iron vs aluminum heads

grumpyvette

Administrator
Staff member
The most important factors in my opinion are the weight savings and the ease of repair and doing port work,aluminum cools, the combustion chambers better, and transfers heat to the coolant and oil,faster, due to its increased thermal conductivity,
lowering your tendency to get into detonation with crappy, low octane fuel, as well as its lower weight but the main advantage in my opinion is its far easier and cheaper to repair, you generally throw cracked steel heads in a dumpster while you tig weld and re-machine aluminum heads WHEN THEY GET DAMAGED and they are like new
keep in mind most aluminum heads will frequently require longer head bolts or studs and washers being used under the bolt heads or stud nuts to prevent the nuts or bolt heads from wearing or damaging the soft aluminum at the contact pressure point, failure to use the hardened washers frequently results in torque readings that are not consistent and eventual damage to the heads

the material the heads are manufactured from will have a big effect on their ability to dissipate the heat quickly from the combustion chamber, increasing compression tends to increase the heat generated during combustion, aluminum transfers heat much faster than iron into the coolant, and its that factor more than most that forces you to reduce the effective compression slightly compared to an aluminum head IF your getting into the detonation range due to heat, of combustion, compression,and the ignition advance
the surface Finnish and shape of the combustion chamber and piston dome,coolant temp. air temp,the combustion chambers tumble and swirl, the fuel octane, the quench/squish distance, spark plug heat range, also will effect your engines tendency to reach detonation
as a general rule on pump gas the temp in the combustion chamber is the limiting factor on reaching detonation.

http://www.chevytalk.org/fusionbb/showtopic.php?tid/92966/
0311phr_compress_07_z.jpg


http://www.competitionproducts.com/...c-Bare-Pair/productinfo/PMX9317/#.V2m23PkrLcc
short answer, aluminum tends to allow you to run about 1/4-to-1/2 point more effective compression, IE, if iron heads get into detonation at 10:1 ALUMINUM might ALLOW YOU TO RUN 10.3-10.4:1 BEFORE GETTING INTO DETONATION, BUT ON THE PLUS SIDE AT LEAST IN THEORY IRON HEADS AT ANY GIVEN CPR WILL HAVE A SLIGHT ADVANTAGE IN HP
but in my real world testing the difference is much closer almost non-existent
the main advantage I see in aluminum heads is lighter weight and their much easier to repair when damaged
an aluminum cylinder head allows heat transfer to the engine coolant at a significantly higher rate than an iron head, and generally about .25-.50 higher compression can be tolerated but theres No absolute real definite answer, depends on quench, cam LSA, cylinder head design, advance curve, fuel/air mixture, intake temperature, coolant temp, spark plug design, piston design, heat barrier coatings, combustion chamber surface texture, and a bunch of other parameters.



http://www.carcraft.com/techarticles/cc ... sults.html

http://www.bpeheads.com/sonnyleonard.htm

http://www.kennedysdynotune.com/Dynamic Compression Tech.htm

http://www.misterfixit.com/deton.htm

http://www.kb-silvolite.com/article.php ... ad&A_id=36

http://www.geocities.com/vpracegasatlan ... tfuels.doc

http://www.chevymania.com/tech/vortec.htm

viewtopic.php?f=50&t=10728

http://www.j-performance.com/index.php? ... view&id=48

http://www.profilerperformance.com/sbc-heads-176.html

 
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grumpyvette

Administrator
Staff member
increasing combustion chamber heat can potentially boost cylinder pressures and torque, it can also increase the engines tendency to get into detonation if that increased heats not carefully controlled.the weight savings and reduced tendency to reach detonation temps on aluminum heads are a big help but being able to far more cheaply and easily weld and repair mechanical and structural failures like cracks is a HUGE HELP, a cracked set of iron heads is usually a good door stop, but aluminum is easy to repair
aluminum heads are FAR easier and less expensive to repair when damaged, thats a HUGE advantage!
aluminum tends to transfer heat to the coolant far more efficiently than iron will and as a result un -coated aluminum tends to reduce combustion chamber temperatures slightly, aluminum also weights less, so in many cases aluminum heads will tend to make the car slightly less prone to detonation and lighter in weight.
naturally there are heat barrier coatings that can be added to pistons and combustion chambers to allow you to retain much of the heat if your just looking to reduce weight.
acceleration, is effected by the cars weight reducing weight tends to make the car faster.
one other factor to think about is that many aluminum heads have newer and more advanced combustion chamber and port designs, making them flow better.

well worth reading
http://www.hotrod.com/techarticles/alum ... index.html

http://www.hotrod.com/howto/3448_alumin ... index.html

http://www.chevyhiperformance.com/techa ... index.html

http://www.carcraft.com/techarticles/cc ... t/index.ht


http://www.hotrod.com/techarticles/alum ... index.html

viewtopic.php?f=53&t=2610&p=6737&hilit=coating#p6737

viewtopic.php?f=52&t=2630&p=6788&hilit=shrouding#p6788

viewtopic.php?f=52&t=796

viewtopic.php?f=52&t=181
 

grumpyvette

Administrator
Staff member
http://www.youtube.com/watch?v=JBkgJNES ... re=related

viewtopic.php?f=52&t=3956&p=10561&hilit=+aluminum+weld+heads+iron#p10561

watch this video, its a good reason to buy and use aluminum heads like BRODIX sells

http://garage.grumpysperformance.com/index.php?threads/aluminum-head-tig-repairs.3956/#post-10561

http://garage.grumpysperformance.com/index.php?threads/aluminum-heads-polishing-and-porosity.14689/

http://garage.grumpysperformance.co...ing-cast-iron-can-make-a-preacher-cuss.12647/

aluminum heads can be easily welded to make repairs if damaged
but one factor on a bbc engine is weight, a iron head weights close to 74 lbs , aluminum heads tend to be 20 plus lb lighter in weight each, so saving 40 lbs -50 lbs off the front of the car plus anouther 5 for an aluminum water pump and another 20lbs with an aluminum intake makes a great deal of difference in total engine weight
bbcheadwa.jpg

bbcheadwb.jpg

http://indyheads.com/images/price2012.34.pdf



heres the real main reason aluminum's preferred, when you screw up you can weld aluminum and get it re-machined back to as new condition , even when heads get trashed like this
obviously you need to ask what youll be using the heads on (displacement and intended use) but Ive had good results with these DART iron heads if you are restricted to using iron heads,

http://www.dartheads.com/products/cylin ... heads.html
or
http://www.jegs.com/i/GM+Performance/80 ... 6/10002/-1

the reason most people use iron heads are either rules limiting the use of aluminum and weight savings or cost issues, but the more expensive true performance iron heads, the cost quickly becomes a non-issue for several reasons, and iron heads cost more to have ported, and are much harder to repair if damaged

do the same damage to iron heads and they only make decent door stops
Aluminum does have advantages, like light weight, and easy of machining compared to cast iron, example,cracks in valve seats on iron heads ",usually the result of overheating,"tend to result in coolant leaks that are not easily repaired, so you need a new cylinder head even if you had hundreds of dollars in port work done previously.
but on aluminum heads a bit of tig welding and machining for new valve seats repairs the heads rather easily
fe900x.jpg


but because they were aluminum ,both heads below are easily repaired

headpics003.jpg

head02.jpg

obviously the people you deal with and the extent of damage will vary wildly but Ive had damage similar to the picture above on a cylinder head , had a valve punch a quarter size hole in a combustion chamber roof and busted a valve guide and the repair cost me $300 which I thought was reasonable, and it looked new when it was returned

READ THIS INFO


http://www.carcraft.com/techarticles/cc ... ewall.html

viewtopic.php?f=51&t=3363&p=8863#p8863
 
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grumpyvette

Administrator
Staff member
hey grumpyvette?
I am thinking of going to a Aluminum head set up for my 1959. impala, I have a 383 short block. However, there is allot of choice and opinions out there. This is what I was looking at, so let me list what I have.
350 block. .030 over.
Eagle steel cast crank 400.
5.75 rods.
KB Hypereutic Pistons #197 12cc dish
ZZ4 roller camshaft 208/221 duration @.05 474/510 lift with 1.5, 112sep.
Bottom end was pro built, balanced.

Heads I am looking at.
Aluminum 64 cc chambers
210 Intake port
2.02/1.6 Stainless valves
.650 Dual lift springs
Screw in Studs
No steam Holes (help here)

I am hoping to keep the CR at 10 - 1.
3.36 rear. Not sure on trans..probably TH350. Performer Intake.
How is this set up looking for me? The heads are brand new. Not sure how to figure the CR.
Thanks in Advance.


ok lets take a minute to point out a few factors here that are OBVIOUSLY NOT BEING ADDRESSED.
port cross sectional area effects air flow speed in the port, the displacement and cam timing will also effect the air flow speed in the intake ports, the air flow speed effects the cylinders ability and efficiency to fill and those factors will have a pronounce effect on the engines torque curve, its likely to produce.

viewtopic.php?f=52&t=322

viewtopic.php?f=52&t=1070

viewtopic.php?f=52&t=4221

http://www.superchevy.com/technical/eng ... index.html

viewtopic.php?f=52&t=333

viewtopic.php?f=52&t=1070

viewtopic.php?f=55&t=858&p=3801&hilit=SECTIONAL#p3801

viewtopic.php?f=71&t=741

http://garage.grumpysperformance.com/index.php?threads/aluminum-heads-polishing-and-porosity.14689/

short version,WHEN BUILDING on a 350-383 displacement , SBC COMBO, a 210cc sbc CYLINDER HEADS ports designed for max efficiency in about the 5000-7000rpm band, a 208-210 intake duration cams designed for max efficiency in the 2000-4500rpm power band
Duration_v_RPM-Range_wIntakeManifold01.jpg

fe008cfd.gif


as is a performer INTAKE, and a 3.36:1 rear gear ratio,you'll be far better off using a vortec style intake port size in the 170-180cc range if your using that rear gear and cam OR if you want to maximize the 210cc port size, a PERFORMER RPM INTAKE, a 3000 rpm stall converter,a cam with about a 245-250 intake duration and a 3.73-4.11:1 rear gear will sure help

read these links also


viewtopic.php?f=52&t=3956&p=10561&hilit=iron+vs+aluminum#p10561

viewtopic.php?f=52&t=2765&p=7180&hilit=iron+vs+aluminum#p7180

viewtopic.php?f=52&t=462&p=22497&hilit=porting+help#p22497

viewtopic.php?f=52&t=4715&p=12810&hilit=chamber+shroud#p12810

viewtopic.php?f=50&t=4618&p=13240#p13240




viewtopic.php?f=52&t=534
 
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grumpyvette

Administrator
Staff member
heres an example of why ALUMINUM HEADS ARE MUCH MORE REPAIRABLE AND WHY YOU SHOULD DEAL WITH AN EXPERIENCED CYLINDER HEAD REPAIR AND PORTING SHOP
aluminum's far easier to TIG WELD
below is a badly damaged BIG BLOCK CHEVY head, off a super charged engine that had a blown head gasket and the resulting extensive flame cutting caused extensive damage
almr1.jpg

some rather extensive grinding to get to clean metal
almr4.jpg

some extensive tig welding
almr3.jpg

some machine work to get it back to original specs and its going to be 100% functional again

almr2.jpg



alblock.jpg


ouch! that block above, hurt some guys bank balance HARD!
unlike cast iron aluminum can be re-welded and re-machined but that looks financially to be a lost cause.
 
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Indycars

Administrator
Staff member

Welding two pieces together is one thing, but building up a wall
between the water jacket and the outside is totally different.
Much harder I would expect!

 

Altered76

Member
I didnt read all the links but I can say I agree with most if not all of this. I have noticed a trend over the years about aluminum heads.

Back in the 80s Aluminum heads had to overcome a reputation of being weak and problematic. Much of this was misinformation or assumption due to production heads being abused and treated like shit by the general public. Normal car maintenance is not one of the most properly followed tasks for non-car gurus. :oops:

The aftermarket started coming on after that mass producing heads but they were quite pricey and generally generic designs for race only applications. As any one knows if you mathematically cannot afford it it makes no difference how damn good it is. The general street enthusiast or hometown bracket racer just was not budgeted for the initial cost of these. As time has passed the used market has become filled and prices have come to be more reasonable for the average car guy.

The evolution of aluminum heads has come into its rightful place. Heads have become plentiful, much more reasonably priced, many variations to suite particular engine combinations, along with the old favorites become more and more scarce. Common knowledge is name brands such as Brodix Dart AFR etc all produce quality heads that when matched properly produce superior results to any factory head.

A few things I feel that make Aluminum heads the best choice:
Cost
Repairable
Porting Easier less expensive if even necessary
CNC Machined Accuracy repeat ability


The 40 yr + generation has been around to see the transformation of these easy bolt on goodness. :)
 
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