?

I am now looking for a way to plate my iron heads with copper to transfer the heat away from the hot spots.

The way I see it, the heat thing in the combustion chamber is always some what of a trade off. If you are going to coat your aluminum heads to keep more heat in the combustion chambers, you might as well stay with cast iron. ALL else being equal, cast iron will make more power (IMO). BUT, they are heavy, hard to work with, prone to cracking, not pump gas friendly ( the heat thing ) - while aluminum is lighter, easy to modify, pump gas friendlier ( the heat thing ). Can you make up the HP ( reads heat ) loss by being able to run a higher CR? I would think so. I think they are well suited for a street application ( pump gas). I switched from cast iron to aluminum a few years ago. Both heads were fully ported Magnums. Had flow numbers on the aluminum heads, but not the cast iron ones. On the bench, I'm sure the aluminum ones had better numbers. There were some other variables involved and I am still sorting some shat out ( including timing need differences), but My ET's didn't change much - so far. BTW, I changed because my iron Magnums started to show some cracks between the valves. What was you question again.

Sometimes we get lost in the weeds on theory and racing parts, heat contained in the combustion chambers are why a internal combustion motor makes power More heat,more expansion, without detonation, more power When you optimize the tune up (burn and use all the fuel possible)with the fuel used you get the most power, correct I forget the melting point of aluminum and cast iron but I know you can have a race motor burn up with EGT in the 1300 F range and the same motor built with the exact same parts not burn itself up with 1500F EGT range Not trying to confuse the issue of which heads to use.

Dave, that's very good thinking. I don't have answers but maybe some ideas will trigger others.

If one is drag racing and it's over in 10 seconds or less, overheating the engine is the last thing to worry about. Keeping the heat in the chamber to do work is the goal. The same goes for dyno numbers. How long does a dyno run last? so if you want max dyno numbers, the coatings are a must.

There was an interesting article in Motor Trend about running the new Corvette on the Nurburgring. After one or two laps the engine temp got warm and the control system started limiting power. Lap times increased noticeably. What good is a high performance car if it only works for 10 minutes and then limits power?

The cats at Chrysler wanted the Hellcat to be able to crank out max power indefinitely and so they paid a lot more attention to getting the heat out, thus the use of a more conductive alloy. I don't think it is a night-and-day difference in thermal conductivity, I am not aware that different aluminum alloys vary that much. But as an engineer, I understand the concept of making choices that increase the value of a product. Why not do it on every Chrysler engine? Because it slightly decreases fuel economy, and every hundredth of a mpg is worth money. The Hellcat is limited production and losing a couple of tenths of a mpg is part of the cost of doing business.

Heat transfer is tricky stuff. Each type of transfer has its own constraints, and some are not very intuitive. For example, the heat that transfers through an item can be limited by the conductivity of the item, but it can also be limited by the heat transfer into the item or out of the item. So one could use pure silver to conduct heat better than about anything else, but getting the heat into the silver might limit the total heat flow so that aluminum would work just as well. That's an oversimplification used for demonstration.

R.

The OP brings up interesting questions, but I have nothing factual to respond with.

What I can say that is semi-related is that I had a well-known cylinder head & intake manifold person who is no longer with us ( ) apply TBCs to my intake & exhaust valves at his suggestion while he was doing some other work for me. After one dyno session where the engine got a post-teardown to check for some other issues, it turned out that some of my new TBC'd Ferrea exhaust valves had actually warped and were no longer seating properly. Well, off came the coatings from ALL the valves, and those exhaust valves that were too distorted to be re-cut w/ new angles were replaced with new valves.

My working hypothesis is that the exhaust coatings applied by that person were not consistent in thickness and resulted in poor heat gradients across the valves' heads, leading to warpage during testing. Future teardowns after that showed no signs of repeat warpage. I still think the idea has merit, but would not use anyone other than a professional coating service to do the application.