Originally Posted by madscientist
Originally Posted by HotRodDave
Originally Posted by tubtar
No love for thermal barrier coatings ?
With high compression and low octane , combustion chamber heat can be reduced by coating the piston and chamber.
I have read some interesting results from this.


I am still undecided about coatings, here is why.

We know running aluminum heads can allow you around another full point of compression vs an otherwise identical iron head, the reason is it conducts the heat away from any hot spot faster so the hottest point in the chamber is no longer as hot and no longer as likely to pre-ignite the fuel. Same with the piston, the heat can spread out faster from any given point. Now we would add a ceramic coating that does the exact opposite...? It is possible I am missing something, maybe just keeping the heat from being absorbed in the first place outweighs it but my though is that it would just have a hot spot with the piston behind it still trying to transfer heat evenly through out but the surface could more easily develop a hot spot, sort of an in between of the properties of aluminum and iron...

One other thing I like to do that seems to work really well for me is running as flat a piston as possible, for example a 318 with stock flat top pistons, no valve reliefs set with a real tight quench and magnum heads let me get away with very high compression, lowest surface area possible for a piston to keep it from absorbing heat... it may be worthwhile to run a head with a bigger chamber so you can run less or no dish in the piston. I always prefer a perfectly flat piston if possible.



There is ZERO truth to the oft repeated nonsense that aluminum heads can use a point more compression than iron. None. Guys running iron heads can run the same compression as guys running aluminum heads. It’s ridiculous to keep saying that falsehood. There is no possible way in hell that running along at a cruise and running into tip in rattle will stop if you switch to aluminum. Common sense says the increase in heat load happens so fast it wouldn’t matter if the heads were made of unobtainimum it wouldn’t matter.

There are no “tricks” to running more compression than the “orthodox” standards we have been lead to believe. Common sense engine building, cam selection and chassis isnt trickeration. It’s common sense.



Aluminum helps reduce detonation not just because of what happens over the course of one particular engine cycle, it helps because over the last several thousand cycles previous to that one particular cycle the heat has spread out more evenly throughout the cylinder head instead of staying more in one spot like it would have if the heads were iron. You can experience the same phenomenon when heating a head to remove a broken exhaust bolt, you put the heat on a broken bolt in an iron head and it will very quickly heat up the area the bolt is in and the rest of the head temp barely changes temps if at all and that spot will stay hotter much longer than if you do the same thing on an aluminum head, that hot spot around the broken bolt cools off waaaaay faster and the heat is much more quickly spread out through out the rest of the head. The aluminum spreads out the heat over time and prevents hot spots much more effectively than iron. You are ignoring the heat dissipation over time and focusing on one small slice of time where both heads are perfectly exact temp through out but over running time that is far from what is happening inside the engine.

I am not causing global warming, I am just trying to hold off a impending Ice Age!