The truth behind this...

[95stangGT]

I found this exerpt online, how true is it?

Did you know: Many people don't pay attention to the compression ratio when going from cast iron to aluminum heads. Fact is that if everything else was equal the cast iron head would make more power than an aluminum head. Cast iron heads doesn't absorb heat from the combustion process as fast at aluminum heads, therefore more heat is available to push the piston down. The way to get back the lost horsepower is to up the compression on the aluminum head. Typically you can run about a half to full point more compression with an aluminum head over the cast iron.

 

[95GtTopLess]

Thought biggest difference was weight.

 

[Joes95GT]

All of that is very true. The reason that companies like AFR and Edelbrock make only aluminum heads are because of the weight savings. Most people want an aluminum head because of the performance gains it offers but also because of the weight savings it provides. I don't know why Edelbrock or AFR don't make an iron version of their heads .

Theoretically, you can run more compression and timing with an aluminum head just because it resists detonation better than iron. You can't just mill an aluminum head because "you can run more compression with it". There is much more too it than that. Octane ratings, ignition timing, and cam timing all affect compression.

Joe

 

[StangJonGT]

All of that is very true. Theoretically, you can run more compression and timing with an aluminum head just because it resists detonation better than iron. You can't just mill an aluminum head because "you can run more compression with it". There is much more too it than that. Octane ratings, ignition timing, and cam timing all affect compression.

Joe

x2



Jon

 

[zenboy99]

Thats why most aftermarket aluminum heads have much smaller combustion chambers then stock.

 

[rel3rd]

It's also much easier to "fix" an aluminum head, should it need welding, or whatever...

 

[94CobraPace]

All of that is very true. The reason that companies like AFR and Edelbrock make only aluminum heads are because of the weight savings. Most people want an aluminum head because of the performance gains it offers but also because of the weight savings it provides. I don't know why Edelbrock or AFR don't make an iron version of their heads .
Theoretically, you can run more compression and timing with an aluminum head just because it resists detonation better than iron. You can't just mill an aluminum head because "you can run more compression with it". There is much more too it than that. Octane ratings, ignition timing, and cam timing all affect compression.
Joe

The key word is "everything else was equal". Make a E7 head out of aluminum and the cast iron will make more power. What is the point of making an inferior head like a E7 head out of aluminum. The aftermarket aluminum heads are made to make more power in combustion chamber, port volume, runner design ect because of better design. Weight savings is a bonus.

 

[go-stang5.0]

Also, its worth noting that with all the fancy CNC machines now a days its easier to machine the aluminum heads than iron heads so its faster and therefore more cost effective for the producers.

 

[camaroguy72]

"cast iron" heads are probably cheaper to produce... they are a friggin casting. You do not cast aluminum, it is machined like you said. I would imagine a casting is cheaper... all it really is is forming a mold. I had seen a quad 4 GM head they use a lost foam casting type procedure to make. Think about it... cast heads really have very little machining done to them compared to aluminum heads. Cast is more mass production, not aluminum. thats why there is probably that nice price gap.

 

[tmoss]

You do not cast aluminum, it is machined like you said.

Are you SURE about that????????????

 

[94tang]

aluminum heads are cast too....they just get alot more machine work done to them

 

[camaroguy72]

not sure.. my bad just read it over again. Yea they are "cast" but like 94stang said, lots more machining.... sorry. a regular cast iron head is pretty much left as is... look at the finish of it compared to a aluminum head.

 

[95snoozer]

yes iron makes more power

but the companies would go through way more carbide bits etc etc while CNCing the iron as apposed to the aluminum