Heads...Alum or iron?

[Eagle85C4]

If given the choice what would you rather have, given all options the same...Aluminum or Iron heads?

 

[Ken]

Each has its own advantages and disadvantages; the iron heads retain heat better and therefore aid in the combustion process, while the aluminum heads are lighter. I think what it boils down to is based upon what service in which the engine is to be used. Drag racing and road racing applications would necessitate aluminum because of the advantage of light weight, whereas if you were pulling a sled in competition, or hauling heavy loads, the iron heads would benefit you better. Of course, I don't know squat really.

_ken

 

[Eagle85C4]

Ken....what a load....you are da man...the Guru.....:BOW

Thanks for the answer....now what about a daily driver that might...just might get the occasional romp when faced with a rustang or ricer????


Actually I have a shot at low mile alum heads off a vette or 64cc big valve 195cc runner iron....I just may get both and start a build up of a spare in case my original engine decides to take a vacation south...

 

[Ken]

For a daily driven street machine the iron heads would suit your needs just fine, and you'd save some bucks in the process. Iron heads may not be a dime-a-dozen, but they are certainly cheaper than aluminum heads.

I found this on Keene Bell's web site:

CAST IRON HEADS vs. ALUMINUM HEADS?

In 1960-'61, my 308" 6 cylinder 1953 Hudson Jet held the NHRA record at 94.8/14.70. The cast iron head would run .1 sec/1 mph (10HP) better than an identical aluminum head. It also ran 20° cooler. An engine makes HP from heat. Aluminum dissipates heat more easily than cast iron - into the water jackets. The more things change the more they stay the same. Both heads make HP, but cast iron will always make more.

_ken

 

[Eagle85C4]

Like Family Feud.....Good Answer....

Thanks Ken...

 

[Hrtbeat1]

Double hump (camelback)

So I should use the set of old camelback heads for my 383 daily driver vs. a set of new aluminum heads? Im thinking a TPIS miniram with these heads on a solid 4 bolt main. Just gotta find the right ECM. Maybe 69MYWAY could help there.

Ive seen the flow numbers and have the charts here somewhere. These heads are almost identical to the LT1 heads as far as HP and torque. HHHHMMMMMM wonder if a LT1 ECM would do the trick? Any thoughts?

Thanks Guys

 

[Eagle85C4]

You may want to talk with Moderator Jeff who burns custom proms for ecm's instead of swapping ecm which can be a chore...

 

[netnarc2]

When I went to a Corvette supply specialty store, I told the guy it was an '85 Corvette. "Oh yah, those are the ones with the iron heads. They're heavier than the aluminum heads, but they're stronger." I'll save my money and keep the iron heads. Use the money to buy something else for the car when it's needed in MHO.

 

[sothpaw]

iron will last longer...

I just learned in Metallurgy class:

Any Body centered cubic metal, like iron, will have what we call an endurance limit stress
associated with it. If you don't exceed the endurance limit, the part will last infinitely many
cycles before fatigue failure.

Face-centered Cubic materials never have an endurance limit. Any alloy with an Aluminum
or Copper matrix, for example, won't. At some point, they will fail in fatigue.

... So for engines, I don't know how many cycles you see and at what stress level, but
Iron has the potential to out last Aluminum because there's no stress low enough for
Aluminum to have infinite life.

 

[Ken]

Thanks Southpaw, I'd forgotten about that part, though I'm not sure how much the heads are affected by that particular stress factor.

Other parts, such as anything in the rotating mass, will obviously be affected, but a structure that is securely bolted, as the heads are, may not be as compromised. I don't know. :confused

_ken

 

[sothpaw]

heads

You have to look at each part separately, and see what the operational stresses on it are,
and whether these are repetitive in nature or only very occasional.

I would think the heads see some stressing due to the combustion when the cylinder's fire.
But combustion is not my thing.

 

[netnarc2]

I think the most important consideration regarding heads is HEAT. Usually when an engine over heats to an extreme degree, one of the first things that get damaged is the heads. They'll warp or even crack from excessive heat. Of course, a blown piston or dropped valve will also cause damage to a head, but that's not because the head itself failed. It got smacked by something that wasn't supposed to hit it. Overheating can also damage the engine block, cracking it, causing the freeze plugs to fall out, causing the whole engine to sieze up.

 

[sothpaw]

heat...

... if it is a changing temperature distribution, might cause
cyclic thermal stresses, which would cause fatigue.

None of what you mentioned happens much. Fatigue takes
1 million cycles to be a problem if the part was well designed.

 

[WhalePirot]

I chose the Dart Pro II heads, in aluminum. My builder referred to the better heat dissipation which allowed a point higher combustion than identical cast iron heads.

I don't especially like the softer material for bolting things to the aluminum, however. I am not sure the weight savings means much to me.

Car runs kinda good, tho .


Mike

 

[echoecho11]

Eagle I have found that there is a fue clues as to the ansser to this question... in 1986 Corvettes I beleave were offerd with eather Alu. or Iorn heads. The Alu. head engine was rated with higher HP. 1987 to pressent all corvettes came with Alu. heads. the new LS1/LS6 C5 vettes also have Alu. blocks. I have been following Car Craft Mag's Engine Masters Series. last year they had the 50 top engine builders compette to build small blocks. they did'nt show all 50 of them but the top 10 all had Alu. heads on them. Part of the cryteria for these engines was to use parts that was obtainable for the average joe. I E no exotic stuff. nice engines that averaged + 500HP and + 500FPT from 2,000 to 6,500. one of the top ten was a 307 based sbc that had L98 corvette Alu. heads . I beleave that it was Bruse Crower's son or grandson that built it. Bernsteen and Force have Alu. heads on there 6,000 HP top fuel engines so I,m shure Alu. is up to the job. I have heared that the iron Vortec heads can make good power on a budget but the fast burns are better. 92 Lt1's was the first that I seen the Vortec type combustion chambers. these Alu. heads had provisions for revers cooling so they wont fit on your 85. now here is the quistion that I have? With the proliferation of cast Alu. parts.... Why do they charge so much for them? Alu. might cost more but it is easer to machine and asembly would be the same? And the last clue might jest be....? What kind of heads does Ken have on that "Cool" 87 silver 400+ CI cope ? Can't spell worth a s--- can I ? :Silly

 

[Mad-Mic]

racing top alcohol dragsters with 4000+ hp i can tell you aluminum heads are the only way to go! if built right the heads RARELY fail at 12,000 rpm shifts. mostly what fails is a spun main bearing which gets ugly. good thing about aluminum though, most of the time it can be repaired with an aluminum welding job. downside to street heads are don't run it low on water and seriously over heat the engine then pour cold water in the radiator. it will warp the heads and sometimes you don't need to pour the water in for this to happen. just over heating it will warp it.

JFYI

 

[Edmond]

I would go with aluminum. It's lighter and easier to work with right? And given todays constant increase in aluminum technology, I'd say there isn't as much to fear in terms of it failing as in past years.

 

[echoecho11]

Edmond what about the suspention on are C4,s..... lots of ALU. there. I would think that these parts fall under the catagory of stressed parts? they take all the banging around (stress) that us nuts in are 31-3200 lbs cars dish out. think of the stress that the front spindels(ALU.) must handel when brakeing say 70mph to 25mph and then back on the troddel and the rear careires (ALU.)hold the weight of car as it climes back to 70mph with a copel hundred horse power pushing hard against your ALU. fore link suspention. Mine are 12 years old this year your's are even older? I got my vette out for easter yesterday, I think I may need a srienk as I get excited when I drive this car.Now I'm not going to tell you that I been brakeing the law but I would like every one to know that all my ALU. parts held up great. I spent 16 years of my life working on fighter jets for uncle sam, these jets have alot of ALU. in them. one jet that comes to my mind is the F4 phanom. Its techknowage was developed in the 50's and this jet was used into the 90's. their should be no argument that these jets see much more stress than are vettes will. So the use of Alu. is old hat. The new kid on the block ? Carbon Fiber, Titaneaum. concluding that the only reason that Iron heads are used on mass produced cars is they are cheeper than Alu. If I had a vette with Iron heads on it and I was happy with the way it ran and I did not want it to run better I would not take them off.:TALK

 

[Edmond]

Echo,

The only reason you'll need a shrink is if you don't get excited from driving the car! You bring up a good point though, aluminum has been around for quite some time and the new things like carbon fibre and titanium could someday do to aluminum what aluminum has done to iron.

 

[SlowRide]

In my view the LT-5 is an excellent example of the durability of aluminum. Those beasts are virtually bullet-proof. IMHO

Nick