I don't have any ability at the moment to compare these heads; I would love to get the aluminum, poly-angle heads on my stock (Appearing) Fiero engine....I believe there are too many differences, but those newer heads look like a great improvement....Any knowledge on what the compatability is? Comp ratio, water passages, intake offset....It would be nice if someone made a lower manifold that adapts the newer heads with the original intake upper pieces(Yes, I know the upper would need improvement!)- noone makes after-market heads, and the beauty of these is they are readily available.

Well i think the 3500 heads would bolt on to the 2.8 as long as the heads came from the first gen 3500 and not the ones that share the 3900 block as i think they increased bore spacing but even if you could put the heads on you will need to do so much it would be better to just start with the 3500 as it is just a better engine

As mentioned above, the Gen-3 heads (3100, 3400, early 3500) will fit the 2.8 block. But they come with a lot of baggage, so to speak.

First of all, the aluminum heads have much smaller combustion chambers than the iron heads. So the compression ratio will be absurdly high, unless you use dished pistons. You can swap in 3.1 or 3100 pistons, which will also require a crankshaft swap (from a 3.1, 3.4, 3100, or 3400), and a neutral-balance flywheel. If your 2.8 is from an '88 Fiero, then your flywheel will work. Otherwise, you'll need to swap it.

Also, the 2.8 manifolds (intake and exhaust) will not fit the 3x00 heads. So you'll need to use 3x00 manifolds.

To make a long story short, you'll basically end up replacing everything but the 2.8 block and rods. Since your Frankenstein 2.8 will have the 3x00 top end on it, you'll end up doing some of the same things you'd be doing in a 3x00 swap (custom intake and exhaust piping, fuel lines, coolant hoses, dogbone mount, etc).

On the other hand, you could swap in a complete 3x00 engine. You'd be doing much of the same stuff, except you won't need to piece together an engine. Instead of building an engine, you'll be modding the lower motor mount bracket, and doing some wiring. And the 3x00 engine will make more power / torque than the Frankenstein 2.8.

Just a thought.

[This message has been edited by Blacktree (edited 09-10-2015).]

Thanks for replying; I was able, after a lot of searching, to get a top-view pic of the two different heads and compare- and yes, they are completely different....To get an aluminum head with fast-burn chamber and splayed valves would be a dream come true, performance-wise, But I guess the plan now is to get a 3500- That'll take 50 lbs off the back and run pretty dang hard- but I'll have to wait until I move to Trinity county- They don't have smog checks there...I want it to be fully smog legal- but GM never put a manual trany in with the 3500 and that won't fly in CA- and the 3900 has a longer stroke(More torque, but less revy(?) and that enormous vari-intake, which adds weight and that weight is up high. I'd love to keep the stock look- well, maybe lose the stupid egr-which sticks up in front of the engine rather than under the intake like on old engines.....I'll just have to satisfy myself with a red intake manifold.....

The variable intake will probably only add a few pounds. I'm pretty sure it's just aluminum, or maybe plastic.
After the engine is installed, you could probably swap the upper intake for the 3500 upper, or the one from the 3900 Impala. (Looks just like the 3500.)
The variable intake can be turned off in programming.

At some point I'm planning to install a 3900 from an Impala, using a manual trans, with the G6 programming (or something like it.)
I would use one from a G6, but they tend to be much less common then the one in the Impala. The horsepower rating is the same for both 3.9s, at 240.

[This message has been edited by Raydar (edited 09-12-2015).]

Thanks Raydar.....I really liked the idea of the short-stroke 3500- But I don't know if it's more of a winder than the 3900- I have that engine in my (ACK!) Uplander- It gets great mileage(29 HW, 20 towing my boat), but it runs kinda rough, especially the idle. Of course, technically, the 3900 is the end developement of the 60* V6, and as such is the engine that would supposedly have gone in the Fiero at some point- Although, also of course, there would possibly have been a push to either lighten/2L-4 or enlarge and uprate, possibly getting an LS V8....With the incredible performance of the Z28, which has beaten the new Stingray at a number of tracks, there might have been a willingness to allow Pontiac to take the Fiero to a much higher level of performance.

As far as Manifold weights- I am always taken aback by the weight of the 2.8 L44 intake- 27 lbs.....How the H--- did they get the weight up that high, and yet it has that stupid pinch point in it....The LS plastic manifold weighs in at 7-9 lbs. The 3900 vari-manifold is pretty big, and yes, the actual varible part is a plastic flapper valve, but has the actuator, also. They went ahead and redid the 4.3- based on the LT V8 structure- It would have been nice to see the next gen 60* with aluminum block, etc....To get the engine weight down to 300 or less, and still have the PR low center-of-gravity would have been terrific. Maybe 230 hp @ 6500 from a 3L...I can dream, can't I?

quote Originally posted by cvxjet: As far as Manifold weights- I am always taken aback by the weight of the 2.8 L44 intake- 27 lbs.....How the H--- did they get the weight up that high, and yet it has that stupid pinch point in it....The LS plastic manifold weighs in at 7-9 lbs.

The intake weight is that high, because the aluminum used has a higher density than the plastic used on newer intakes. Go see how much a TPI or LT1 intake weighs. Aluminum is just what was in use at the time, so it's what got used. The technology available at the time only allowed for certain configurations, and the packaging in the FIero only made things worse, since the throttle neck had to clear the distributor. GM has still made crappy intakes on modern engines, as a result of packaging. The LS4 intake has a horrible design, and is the flattest LSx intake there is.

The LSx intakes are more like 12 lbs, not 7. The truck intakes weigh even more.

Dobey, I get your whole post- But I'm just frustrated, because I like the little V6, yet I'd like to take 100 lbs off the backend- That would put me close to 46/54 weight destribution- even before the PWRSTR w/electric pump up front......With my no-options 85 SE V6, I was actually close to 42/58 originally, but I moved the battery and carry some spares(Coil & module, etc) and a tool kit up front, and removed that stupid fan from the trunk- It never ran 'cause I don't have A/C- I'm actually going to remount it behind the scoop on the right lower-IMSA type, then duct it along the firewall to the dist'.
I remember My Father bought a Cutlass w/3300- It had a plastic manifold- I was so envious...Yes, I know, one fire and that plastic mani' is gone, but the lightness, and the smoothness of the passages- I am actually amazed that they even gave the 3500-3900 variable cam timing. By the way, the 460 Ford in my Jet boat has an enormous dual-plane intake that only weighs 24 lbs! The Ford FE(390, 427, 428, etc) had an intake similar to the 60* V6- part of the head/Valve cover surface, and the IRON ones weighed- 75-85 pounds!
You guys should be made aware of something- I bought a Comet GT in 77- and Ford cancelled it....I bought a Fiero, and GM cancelled it.....I bought a 99 Formula, and they cancelled it, too....If I like it, they will cancel it.....Happens with those Frozen dinners, candy, etc........I gotta believe that they scan what I like and someone, somewhere, is tallying the info and deciding what things I like and cancelling them....Maybe I'm paranoid, but geez! (It's not paranoia when they ACTUALLY are out to get you.....)

[This message has been edited by cvxjet (edited 09-12-2015).]

Well, it's just money. There are options available to go to an aluminum block/heads. If you really want to keep the 2.8 top end to look stock and lose weight, all it takes is money and time.

I'm hoping to have my LS4 weigh less than the 2.8 does, when I get it finished. If I can get it down to 300 lbs, that'd be great.

I wish that GM/Buick hadn't sold the 3.5 V8 to the British- when the Fuel crisises started in the 70s, that would have been a great engine, and we'd have a million of 'em in the JYs- probably redesigned for transverse mounting...To me, that would be a great engine- but the LS4 is also a great engine-like it was made(Basically) for the Fiero. And I have seen a hens tooth- A guy I know(thru Mike Maiers-Check out his NASCAR-engined, pushrod suspended 66 Stang on line) has a Lotus Europa, with a 2.8 in it- with an aluminum block.....If money were no object! $4000- if you can find one!

Sadly, I am slowly becoming aware of my limitations- I wanted a Pantera so bad I could taste it when I was 14-18, but a Fiero with 300 hp would probably be a trip straight to either ticketville or the JY....I drive pretty well, but I found with the 99 Formula, that that much power is one of two things- Too much fun or to much scary- both ways at the same time, sometimes!

I was driving a backroad in my Fiero- Mines road to Mt. Hamilton- Approx' 1/2 hour from the inner bay area, yet its all farm and ranch land- You could easily use it to film a western! - Anyway, my GF and I were up there in the spring, and a guy comes around the corner behind me in a JCW Mini- I was puttering because a Bicyclist was just a few turns ahead- He'd passed when we stopped for a photo-op- and so I putted past the biker, and the JCW took it easy until I passed- then back on my butt- so I said, "game on!" and dropped the hammer- Mind you my GF actually likes going around turns fast(2nd date)....But she didn't like 10-10ths....The JCW disappeared....He had been cranking when he came up behind me....I backed off after SHE created her second new word("OH-F%#&A!!)...maybe a mile or so.....It was a blast, but it's truely not particularly safe...especially with me getting....(Arrrgggg).....old.....Last summer I did a 1.5 gainer off the front of my waterski- with a chest-hand slap...Broke 3 ribs....I really don't remember signing up for this getting old crap!

quote Originally posted by cvxjet: ...They went ahead and redid the 4.3- based on the LT V8 structure- ...

I know you said LT, but do you mean the upgraded LS structure?
The latest LT1 and LT4 are essentially the LS architecture with direct injection and a few other "toys".
This was not to argue. Just asking for clarification.

Either way. I have wondered how that new 4.3 would fit in a Fiero, since the real constraint with the LS block seems to be room for belt driven accessories. The 4.3 would have to be at least 4 inches shorter than the LS, or one would suppose...

Yes, basically it'sa rebop of the LS engines, but now designated as "LT", very much the same except a few improvements- The V8s get the DOD across the board- I don't know if they put that in the 4.3- seems like it would really shake with only 3 giant cylinders running- Yes, most assuredly that engine would be great in a Fiero- But it's not a winder, at all- I beleive it redlines at 5800- But it has a lot of oats- 280 or so HP....I was lookibg for a weight but couldn't find hide nor hair...and weight is a slippery number anyway; Short or long block, with top dressing, accessories, etc. Since it's only used in RWD, you will have to deal with the Starter location problem, tho...Hopefully there is room for mounting it on the left side.

Just as a bit of interesting info, before I stated that the Ford FE engine iron intakes weigh 75-85 lbs; My 460 Ford HEADS only weigh 65 each, fully loaded- that dang intake is a back-breaker! But just think how much weight you could eliminate with an aluminum intake- probably over 50 lbs! And, as far as I can find out, the FEs are the only other engine with the"Partial head- partial intake" design- like the 60* V6, if you understand me. I wonder what the thought process was that arrived at that design, especially for both Ford and chevy to come up with it, decades apart, and yet use it nowhere else...? If Ford had made all the 390-427-428 engines with aluminum intakes, I could readily understand it, but they almost never- if ever- did that for production.....

[This message has been edited by cvxjet (edited 09-12-2015).]

quote Originally posted by Raydar: I know you said LT, but do you mean the upgraded LS structure? The latest LT1 and LT4 are essentially the LS architecture with direct injection and a few other "toys". This was not to argue. Just asking for clarification. Either way. I have wondered how that new 4.3 would fit in a Fiero, since the real constraint with the LS block seems to be room for belt driven accessories. The 4.3 would have to be at least 4 inches shorter than the LS, or one would suppose...

The new Gen V engines are are about as much an LS, as the LS is a Gen II SBC. Almost nothing is directly compatible between them.

Dobey is completely right....I just finally found some pics to compare + discriptions; I had no idea they had made that many changes to the engine design.....Yes, it is obviously a PR engine, and it is basically the same size, but just comparing the head pics, the intake and exhaust valves are reversed, the intake ports look like normal ports, rather than the high-narrow "slot" design that the LS used.....

There is not a huge bump in power, which led me to believe there wasn't that much differnce- but engine efficiency is pretty high, now, compared to when the LS came out in 97, so the bumps are going to be incremental....Of course, it's hard to directly compare MPG, because the LS rarely had DOD, while all the Lts have it.

As a side note here, I look at the LS V8s and see the performance/MPG beating most everything out there, yet the typical measure of efficiency is HP/L......But a 3L turning 6000rpm is PUMPING the same amount of air as a 6L turning 3000rpm....I read something somewhere- someone suggested this and I am not claiming credit here- Anyway, take the Liters and multiply it by the RPM the HP peak is at, then divide by the HP, giving you the amount of air pumped per minute to create that HP.....Of course, you should then divide that number in half, since a 4 stroke takes two revolutions to fire all cylinders.....Most engines fall between 38 and 42 L total air pumped per minute per HP created....This whole calculation goes out the window with Super or Turbocharging......

The best engine I've ever ran this calculation on was a 565 CI(9.26L) jet boat engine(Pro-stock heads, single 1250 carb, and very exotic cam design) creating 1000 hp at 6000 rpm; 27.8 L! And no, my boat engine doesn't do well on this scale....47L......Even tho I did get the quench measurement down to .040".....

quote Originally posted by cvxjet: Yes, basically it'sa rebop of the LS engines, but now designated as "LT", very much the same except a few improvements- The V8s get the DOD across the board- I don't know if they put that in the 4.3- seems like it would really shake with only 3 giant cylinders running- Yes, most assuredly that engine would be great in a Fiero- But it's not a winder, at all- I beleive it redlines at 5800- But it has a lot of oats- 280 or so HP....I was lookibg for a weight but couldn't find hide nor hair...and weight is a slippery number anyway; Short or long block, with top dressing, accessories, etc. Since it's only used in RWD, you will have to deal with the Starter location problem, tho...Hopefully there is room for mounting it on the left side.

I'm pretty sure the new Ecotec3 4.3 V6 uses the big RWD Chevy bell pattern, so you'd need to use Archie's LSx kit to mount it in a Fiero. With that, you should be able to use the same starter solution he has for the LSx V8s. The redline is about the same as the V8s. It does have AFM, as some of the High Value V6 engines did as well. The redline on these engines is set based on the power curve, and the mechanical limits of the components used, to minimize warranty claims, and to get the best emissions/economy balance, to meet federal regulations.

Well.....I hadn't actually taken the engines apart or anything.......

quote Originally posted by cvxjet: Dobey is completely right....I just finally found some pics to compare + discriptions; I had no idea they had made that many changes to the engine design.....Yes, it is obviously a PR engine, and it is basically the same size, but just comparing the head pics, the intake and exhaust valves are reversed, the intake ports look like normal ports, rather than the high-narrow "slot" design that the LS used..... ...

That's interesting. They look quite similar to me, externally.
But it is what it is, I suppose.

I've never taken them apart, either. (Well... other than taking the intake off my 5.3.)

And yeah... I would also expect the new 4.3 to use the modified SBC / LS tranny bolt pattern.