What are the differences between cast iron heads and aluminum heads? Why does everyone suggest that aluminum heads must be changed to cast iron?
You mean just the opposite in regards to the change in general right? Aluminum heads offer a considerable weight savings over cast iron ~15 lbs ea lighter in regards to the 2.8 series from my measurements years ago. In regards to performance, they generally offer mild to moderate resistance to spark knock in performance applications although much of that has to do with combustion chamber science which in the case of the 2.8 would be a moderate improvement given how old the iron 2.8L head and chamber design is. Having experience with them I would not choose iron heads over aluminum without a definite benefit to be had.
[This message has been edited by Joseph Upson (edited 05-22-2016).]
Anyone suggesting replacing aluminum heads with cast iron, fell off their rocker and bumped their head.
Aluminum gets the heat away from the chamber faster than iron does. Almost all aluminum heads also tend to be better designed than similar cast iron heads. The only reason to stick with cast iron heads is if it's what your engine came with, and you aren't trying to get the best power/efficiency out of it, or just can't afford to switch to aluminum heads; or they just don't exist for your engine.
If cast iron was actually better, every manufacturer would still be using it in every engine, because it's cheaper.
Actually, the suggestion was to replace aluminum heads with cast iron heads. I got the sense, from my sixth sense, that there was a problem with fit of the manifold. I don't see how that would be an issue but some seem to think there is some issue. Maybe they don't want to get beaten at the stop light grand prix.
The only reason to replace aluminum with cast iron would be to use the Fiero intake manifold on a block that came with aluminum heads. The aluminum heads would also require the newer style intake manifold...which won't work with a distributor...etc.
Now it's clear. But it will lead to more research to get around that, like a distributorless ignition. I'm sure it's been done at least with swaps to larger V6s.
Money is no object. It's just a piece of plastic.
[This message has been edited by lyleap-gmc (edited 05-22-2016).]
Anyone suggesting replacing aluminum heads with cast iron, fell off their rocker and bumped their head.
Aluminum gets the heat away from the chamber faster than iron does. Almost all aluminum heads also tend to be better designed than similar cast iron heads. The only reason to stick with cast iron heads is if it's what your engine came with, and you aren't trying to get the best power/efficiency out of it, or just can't afford to switch to aluminum heads; or they just don't exist for your engine.
If cast iron was actually better, every manufacturer would still be using it in every engine, because it's cheaper.
If you cast both from the same mold the iron makes more power.. every time..
What are the differences between cast iron heads and aluminum heads?
I've seen this topic here many times before... why a new topic?
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Originally posted by lyleap-gmc: Why does everyone suggest that aluminum heads must be changed to cast iron?
Where is this suggestion coming from?
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Originally posted by lyleap-gmc:
Have I started an aluminum vs iron war?
[/quote] Being you have so few posts, I'm wondering if that wasn't the point? Why post the question when you have seen these suggestions elsewhere? What's your take in this?
I have an '85 Fiero with an engine that is supposedly bad. Spun a rod bearing. I have an '89 Olds engine that has aluminum heads. I wondered what is needed to make the Olds engine work in the Fiero.
I didn't intend to start any wars. They get in to too many opinions and very little fact. You know about opinions.
So...it is the exact case that I suggested. Switching back to iron heads on that engine could cause odd compression ratios...I don't know the specifics of that engine, so it might work, but you definitely want to verify it. But if it doesn't, it could be an almost direct short block swap for your car.
Or...you could keep the aluminum heads and Olds intake. Top it off with a 7730 ECM swap to run distributorless (and that might be what is already on that Olds engine). Then you might be running into some coolant and fuel routing issues...and of course the wiring for the swap.
Personally, I would go with the iron heads and Fiero intake on that short block...and if the compression ratio prevents that, I would look for a different engine to swap in.
The question that arose was why the need to change the heads from aluminum to iron. That was the reason for the original post. There was no explanation of the reason for changing the heads in any of the postings I read. Just change them. It seemed a bit like changing a working light bulb.
Now I have some answers.
Now I need to examine closely what I have and what I will need if, indeed, the engine now in the Fiero has a bad bearing.
Thank you all for your patience and consideration.
There are 2 main reasons people put the Fiero top end onto the other V6 engines:
1) To keep a stock looking engine 2) Not willing to make custom fuel lines, coolant lines, etc
If you're willing and able to tackle stuff like coolant hoses, fuel lines, and an ECM swap, then keep the aluminum heads. They have more performance potential.
[This message has been edited by Blacktree (edited 05-22-2016).]
I have an '85 Fiero with an engine that is supposedly bad. Spun a rod bearing. I have an '89 Olds engine that has aluminum heads. I wondered what is needed to make the Olds engine work in the Fiero.
I didn't intend to start any wars. They get in to too many opinions and very little fact. You know about opinions.
Get in touch with forum member RobertISaar, he's a mastermind regarding the GM ECM coding and computer magic in general. He maybe able to assist you in getting the proper ignition angle settings in the chip adjusted so that you can run that engine with its DIS ignition system using the Fiero ECM, requiring that you make the appropriate sensor plug changes instead of doing a rewire. The spark advance tables would need to be adjusted down some as the iron heads require more advance for lightoff than the aluminum heads.
That is what has been accomplished with the 747 ECM using the Syclone/Typhoon code mask which is setup to run a distributor from the factory, but used for the modified code version under the name "Code59" to run DIS ignition systems (such as mine) properly.
I know some people on here have started custom intake manifolds for Fieros- Has anyone ever thought of creating a lower intake that would adapt the upper fiero intake plenum to the aluminum heads?.....It seems that would be a great idea....And yes, I know that the upper intake would also need to be modded at the pinch point and the comp ratio would need adjusting!
It just seems like a natural to allow the newer design with the original look.....I'm probably crazy!
There are 2 main reasons people put the Fiero top end onto the other V6 engines:
1) To keep a stock looking engine 2) Not willing to make custom fuel lines, coolant lines, etc
If you're willing and able to tackle stuff like coolant hoses, fuel lines, and an ECM swap, then keep the aluminum heads. They have more performance potential.
Agreed. Using a complete aluminum head 3400 DIS engine would be the same work as a complete engine swap, with attendant modification to fuel lines, cooling hoses, new ECM/wiring harness modification, and new headers/exhaust. https://www.fiero.nl/forum/Forum2/HTML/111290.html
You may as well go with the 3800 S/C swap if you're going to do that much work.
My GT is a 3400 block/Fiero heads hybrid because I wanted the stock look and it was less work. I added the S/C to overcome the limitations of the iron heads/Fiero intake.
If I were "doing over" I'd be looking for a 3800 S/C...
3500 and 3900 V6's can top 270 WHP with the right mods while being ~75lbs lighter than a 3800SC. All but the last generation of 60 degree V6's bolt up to the stock Fiero engine mount brackets and can use a stock Fiero flywheel. Plumbing the latest generation is actually *EASIER* than stock because the LZ4 3500's and 3900's have the coolant outlet on the driver's side while the water pump and coolant inlet are still on the passenger side... there's no need for a cross-engine coolant pipe.
[This message has been edited by Will (edited 05-23-2016).]
I took a closer look at the '89 engine and is has a plug where the distributor would be. I don't know if there is a gear on the camshaft. More research to do.
It had the DIS ignition but there are no notches in the harmonic balancer as has been indicated in some postings about changing to DIS. And more research to do.
I took a closer look at the '89 engine and is has a plug where the distributor would be. I don't know if there is a gear on the camshaft. More research to do.
It had the DIS ignition but there are no notches in the harmonic balancer as has been indicated in some postings about changing to DIS. And more research to do.
That distributor plug has a gear and the notches for the ignition system are cut into the crankshaft. The crank sensor is in the side of the block. The balancer sensor is not applicable to all similar engines of that year and later and is not used directly by the DIS module, so if it is not present its one less headache.
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Originally posted by Will: ... Plumbing the latest generation is actually *EASIER* than stock because the LZ4 3500's and 3900's have the coolant outlet on the driver's side while the water pump and coolant inlet are still on the passenger side... there's no need for a cross-engine coolant pipe.
The 3900 is an exception here Will. It has "U" shaped coolant flow so the outlet is also on the passenger side in nearly the exact same location as that for the Fiero 2.8L however, the stock crossover pipe bends cause interference requiring modification or replacement.
[This message has been edited by Joseph Upson (edited 05-24-2016).]
I took a closer look at the '89 engine and is has a plug where the distributor would be. I don't know if there is a gear on the camshaft. More research to do.
It had the DIS ignition but there are no notches in the harmonic balancer as has been indicated in some postings about changing to DIS. And more research to do.
As mentioned above, the notches are on the crankshaft. There's actually a metal disc built into the crankshaft with the timing notches cut into it. The crankshaft position sensor on the side of the engine block points at that timing disc.
It doesn't have a distributer, but still needs to drive the oil pump. Remember, the oil pump is driven off the bottom of the distributer shaft on the 2.8 V6. So there's actually a short shaft under that plug, with a distributer gear and the oil pump drive. It's basically the bottom half of a distributer. So yes, the camshaft will still have the distributer gear on it. However, you'll find that the intake manifold on the newer engine will interfere with the distributer, if you try to install a distributer on it.
IMO, you'd be better off keeping DIS on the engine, and modifying the ECM software to work with it. Plus, DIS is more reliable and more robust than a distributer, as well. This is especially true in the case of the 2.8 V6, where the ignition module in the distributer is infamous for failing.
[This message has been edited by Blacktree (edited 05-24-2016).]
I don't see the advantage of aluminum heads -- don't they warp at high temps.
As far as saving weight, a few pounds on street car does not do much. If you at the track, go to a half tank of gas and empty the windshield fluid bottle, if you are that inclined.
I don't see the advantage of aluminum heads -- don't they warp at high temps.
As far as saving weight, a few pounds on street car does not do much. If you at the track, go to a half tank of gas and empty the windshield fluid bottle, if you are that inclined.
High temps? Like what? In any well-maintained street car the heads are not going to see temps high enough to warp them. It is not a concern.
Weight loss on a street car does plenty. Physics don't change because you're on the street versus on a track. Weight loss in the engine will lower the CG slightly, and move the front/rear balance slightly closer to 50/50. That can equate to slight improvements in handling, acceleration, braking, and fuel economy. Add in weight loss from other things and the improvements can be even better.
Blacktree - Thanks for reminding me of things tucked away in the dust bunnies of my mind. I am leaning heavily toward a DIS system on the 89 engine. Far less hassles with the engine itself. The ECM may get to be some research and work.
I agree with Dobey. If the cooling system is operating correctly cylinder head temperatures should not be a problem. The car won't be a daily driver but will get used solely on the street and highway. I could lose 20 or 30 pounds and that would help the car a lot.
Originally posted by lyleap-gmc: Blacktree - Thanks for reminding me of things tucked away in the dust bunnies of my mind. I am leaning heavily toward a DIS system on the 89 engine. Far less hassles with the engine itself. The ECM may get to be some research and work.
I agree with Dobey. If the cooling system is operating correctly cylinder head temperatures should not be a problem. The car won't be a daily driver but will get used solely on the street and highway. I could lose 20 or 30 pounds and that would help the car a lot.
The aluminum heads offer more than just a weight savings, they also offer benefits associated with the combustion science applied to their design, they are more efficient in that they can achieve better performance returns when pushed to the upper limits of pump gas octane ratings. As has been mentioned already, the thermodynamic qualities and combustion chamber design are pluses over the old iron heads. At one time I bought into the cracking theory but it was more the result of hearsay than actual experience. If an aluminum head cracks today, it's likely because it was run far hotter than any cylinder head should have been. Aluminum cracks, iron warps and they both end up at the machine shop or on the junk pile.
I've run my engine to near 300 deg trying to nurse it home before a leaky radiator went dry. The aluminum heads were fine. The rod bearings took a hit because the already thin oil (5w15) I was experimenting with got even thinner dropping the oil pressure too low.
The aluminum heads for the 60* V6 offer several pluses- Canted valves, better intake and exhaust passages, better quench/combustion chamber design, aluminum transfers heat away from the chamber better...And the lower weight improves the weight distribution- the norm for a Fiero is around 43/57- the best weight distribution is around 47/53....Although there are varying opinions on that. A 3400 is approx' 50 lbs lighter- That's almost 2% of the Fiero's weight, and taking 2% off the back will shift the distribution approx' 1%.
I still think that someone should make a conversion lower manifold to allow these aluminum heads with a (Modified) Fiero upper plenum.....
And the only reason my Fiero ever overheated was because I once made the mistake of installing a water pump with a plastic impeller- big mistake!
The aluminum heads for the 60* V6 offer several pluses- Canted valves, better intake and exhaust passages, better quench/combustion chamber design, aluminum transfers heat away from the chamber better...And the lower weight improves the weight distribution- the norm for a Fiero is around 43/57- the best weight distribution is around 47/53....Although there are varying opinions on that. A 3400 is approx' 50 lbs lighter- That's almost 2% of the Fiero's weight, and taking 2% off the back will shift the distribution approx' 1%.
I still think that someone should make a conversion lower manifold to allow these aluminum heads with a (Modified) Fiero upper plenum.....
And the only reason my Fiero ever overheated was because I once made the mistake of installing a water pump with a plastic impeller- big mistake!
As far as fully dressed motors go, I think there's only about a 20lbs or less difference since the 3400 intake overall is larger than the Fiero's and it's accessory system also adds weight over the Fiero's 2.8 system. Practically speaking, there's no real reason to do a full 3400 swap when you can buy premade parts to make a 3800[SC] swap almost plug&play.
I keep forgetting that most Fieros have a lot of accessories- I have an Alternator- That's it. If I swapped engines I'd probably use the steel pan and 2.8 front cover. And I thought that the intake on any of the later V6s was lighter than the L44 intake- That thing is ridiculously heavy for what it does. The smaller starter is almost 10 lbs lighter also- But that can be retro-fitted to almost any engine.
On the "Dreamer" side, I know a guy who has a 60* V6 in a Europa, of all things; He has an Aluminum block......Now that would make the back end lighter.
I guess I just don't see the overall benefits of aluminum and if you are talking high performance, maybe, but even real high performance you wanted the added strength of iron and steel. Aluminum is used because it's light, not strong. And, on a limited budget I would not invest my money in aluminum heads to save a few pounds (the returns are too minimal).
Curious, what do top fuel dragsters use? (I may be wrong, but I know there are alloys out there.)
They have solid (no water passages) aluminum engine blocks, along with cylinder heads. Amazingly the whole engine weighs only 500lbs. Remind you these things make 10,000+ HP!!!
So aluminum in the extremes may have some benefits but I cant afford it!!!
I guess I just don't see the overall benefits of aluminum and if you are talking high performance, maybe, but even real high performance you wanted the added strength of iron and steel. Aluminum is used because it's light, not strong. And, on a limited budget I would not invest my money in aluminum heads to save a few pounds (the returns are too minimal).
Curious, what do top fuel dragsters use? (I may be wrong, but I know there are alloys out there.)
Top Fuel dragsters use aluminum for the block, heads, and blower. I don't recall what alloy is used for the pistons or rods.
Aluminum isn't used only because it's lighter.
Also, the OP wasn't asking about spending $$$$ for aluminum heads to put on an engine that came with iron. The question was about replacing aluminum heads on the newer V6 engines, with the iron heads from the Fiero. The later generation aluminum heads on the 3x00 V6 engines are far better than the iron heads on the 2.8.
Originally posted by RotrexFiero: So aluminum in the extremes may have some benefits but I cant afford it!!!
While there might not be any readily available aluminum heads to throw onto the 2.8, saying you can't afford aluminum because top fuel dragsters use it, is just silly.
GM has been using aluminum for decades. If you can afford a Series III 3800, then you can afford a 3400/3500/3900 V6 which has aluminum heads.
The newer Aluminum heads for 60* V6s; Canted valves- They move away from the cylinder wall to allow better flow....The heads flow better everywhere else also. The quench is a better design(Quench makes a 2 valve burn fuel more efficiently- basically creates turbulence just as the piston tops out and the ignition fires- better mixing and spreads the flame front thru that mixture. The aluminum transfers heat away from the chamber and into the water jacket better also.......Oh yeah, the aluminum heads are lighter, too!
There is a reason that all performance engine go to aluminum heads- And only a small part of it is light weight.
I got the sense, from my sixth sense, that there was a problem with fit of the manifold. I don't see how that would be an issue but some seem to think there is some issue. .
This brings to mind that aluminum and iron expand and contract at different rates, some say it can lead to leaks. But I have never had such a problem on any engine.
If you cast both from the same mold the iron makes more power.. every time..
not really, the same casting makes about the same power, sure you could argue less thermal losses through the iron, but the reality is, that side by side tests don't show an appreciable difference in either material the real difference in power comes from design.
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Originally posted by lou_dias:
As far as fully dressed motors go, I think there's only about a 20lbs or less difference since the 3400 intake overall is larger than the Fiero's and it's accessory system also adds weight over the Fiero's 2.8 system. Practically speaking, there's no real reason to do a full 3400 swap when you can buy premade parts to make a 3800[SC] swap almost plug&play.
It's a case of the ends justifying the means.
yeah, but with a 3x00, the timing cover and water pump are all one piece, there is only one bracket, and one tensioner. the design is simpler, and almost certainly lighter than the fiero accessory drive by a mile. to go along with that, as Will stated, there is no longer a need for a crossover pipe for the cooling system, the intake manifold is simplified by having only an upper and lower, not a plenum, middle intake, and lower intake like a stock 2.8. not to mention, for what they are, the stock fiero intake castings are very heavy.
if you use a stock fiero manual transmission, you don't need to make(or buy) new mounts at all, the stock ones bolt up. hell, you could do it with the stock auto too, but ewww gross.
------------------ "I am not what you so glibly call to be a civilized man. I have broken with society for reasons which I alone am able to appreciate. I am therefore not subject to it's stupid laws, and I ask you to never allude to them in my presence again."
The material is irrelevant but in our case the material is directly related to 2 different designs.
Gen2+3 motors need a design that would fit under a low profile FWD hood. Canted valves and runners that didn't rise at 60 degrees achieved this. The AL lower intake is much larger than the Fiero stock lower because the path is flatter hence the intake is much wider and much of that added path length replaces the Fiero middle intake.
LS3 and LS7 heads are made of aluminum but their design resembles Fiero iron heads. The exhaust ports are D-shaped but you could also make Fiero heads D-shaped. In this case the canted design forced the flat part of the D to point in various directions where as on the LSx heads they are all down on the same side making header design simpler. You could grid the Fiero ports into a similar D shape...however the ports can be safely bored round to 1.25" so that would only be necessary if you wanted even more flow. Even the combustion chamber resembles the iron head design. "canted" is not a performance advantage.
As for the valves themselves, the AL heads use thinner valve stems. The valve stem is an obstruction. Foreign engines use real skinny stems (typically). The Fiero Store SSI valves are narrowed where the air flows around the valve to match that thinner diameter increasing flow over stock Fiero valves. Also, you can use the 1.76" intake valve with the appropriate valve guide and then radius the port to match the valve for increased flow.
The material is irrelevant but in our case the material is directly related to 2 different designs.
Gen2+3 motors need a design that would fit under a low profile FWD hood. Canted valves and runners that didn't rise at 60 degrees achieved this. The AL lower intake is much larger than the Fiero stock lower because the path is flatter hence the intake is much wider and much of that added path length replaces the Fiero middle intake.
LS3 and LS7 heads are made of aluminum but their design resembles Fiero iron heads. The exhaust ports are D-shaped but you could also make Fiero heads D-shaped. In this case the canted design forced the flat part of the D to point in various directions where as on the LSx heads they are all down on the same side making header design simpler. You could grid the Fiero ports into a similar D shape...however the ports can be safely bored round to 1.25" so that would only be necessary if you wanted even more flow. Even the combustion chamber resembles the iron head design. "canted" is not a performance advantage.
As for the valves themselves, the AL heads use thinner valve stems. The valve stem is an obstruction. Foreign engines use real skinny stems (typically). The Fiero Store SSI valves are narrowed where the air flows around the valve to match that thinner diameter increasing flow over stock Fiero valves. Also, you can use the 1.76" intake valve with the appropriate valve guide and then radius the port to match the valve for increased flow.
Here are pics of LS7 heads.
you can't really be comparing LS7 heads to fiero heads... Gentlemen, he went full retard.
and yes. canted valves are an advantage, just because they aren't used on an LS7 doesn't mean they aren't an advantage, they allow for less aggressive of a turn into and out of the cylinder.
jesus man, how can you even make that comparison, did you even look at the combustion chambers?
[This message has been edited by ericjon262 (edited 05-27-2016).]
So LS7 design, which is newer than GEN3 doesn't use canted valves and you claim canted is a performance advantage where it was really nothing more than getting it to fit in a low profile package.
Next time you say retard, do it looking in the mirror.
Are Seried 2 or 3 3800SC valves canted? No. Get over it.
[This message has been edited by lou_dias (edited 05-27-2016).]
Originally posted by lou_dias: So LS7 design, which is newer than GEN3 doesn't use canted valves and you claim canted is a performance advantage where it was really nothing more than getting it to fit in a low profile package.
Next time you say retard, do it looking in the mirror.
Are Seried 2 or 3 3800SC valves canted? No. Get over it.
Are the Gen V heads ilnine? No. Get over it.
Cylinder heads aren't as simple as you seem to be. Don't trash yet another thread with your facile nonsense. The OP's question was about the Fiero 2.8 heads versus newer 60 degree aluminum heads. The aluminum newer generation 60 degree heads are far better than the 2.8 heads, regardless of material. Being aluminum is an added bonus, because the thermal properties of the material are better, and it's easier/faster/cheaper to machine than cast iron heads are. ∎
Just a bit of info on canted valves; Valves flow around the edge- the curtain as it is called. As valves get bigger to have more curtain- and more flow- they start to approach the cylinder wall which blocks off some of the curtain. By angling the valves, the valve head moves away from the cylinder wall and so flows better. Most chevy small blocks have all of the valves mounted at a single angle- 15* is one figure I remember. That helps a lot, but the poly-angle valve heads flow a bit better. Not only does the 60* V6 use poly-angle, but also the BB Chevys, and the 429-460 Ford and 351 Clevelands used Poly-angle valves. One problem with manufacturing poly-angle heads is the extra machining at different angles- It costs more. That is probably why the LS/LT engines don't use poly-angle.
The younger people on here may not remember this, but the Ford 351 Cleveland 4bbl engines had poly-angle heads that flowed really well- So well that back when NASCAR was still running big blocks, Ford found they could actually get MORE power out of a 351C than a 429- They would run 8000 rpm and would only last for qualifying- During the actual races they would use the lighter-loaded big block for longevity, but the 4BBL cleveland put them on the pole quite often- The qualifying 351s were referred to as "Grenades"!
One last little bit of info; The stock 351C 4BBL 2-valve heads flow better than the new 5.0 Coyote 4 Valve heads on the intake side- the exhaust sucks because the old Mustangs had the big spring towers so the exhaust had to make a tight turn to clear them- You can port them and use headers tho.
Originally posted by cvxjet: One problem with manufacturing poly-angle heads is the extra machining at different angles- It costs more. That is probably why the LS/LT engines don't use poly-angle.
The new Gen V LT engines do use different angles for intake and exhaust valves. It's the only way to use the same heads with larger valves on both the large bore blocks like the LT1/LT4 6.2, and the small bore blocks like the 5.3. Likewise, all the Gen IV 4.8/5.3 engines use the same cathedral port heads as the LS6/LS2/LS4 engines did, rather than the newer and higher flowing square port heads on the LS3/L92 and other larger bore Gen IV V8s after 2008.
