aluminum HC heads vs Cast iron HC heads

[FrankWest107]

You hear a lot about aluminum HC heads to improve HP output.

What is the real advantage of an Aluminum head?

[K8096]

What kind of car are you talking about?   A pre war flathead, or a 1960's-70's muscle car?   

[FrankWest107]

1933 ford 4 cylinder

[Paul Dobbin]

Frank,

i was unaware of the 4 cylinder 33 Ford with aluminum a head.  But, I'm a 34 Ford V8 guy.  For some reason I thought C heads were cast iron when I've heard of them used on Model A's.

I've used both and prefer the cast iron heads, with aluminum paint.  The 82 year old aluminum heads have a tendency to have the water jacket hole grow until they allow water into the compression chamber and to stick to the head studs,,  the cast one don't.

Plus the cast heads are a lot easier to take off after they've be on awhile.  I never saw anybody put magnet to the heads, so the aluminum paint makes them look correct.

[K8096]

I've been told cars run a little cooler with aluminum heads as the aluminum dissipates heat better than cast iron.   

[jrbartlett]

Agree with K8096 on the heat dissipation advantage of aluminum -- I've read that a number of times. However this also conveys another advantage. It allows somewhat higher compression without posing as much risk of pre-detonation, due to the fact that the aluminum head is disposing of heat better and preventing creation of hot spots that could serve as ignition sources. Of course the head would have to be designed with this in mind regarding the volume of the combustion chamber, a factor in determining compression ratio.  

[Guest aust1934ford]

      Yes, I also agree with K8096 & jrbartlett,

I believe the reason for using the aluminum heads was to help the engine run cooler. The 1933-34 ford V8 used the aluminum heads on

passenger cars but the cast irons' were used on the commercials.

However due to corrosive issues the al. heads can be a 'pain' to remove

after many? yrs.     

[Spinneyhill]

Sorry gentlemen, I think it is unlikely an aluminium head will aid engine cooling. Yes, the thermal conductivity of aluminium is about 2.5 to 5 times that of gray cast iron. But the limiting factor is the thermal conductivity and temperature of the air passing over it. They cannot unload heat any faster than the air can take it in.

 

Aluminium is significantly less dense than iron, hence a lighter car -> better fuel economy and better performance.

Edited May 4, 2016 by Spinneyhill (see edit history)

[Guest aust1934ford]

Hello, Correct me if I am wrong,

But doesn't the water/coolant passing through the aluminum heads play a significant part in keeping the top combustion area cooler,

as well as you mentioned air passing over it.

  

 

[8E45E]

Hence the reason for the multiple cooling fins on them.

 

Craig

[Spinneyhill]

22 hours ago, aust1934ford said:

Hello, Correct me if I am wrong,

But doesn't the water/coolant passing through the aluminum heads play a significant part in keeping the top combustion area cooler,

as well as you mentioned air passing over it.

 

 

Of course. How silly of me. The cooling is governed by the heat capacity of the coolants, water (usually) and air. Yes, cooling fins will help by increasing the surface area in contact with the air.