Yelo

What are the major differences between the two (I mean other than one is steel and the other is aluminum)...as far as I have been able to find out they are the same casting design, have the same size runners, use the same size valves, and make roughly the same power.....I have even gone as far as researching flow data and the 6.0 aluminum, 6.0 steel, and Z06 heads all flow within 2-3% of one another....

So...other than material, and the ability of the aluminum heads to dissapate heat better is there any real difference ??

The reason I ask is because I have 6.0 steel heads and if I can avoid swapping them in the future to make more power I would like to (a head swap on a daily driver is kind of a bitch)

Slowverado

the iron heads are junk....they are heavy, they are hard to port and machine. they are good boat ancors though.

Yelo

but if you own already own them, don't care what they weigh (5700 lb truck...like another 100 lbs matters..), don't plan to port or machine them, and don't have a boat to anchor they still flow the same as the aluminum heads...right ??

Hit Man X

Well don't knock iron heads. Many people use them and make good power...

I had a 302 SBF with GT-40 iron heads, E303 cam, Cobra intake, and all other bolt ones and made 230rwhp/260rwtq through a fully built AOD trans, PI Stallion converter, very long 4 door car driveshaft, and 4.10:1 gears...I assume I lost around 40-50rwhp due to my driveline setup.

I made 320rwhp/390rwtq on the spray with the same combo. That would put me around 270rwhp/300rwtq on motor and 360rwhp/430rwtq with the losses...not too bad for a 302 with iron heads.

Ran mid 8 sec in the 1/8th mi on the spray and low 9's on the motor in a 4400lbs car...with a rich pig shitty tune and low timing.

I have seen those box stock heads make close to 290rwhp with all boltons through T5 and 3.55:1s

If you don't know a fully built trans will sap a bitmore power as there is more crap inside to turn on top of the 22-25% loss, those PI converters lose a lot of power through them being small diameter as well as loose, low gears lose power (check in the drivetrain section of this site), and that long *** driveshaft doesn't help either.

The way I see it...run with what ya got! It is cheaper.

Tom@SpeedInc

iTrader: (5)

I don't think you would find much advantages to switching to alloy heads without intention re engineering the engine with high compression, stroke. Obviously you have found your truck to not be a boat anchor so why bother. A steel head will last decades longer then a alloy head, does caterpillar use alloy blocks/heads no! my dad is an engineer at EMD of GM and they like to pride themself on having a steel engine for most durability. Plus their a whole bunch of theroy of alloy head steel block engines having a issue with heat expansion. Of course alloy is good for high compression cause it lowers the cylinder temp, compression is heat. The switch from steel to alloy heads on 6.0 I don't belive was to raise engine performance, GM like every other manufacture is gloabalised and it is cheaper if all their truck engines share the most parts. Building unique cool sh*T that could benifit their whole product lines image just doesn't cut in the board room, making money is what it is all about.
But alloy is lighter, and with a cooler combustion chamber will lower NOx (nitric oxide) levels, NOx isn't mandated by IM240 testing only to a new vehicle manufacture I think.
Like the diff between LQ4 and LQ9 engines I think are only the pistons...........

FarmTruc

iTrader: (5)

there's no difference between the iron heads and aluminum heads as far as making power, there is no proven test that shows the aluminum ones make more power. The only advantage is they are lighter,
Porting: that's why there are bits for iron and that's why there are bits for aluminum. if your trying to port iron heads with a soft bit i could see how they are harder to port, lol

keep your iron heads , the trouble of going to aluminum heads isn't worth it.

BADMOFO

Bill "Grumpy" Jenkins once told me, "Iron heads make and hold heat...and heat makes Power!" Who ever said they are only good for boat anchors obviously doesn't understand the principles of the internal combustion engine. Go argue with the Grump, and tell him he's wrong.

CashDudeHomie

iTrader: (5)

So if I install a 250 degree thermostat, I will make more power?

Slowverado

badmofo...the grump was running highly bad *** motors that ran for what, 7-10 seconds at a time? as far as building heat to make horsepower, yes it does make power, but no it will not make any more power than an LS1 or otherwise aluminum head. the grump was talking about drag racing applications NOT street driving. talk to any racer today, anyone making really badass horsepower is using aluminum heads. top fuel cars don't run iron heads and they are the most powerful INTERNAL COMBUSTION motors in the world. and yes i would argue with the grump on this....of course i'd argue with a wall but still.
and yes i do understand the principles of an internal combustion engine.

cashdude...lmao.

Tom@SpeedInc

iTrader: (5)

Pro Mods and top fuel cars run alloy blocks and heads for weight savings but also aluminum blocks and heads are 100% repairable. You can window a TFX block and weld it back together, far as real world benifit you can repair cracks in alloy heads and fix a warped head by baking it. With iron you can fix some cracks but for the most part its junk. Grumpy saying heat is power yeah, heat is compression so long as you have fuels that have enough anti knock you coudl take advantage of that. For running higher compression on pump gas you need alloy heads.