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Just what are the advantages of aluminum heads??

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Old 07-23-2000, 11:31 AM   #1
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Just what are the advantages of aluminum heads??

I understand that they are a bit lighter than cast iron heads, but how much extra weight would I be saving on a big block? Are there any other advantages to having them? I am currently trying to figure out what heads I want to run on my 496 stroker. I was looking at the aluminum Brodix BB2x heads, but then I talked to a guy and he said that I may not want to go with aluminum since I am going to be running an 8-71 blower. He said a lot of the guys that run aluminum end up going back to the cast iron because the aluminum flexes and causes problems with adjustments and head gaskets-especially in supercharged applications. Originally, I wanted to get the Brodix BB2x heads because they flow 375 CFM right out of the box. However, the guy I spoke to said that a lot of the guys that go back to using cast iron heads use the Merlin VRs. They only flow 345 CFM out of the box. What sort of cut in power would I be looking at by going with the Merlins and their 30 CFM less airflow and what specifically are the beneifts of aluminum heads? I know they must be lighter, but I can't imagine that it would be such a weight savings that it would make a major difference. Any comments?

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Old 07-23-2000, 12:17 PM   #2
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They are very much lighter than cast iron heads but the biggest advantage is head disipation. As an example if an engine can go up to 10:1 compression before it starts pinging with cast iron heads then aluminim heads can go to 11:1. Being able to disipate head better will allow an engine to build more power.

Bigger flow numbers don't always mean more power. Head flow is like carbs, headers, torque converters and gears. Bigger isn't always better.

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Old 07-23-2000, 01:09 PM   #3
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My cousin runs STOCK performer rpms aluminums on his 350 with a 6-71 (10-12lbs of boost).

It runs 9.80s with 0 problems..

In 3 years of racing on this motor he's had to change the head gasket once..

You'll probably save at least 80lbs off the front of your motor with those aluminum heads. Plus with a blower you will be able to run more timing without detonation.

I would think with a blower you would definitely want alumnimum!

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Old 07-23-2000, 03:26 PM   #4
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and if you break one they're easy to weld and remachine.
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Old 07-24-2000, 12:07 AM   #5
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One correction: one of the drawbacks to aluminum(vs cast-iron) cylinder heads is their heat dissipation properties. Aluminum does not retain heat very well, and heat is what you need to keep in the combustion area to make power. One way around this is to coat the combustion chamber and the tops of the pistons(which are also made of aluminum) with a ceramic coating. This does not actually improve the heat retention of the aluminum, but reflects the heat back into the combustion area. This prevents the aluminum from absorbing the heat and dissipating it outside the combustion area. It also prevents the aluminum cylinder head from conducting heat into the intake ports, allowing the ports to deliver a cooler, denser charge into the combustion area. Further, if the exhaust ports are similiarly coated, retained heat in the exhaust port will help maintain the velocity of the gases being evacuated.

Because aluminum does a poor job of retaining heat in the combustion area, an engine with an aluminum cylinder head requires a higher compression ratio, than an identical engine with a cast-iron cylinder head, to make the same power as the engine with the iron head.

Another area of concern, as far as concerns aluminum cylinder heads, is cold weather operation. Because the aluminum cylinder head, the cast-iron block and the steel bolts joining them, all undergo heat expansion at different rates: as they heat, stresses occur at the mating points. The aluminum is the softest of these three metals, and it is the most likely to fatigue from these stresses.

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Old 07-24-2000, 10:03 AM   #6
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88 Iroc is dead on right!

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