head to head

[33 IMP]

for me in a street car I will stick with iron heads.

Kinda also depends on the definition of a street car.
4000 lb street car, the weight savings doesn't mean much. A 3000 lb car, an aluminum head is a no-brainer in my opinion.
Two of my "street cars" have iron heads at the moment, with several sets of aluminum heads on the shelf waiting. The light (mostly strip/street, 2300 lbs) car would never have iron heads in it.

 

[gtxrt]

Kinda also depends on the definition of a street car.

my definition is making a factory car run faster without any negative side effects and keeping the bottom end torque. not running a long duration cam, no single plane intake, too much compression too much gear, too much stall converter and a loud droning exhaust but still gets 16-17 mpg on the highway.

 

[68-500]

Wrong, flat out wrong
it was proven on Engine masters, I suggest you actually check
do some real research, not speculations, or fodder & not spread fallacies like that
that's a wives-tale/false & complete fallacy/internet BS

don't get sucked into that crap

if anything the aluminum heads reduce hot spots, that create detonation
which aides in making power,
& it's more of a difference in a bigger combustion chamber size,
'if any loss of power at all', that even doubtable for the most part
there is so much better technology in alum. casting & cfm flow rates today
even a low compression alum. head combo can make gobbs of power,
with a better port design, than cast iron heads, yeah there are some decent iron heads too
but the material doesn't make it have more power, it the port & combustion chambers
cfm flow that make more power, more than material
(it was never a thing it's wrong, completely & utterly false)
most aluminum heads can be had in a smaller or bigger combustion chamber volume
enhancing compression ratios/or decreasing them...

It has nothing to do with materials, it's about flow
& heat is mostly an enemy to performance, across the board
(cast iron holds heat, hence detonation/dieseling issues)
you don't need more compression with alum. heads,
vs cast iron that an old lie wives-tale/BS
but it will create or dissipate the heat much faster, with alum.

Im not saying your wrong. But there is something to be noted about aluminum thermo conductivity. You will lose some BTU’s out of the combustion chamber with aluminum that might be retained with cast iron and used to push your piston down.
On to the OP question. If the heads were a large limiting factor in volumetric efficiency yes large power increases. If they weren’t a big limiting factor then maybe just a small increase.

 

[gtxrt]

Im not saying your wrong.

you better not Joe Friday and Bill Gannon will be knocking on your door. lol

 

[gtxrt]

Big Joe 2 times engine masters winner on speed talk forums.

 

[PRHeads]

That must have been a really nice set of iron heads. I'm assuming 915s.

Actually, it was two orphaned heads that had the mate to each crack.
I took the best parts from them and matched them up pretty close to each other.
346 heads.

They had been run in a pair of S/G cars by two brothers.
They both ended up making the swap to aluminum heads after they experienced the joy of cracked iron.

 

[33 IMP]

my definition is making a factory car run faster without any negative side effects and keeping the bottom end torque. not running a long duration cam, no single plane intake, too much compression too much gear, too much stall converter and a loud droning exhaust but still gets 16-17 mpg on the highway.

Imo, you described a driver(daily or otherwise) .
MY description of a street car (including mine ) involves a long duration camshaft,(roller) a single plane intake, too much compression, gear and converter. (You forgot giant carburetor). Big exhaust, but no drone however (giant QUIET mufflers, please!)

If it can drive to the track, or the fast food joint, great! If it can't, that's what a trailer is for. I wouldn't think of driving mine from one house (in california) to the other (Az). That's what the 425 hp driver is for (or 700, if you own a hellcat).

 

[33 IMP]

Actually, it was two orphaned heads that had the mate to each crack.
I took the best parts from them and matched them up pretty close to each other.
346 heads.

They had been run in a pair of S/G cars by two brothers.
They both ended up making the swap to aluminum heads after they experienced the joy of cracked iron.

... if for no other reason than easier crack repair.
In my world, every s/g car needs aluminum heads, the lighter the car, the more it needs lightweight heads!

 

[33 IMP]

Big Joe 2 times engine masters winner on speed talk forums.

View attachment 1881502

I think Joe is comparing his ported iron to equivalent flowing aluminum heads. So, he's probably right. But this was years ago, and (almost) nobody does great port work on iron heads anymore (and if they do, they charge an arm and both legs!). Just renewing iron heads with no port work can approach the cost of some aluminum heads, (with LOTS more flow).
Big Joe passed a few years ago, and his son, who races a n/a 10.5 tire Chevy wagon, certainly has aluminum heads on his car.

 

[gtxrt]

MY description of a street car (including mine ) involves a long duration camshaft

that is what i call a race car driven on the street. lol

 

[gtxrt]

engine masters had the heads flowing just about the same iron vs alum but did I miss where they said both heads had the same cc chambers.

 

[33 IMP]

that is what i call a race car driven on the street. lol

Essentially, yep! Lol. (My street strip car....l

 

[33 IMP]

engine masters had the heads flowing just about the same iron vs alum but did I miss where they said both heads had the same cc chambers.

If you are talking about the test I think your talking about (small chevy, identical ports and combustion chamber, aluminum version of an aftermarket iron head, vs the iron head) , it showed basically no difference.
The allure of aluminum is that it's lighter, and probably flows bunches better than 95% of the iron heads out there. (At least the aluminum bbm heads do)

 

[gtxrt]

Essentially, yep! Lol. (My street strip car....l

View attachment 1881675

what is your set up on this car ?

 

[33 IMP]

what is your set up on this car ?

N/A small block, stock brodix heads, flat top trw pistons. A mild solid roller. A glide with a brake and 8" 5300 converter, 9" Ford with a spool and 4.57s. 14x32 slicks for the track, 16x33 dirt tires for the street. At (roughly) 2400 lbs with me in it. I could get to in-n-out fairly quickly.
Not as fast as it should be, but a bright chimpanzee could put the engine together, and since I didn't want it to run nines, I only had to slow it down a bit. (The car would certify for nines, I didn't want to).