I always thought aluminum heads absorb/remove heat from combustion chambers taxing the cooling system and allowing more compression? Luckily I can read the experts on here to educate and set me straight. As you were carry on with the bickering back and forth pictures of Vegas and stock 340s that could out run Hemis ect ect ect....
This has been discussed to DEATH but it still comes up. Here is the TRUTH about this crap.
When you are rolling down the road and you step down on the throttle and it rattles a bit you have what’s called “tip in“ detonation.
So, the rate of change of heat happens so fast that the aluminum can’t possible transfer the heat to the coolant fast enough. It just can’t. That rate of change is so fast the heat can’t get dumped into the coolant fast enough to reduce or control detonation.
The exact same thing occurs when you mash on it hard and get into rattle. The heat rise is so fast that there is no way the heat can get through the head, into the coolant and then control the heat to control detonation.
Now, if you want to watch the Engine Masters episode where they tested this they found no HP difference (they found 2 or 3 HP with one of the heads…I don’t remember if the aluminum head made more power or if the cast iron head made more power but at 2 or 3 HP…thats clearly in the margin of error as 10 degrees of oil temperature can cause that HP gain/loss) you will see what they do to say the aluminum head can dissipate heat better.
They laid on the engine to the point they heat saturated the engine and at that showed that the aluminum head got rid of heat quicker than cast iron.
And I called BULLSHIT on that as soon as I watched it. No one with the IQ of a potted plant would ever, in good conscience would do that to an engine.
That is the equivalent of pulling a 6% grade for 5 miles and NEVER downshifting. Who does that? No one.
Ao that part of the test is about worthless, unless you drive like an idiot.
Go watch the EM episode and see what they had to do to make the aluminum head LOOK like it can take more compression than an iron head. See if you would drive an engine like that.
I know I don’t.
