Cast Iron vs Aluminum Cylinder Heads [Archive] - Chevelle Tech

: Cast Iron vs Aluminum Cylinder Heads


Dave427
Jan 12th, 11, 5:16 PM
I have my 427 SB out of my car due to a leaky head gasket or cracked head who knows yet?
I know a cast iron head if everything is equal makes a bit more power than an aluminum head.
But an aluminum head is more repairable over a cast iron if something breaks or detontation etc.
But whats more reliable for leaks?

Opinions Dave

big_orange
Jan 12th, 11, 5:20 PM
a good head gasket;)

Dave427
Jan 12th, 11, 5:34 PM
a good head gasket;)
True , I thought I had one :(

I have a Motown Block with a 4.125 bore (no steam holes)
Fel Pro 1003 ?

Dave

GRN69CHV
Jan 12th, 11, 7:13 PM
Dave, just had the Dart heads freshened up. Deck surfaces were cut to just about a mirror, block is at the machine shop getting finished, I did see it after it was decked, same deal. Plan to use MLS head gaskets. Another worthwhile investment (in my opinion) is a head stud kit. I'd stay with your plan of just fixing what you have and make needed improvements along the way.

mrpaticular
Jan 12th, 11, 7:42 PM
I have always used Permatex Hi Tack spray. Been using it since 1970 with up to 11:5 compression and steel shim gaskets. Like the others said, quality machine work. I did drop a valve once and scraped out a very nice 049.

karl
Jan 12th, 11, 9:10 PM
I prefer alum because it is lighter and i can get away with higher compression on the same gas. And in alot of cases easier to repair. Im sure iron has some advantage (like price) but not enough for me.

PRO 48 Fleetline
Jan 12th, 11, 9:37 PM
I personally like an aluminum head i had to wait a lil longer to get the set i wanted but really worth it i bought a set of 210 Pro-filers from Chad speiers love um i threw them on the scale before i buttoned up the block and the steel head weighted 48 lbs. the aluminum 25 lbs. basicly two heads the weight of a steel one, around 50 lbs is alot of weight to save aswell.

Dave427
Jan 12th, 11, 11:48 PM
Well I will find out what happened to this thing and decide from there.
If they aren't damaged its the smart way to go and re-use them. then add my new solid roller.

Dave

Wolfplace
Jan 13th, 11, 1:07 AM
Well I will find out what happened to this thing and decide from there.
If they aren't damaged its the smart way to go and re-use them. then add my new solid roller.

Dave

Good plan :thumbsup:
As far as a power difference in theory the cast head might make more but this just hasn't been shown to be true in the real world
It has been tested by one of the magazines a few years ago & it was a pretty decent test as I recall with "like heads"
The Aluminum ones actually made slightly more power

I do have one test we did a while back
It was the Dart iron Platinum vs the Dart aluminum which are supposed to be the same or very close to it
We took a set of Platinum 215cc Iron heads off a circle track deal & stuck the Dart 215cc aluminum heads on with no other changes
The power was too close to call & this is without bumping the compression which means the aluminum head probably would have been the winner if things went as they are "supposed" to
If memory serves the torque was slightly better with the iron head but the peak power was higher with the aluminum but again it was within testing error for me

BillyGman
Jan 13th, 11, 1:14 AM
I know a cast iron head if everything is equal makes a bit more power than an aluminum head.
Not that I am aware of. :noway: But besides that, if you choose aftermarket aluminum heads, you have a plethora of options available to you, and with those options comes more power. I believe that there are a number of aftermarket aluminum heads that flow better and make more power right out of the box than some ported iron heads do.

Scotch
Jan 13th, 11, 10:30 AM
The theory was that iron heads would hold more heat in the chamber, while the aluminum heads would shed that heat into the cooling system more readily than the iron.

That all makes sense, but all the new chamber research shows up in aluminum heads first nowadays, so a more efficient chamber in an aluminum head more than makes up for any potential heat loss over an iron head with a lesser chamber design.

Personally, I'm a huge fan of internal engine coatings. I get the best aluminum heads I can, and then coat the chambers, valves, ports, and piston tops with ceramic engine coatings. This insulates the chambers/ports and keeps more of the heat in the chamber.

Because of the coatings and the weight savings, not to mention the ease of repairs, I'll never run an iron head again. It's like the roller cam thing- yes, they're more expensive, but I'll never run a flat tappet again either. Too many advantages to rollers...and aluminum heads, for that matter.

atle
Jan 13th, 11, 11:27 AM
Personally, I'm a huge fan of internal engine coatings. I get the best aluminum heads I can, and then coat the chambers, valves, ports, and piston tops with ceramic engine coatings. This insulates the chambers/ports and keeps more of the heat in the chamber.


Hey Scott, could you elaborate on the ceramic coating? Is this something a backyard wrencher can do? Or do you need to bring it to a machine shop? Thanks.

BillyGman
Jan 13th, 11, 1:24 PM
Some companies such as Tech Line sell coatings for the do-it-yourselfers, although I don't know if that would work as well as coatings that you can get professionally applied. Anyways the internal engine coatings are supposed to keep engine parts cooler and "reflect" the heat. Kind of like ceramic coatings on exhaust headers.

atle
Jan 13th, 11, 1:38 PM
thanks Billy

Dave427
Jan 13th, 11, 1:50 PM
Ok answer this is an aluminum head prone to a leaky head gasket over iron?

Dave

BillyGman
Jan 13th, 11, 2:21 PM
Ok answer this is an aluminum head prone to a leaky head gasket over iron?

DaveAluminum heads might warp easier IF, the engine is overheated, but factory aluminum heads are more known for warping than most aftermarket aluminum heads are. Airflow Research ("AFR") aluminum heads have .750" thick decks so they resist warpage, and many other companies have decks on their heads that are almost as thick (Brodix, Edelbrock, etc., etc) which are considerably thicker than factory aluminum head decks are as far as I know.

The only time I've ever had head gasket leaks with aluminum heads is when I used those paper thin .015" thick steel shimmed gaskets. And it stated right on the gasket package (Fel Pro) that the surface finish of both the block and the cylinder head decks needed to be a certain smoothness (I believe it's measured with an "RA" number) and it was a factory iron block I was using, which did not have a smooth enough finish. Someone in an automotive machine shop told me at the time that factory heads and blocks have deck surfaces that are milled, but that the surfaces needed to be ground to be smooth enough for the thin steel shimmed head gaskets.

I had checked both the head and block surfaces for warpage, and they were NOT warped. When I had switched to the standard .039" thick Perma-Torque fel Pro composite head gaskets, the problem was solved, and I never had any coolant leaks like I was having with the .015" thick steel shimmed head gaskets (and YES, I used the copper spray on the steel shimmed gaskets during installation, but that didn't prevent the coolant from leaking into the oil). But I digress...

As far as I know, aluminum heads aren't any different than iron heads as far as the chances of head gasket leaks go. You might want to place a straight edge tool diagonally, horizontally, and vetically across the surfaces of both the engine block cylinder banks and the cylinder head decks, and attempt to slip a .005" feeler gage between the deck surfaces and the straight edge tool to check for possible warpage. If you cannot get the feeler gage in, then that should rule out warpage.

Scotch
Jan 13th, 11, 5:27 PM
Hey Scott, could you elaborate on the ceramic coating? Is this something a backyard wrencher can do? Or do you need to bring it to a machine shop? Thanks.

Technically, you could do it yourself. The parts need to be super-clean (blast cabinet + good wipedown) and they need to spend some time in an oven. The coatings are applied with an airbrush, so you need to have one of those and a suitable compressor. No biggie..

But, if the coatings aren't applied correctly, they won't stick. So I take my stuff to people who do it everyday.

I had one set of heads done by Calico Coatings (www.calicocoatings.com) and they did a great job. I recently had another set done at TPI Specialties (www.tpis.com) since they're local to me. Also a great result.

The company that makes the coating I use is called Tech Line Coatings. Great stuff.

GOSFAST
Jan 13th, 11, 7:35 PM
I've placed a link below to the "Speedtalk" site with some interesting input from some of the most respected and knowledgable engine guy's in the country!

It explains the cast iron vs. aluminum combo's in some detail!

(Add) Actually it was the guy's at "Dart" some years back that passed along the "iron heads make the most power" scenario to us. We had known it earlier from our own testing, but they confirmed it for us!

Thanks, Gary in N.Y.

P.S. Here's the link to some valuable info! If you do an add'l search over there (cast iron vs aluminum) you will find much more input!

http://speedtalk.com/forum/viewtopic.php?f=1&t=2146&start=0&sid=ad33786137cd325e4ef5772396a738e0

Wolfplace
Jan 18th, 11, 1:51 AM
I've placed a link below to the "Speedtalk" site with some interesting input from some of the most respected and knowledgable engine guy's in the country!

It explains the cast iron vs. aluminum combo's in some detail!

(Add) Actually it was the guy's at "Dart" some years back that passed along the "iron heads make the most power" scenario to us. We had known it earlier from our own testing, but they confirmed it for us!

Thanks, Gary in N.Y.

P.S. Here's the link to some valuable info! If you do an add'l search over there (cast iron vs aluminum) you will find much more input!

http://speedtalk.com/forum/viewtopic.php?f=1&t=2146&start=0&sid=ad33786137cd325e4ef5772396a738e0

That Speedtalk thread had some great info, I remember it because I had just changed blocks in a pretty serious SB deal when that thread evolved & was glad to see the same trends as others I respect did

But the questions here are about aluminum heads not blocks & the differences are much smaller.
In the test I posted earlier that was about as comparable as one could get being as most changes are to a "better head" or some other change so the testing gets skewed it followed the test done by one of the rags a while back

Thanks for the link, I really enjoyed reading it again

Two Lane
Jan 18th, 11, 1:20 PM
But the questions here

are about aluminum heads

not blocks




Thank you for getting the thread back on the rails! ;)

Two Lane
Jan 18th, 11, 1:33 PM
Anyways the internal engine coatings

are supposed to keep engine parts

cooler and "reflect" the heat.




Little bit more to them than just that. :)


Get your info on @: http://www.calicocoatings.com/faqs/


HTH :)

Wolfplace
Jan 18th, 11, 2:31 PM
Thank you for getting the thread back on the rails! ;)

Sorry if it came out that way it was not my intention to dismiss that thread at all,, it is a worthwhile read from some very sharp guys. ;)

If you read the complete thread there was a little info regarding heads in there too so not totally off track,,,, but it was primarily regarding blocks

Plus the "rails" around here tend to run off course quite a bit which is not all bad as long as the info is good :cool:

It sometimes seems we learn more going down the wrong track than the intended one,, :D

GRN69CHV
Jan 18th, 11, 3:10 PM
One nice feature of alum heads is ease of mods by the home hobbyist. You can clean up a set of alum heads in no time.