Real Fiero Tech

Why a 3900 and iron heads might not work, and be anti productive pending on your priorities.

http://www.fiero.com/forum/Archives/Arch ... 0.html#p15

You could def fit some larger valves in the iron heads though. Joseph says the 3900 valves are 1.87/1.52

bleh, fiero heads on a 34/3500 is bad enough in my book, but a 3900...

Shaun41178(2) wrote:Why a 3900 and iron heads might not work, and be anti productive pending on your priorities.

http://www.fiero.com/forum/Archives/Arch ... 0.html#p15

You could def fit some larger valves in the iron heads though. Joseph says the 3900 valves are 1.87/1.52

Interesting photos. Thanks for posting.

I'd have to look at it myself, and maybe even compare the 3900 and 2.8 side-by-side, but it looks like it would work.

As noted, it would seriously compromise the power of the 3900, but it's also the way to make the most of the iron heads.

Correct, it wouldn't be the best decision, but if you wanted the most displacement, and still use the iron heads it would probably work. Some modifications to the combustion chambers, and some larger valves would help.

It would be like putting a TPI intake from a 305, onto a 383. Lots of low end torque but no top end. If your goal is more torque over a 2.8 or a 3.4 than yea, understandable.

Curious as to how a fully ported set of iron heads with an itb intake would do on otherwise a relatively stock 3900, factory pistons and all. CR would be low but I don't know those exact specs at this time.

Even so Joseph upsen did a offset crank with ls1 pistons and with the aluminum heads he said he had like 11.X:1 compression. i have found that usually you get a full 2 points drop with the iron heads when comparing to gen 2 and 3400 heads. Not sure what the CC of the 3900 head is, but even a 2 point drop would put you around 9:1 or more which isn't awefull.

Just imagine that tq monster with a fiero intake and a pair of tiny turbos or a single small turbo. 400 lb ft and 230 hp. LOL

With the LS1 pistons available, you should be able to get any CR you want with shelf parts.

It appears this link shows a better shot of the heads and if you look closely it appears that you can see the cnc marks in the port entry

http://ncfiero.com/Forum/viewtopic.php?f=9&t=18

Interesting, but the photo still looks odd... like the ports were media blasted after being machined, or were incompletely machined and some original as-cast surface remains.

Also, the vane has been removed. Horrors.

falconer heads don't have the vane either. Either way it appears this guy has a 2.8 that makes 170 whp. Now is it with the cnc'd heads? I don't know but I will guess yes to that.

I got a response and he is going to look for his flow sheets.

I always judge a port by feel rather then looks, but even still, those ports don't look all that great to me. maybe it's the lighting, but it looks like there is a big dip in the floor.

Edit:

after looking again, I realize the lighting was playing a trick on me, still though, the don't look all the impressive to me.

Here you go:
@ 28 inH2o
Intake
200=59
300=113
400=173
500=182

Exhaust
200=37
300=132
400=130
500=133

These are the numbers of the heads. Not sure the bore of the test not how many angles on the valves

Shaun41178(2) wrote:
Curious as to how a fully ported set of iron heads with an itb intake would do on otherwise a relatively stock 3900, factory pistons and all. CR would be low but I don't know those exact specs at this time.

I was able to find out some specs on a 3900 as far as the Combustion chamber volume of a 3900 head and it comes in at about 36.5cc's Swapping to a fiero which is roughly 52 will bring compression down to about 8.1:1

I guess there is a cometic head gasket that is thinner that can bump it up closer to 8.5:1

info taken from here
http://60degreev6.com/forum/showthread. ... 3900+heads

Figured I would post a mock up pic. Still a long ways to go.

where do you keep finding this shit?

My question isn't so much as where, it's why? Just swap a 3800 already.

Aaron wrote:My question isn't so much as where, it's why? Just swap a 3800 already.

This build actually interests me more now.. If it's possible to make a decent amount of power with a 2.8 or similar, it might be more feasible to make a Fiero competitive in motorsports. The engine swaps are what make it hard to be competitive, because they result in an automatic bump to a class with a much higher level of preparation, where the Fiero suffers in other aspects.

That's a good point, I hadn't thought about that. But what a terrible starting point for horsepower/pound. But I guess anything more is a step up, but I don't see it ever getting above 200 without boost.

THE PUNISHER wrote:where do you keep finding this shit?

If I was in the position I am now financially years ago, I would have kept those prototype gen 1 aluminum heads you picked up and used them on this build. I have been getting a lot of overtime at the taco bell drive through this year.

I have been playing with aluminum heads for so long, picking those cast iron pigs up for the mock up, made me remember why I wanted to ditch them in the first place.

Even if this engine only makes 200 crank, its the same as a series 2 3800n/a. Why would I go through the trouble of swapping a motor, new engine mounts, wiring, computer, just to have the same hp as what I can make with this? Now granted, this will make more than 200 crank. Once the build starts moving along faster, there will be a thread in advanced tech showing how its going to get 350+ hp without boost. I know, sounds like BS doesn't it?

Out of 2.8l with 2 valve heads n/a? 350 my ass Shaun, get real.

And although a 3800 makes 200 stock, it has a bit of an aftermarket. Just a little.

Aaron wrote:Out of 2.8l with 2 valve heads n/a? 350 my ass Shaun, get real.

And although a 3800 makes 200 stock, it has a bit of an aftermarket. Just a little.

I don't think Shaun is using a 2.8L block.

I think I read 3900 in this thread. I guess with 3.9l it's possible, but that's just about maxed out in every way.