Cast iron vs aluminum 302 heads

[Iron Ranger]

Besides weight reduction, what makes the aluminum heads superior to cast iron? I'm not building a high performance street machine, but I just want to know if it's worth spending over a grand vs. just reusing the iron ones I got.

 

[baddad457]

What you really ought to be asking is why are aftermarket 302 heads superior to factory heads. That's the difference. Aftermarket heads just plain make more power. And then sometimes, depending on what all you replace in a stock head in rebuilding them and/or porting them, you end up spending what you would on an aftermarket head. If you don't care about making more power and you have a good set of heads already, then don't sweat aftermarket heads.

 

[rickcdewitt]

you can run almost a point more compression in an aluminum head small block.i don't know how well they will handle over heating though.

 

[red85]

With the aftermarket aluminum heads, the shaping of the ports, combustion chambers and runners often lends itself to smoother flow. After all, why would a company like Trick Flow, AFR or any ony of the others just offer a direct copy of the choked down factory iron units? They usually offer bigger valves too. All these factors just add up to making a motor breathe better. I can and have ported out many sets of E7TE's to flow like crazy, but me spending a couple hours with a die grinder still can't compete with the weight reduction offered with aluminum heads. I could spend as much as a set of decent aluminum heads on having the valve seats enlarged and adding the bigger Chevy valves in a set of GT40's or E7's. In the end it will always boil down to how much do you want to spend to go faster.

 

[baddad457]

you can run almost a point more compression in an aluminum head small block.i don't know how well they will handle over heating though.

You've been reading too many mags. I've run the same compression in iron and aluminum and the tolerance for detonation is the same with the same comp ratio. You are right about their tolerance for overheating, it's less than an iron head.

 

[projectnitemare]

If you will offroad the truck or plan on sitting in traffic for periods of time where overheating could be a concern then you might not want aluminum heads. They will warp much easier than an iron head which will take the heat better.

Matt

 

[Iron Ranger]

As you know, up north here in the great state of Minnesota, where lifts are limited, exhausts are silenced, and emissions are on the "Who Cares" list, very little traffic james, if any (6 cars in front is just about as bad as it gets up here). The truck will be strictly street due to the 2wd, and I aquired the 302 conversion kit which includes the high performance all aluminum radiator, so heat really isn't a problem.

Plus, I thought that aluminum dissipates heat at a much faster rate than cast iron.

 

[85_Ranger4x4]

As you know, up north here in the great state of Minnesota, where lifts are limited, exhausts are silenced, and emissions are on the "Who Cares" list, very little traffic james, if any (6 cars in front is just about as bad as it gets up here). The truck will be strictly street due to the 2wd, and I aquired the 302 conversion kit which includes the high performance all aluminum radiator, so heat really isn't a problem.

Plus, I thought that aluminum dissipates heat at a much faster rate than cast iron.

Aluminum does dissipate heat alot better than iron, but it doesn't take heat as well either.

 

[baddad457]

Don't assume that just because the radiator is aluminum, that it can't overheat. Mine does. And aluminum heads don't run any cooler than iron.

 

[purplehaze]

hey, aluminum heads are weight savn plain and simple, If u just wanna have fun on the street, just go for a set of e7's or gt40 not the p heads either (headache) or redo set of old windsor heads, u can pick these heads up for more than half of set of aluminum heads. aluminum takes heat better than people expect, they cool off faster than steel heads, if u want aluminum u can find them cheap, just look, i just sold my year old set of alum. edelbrock rpm's with crane 1.6 rockers for 900, hope this helps, weight is speed thats what i say, 100lb is a tenth

 

[Will]

I don't know if it's been proven but the aluminum head should be better at avoiding detonation. It WILL give up it's heat more quickly to the coolant than an iron head and it should be cooler in the combustion chamber area than an iron head. Detonation usually occurs when the compressing mixture goes unstable and detonates--it usually occurs at a hot point in the chamber. In theory, the mixture should stay stable at a higher compression in the aluminum head. The problem is testing it. You would have to have two identical engines with variable compression ratios.

In practice, you can do a lot to an iron head to increase it's resistance to detonation. Carefully polish the chamber to get rid of any protrusion. Any protrusion will be a spot that won't do well at getting rid of its heat. It would be a glow plug in there and greately reduce resistance to detonation. I've mirror polished chambers before and run 10-1 compression on pump gas with a carb.

As stated, getting 50# off the front of the car is a great benefit to weight transfer and is less weight to have to accelerate.

And I think even the 5.0 GT heads aren't great above 5,000rpm. If you want to make real power you need some heads with bigger holes through them to move some serious air.

 

[AllanD]

aluminum is far more prone to shrinkage (which is what causes warpage and tension cracks in the chambers)

Gaskets "going away" is a simple fact of life with aluminum heads
(yes, even with studs) because the heads expand more from cold-to-hot
which "squishes" the gasket and elestacity is limited.

Yes, they are lighter, but by enough for the average ranger owner
to feel the difference? Not likely.

Now if you were talking about an aluminum BLOCK for saving weight
(and you could afford the $3500 price tag) I'd say go for it.

a set of GT40 heads from a junkyard explorer (an EARLY 5.0 explorer
to avoid the "P" heads so you can use normal headers) is all you really need.

IF you want more than you can get out of a 5.0 with GT40's
then don't bother going psycho on a 5.0, go with a 5.8

There is no replacement for displacement.

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