Ironhead-tuner wanted

[Montanamotor]

Hi, folks.

Just to complete my questions regarding the Pontiac Fiero (see the DOHC-thread), I also want to ask you a questions or two about the tuning of two-valve iron heads.

How many HP are REASONABLY to expect from a naturally aspired, street/track-tuned 3.4 L stroker Fiero-engine?

My way, to achieve my ultimate goal, would be going to http://www.engine-parts.com/ for their 3.4 L stroker engine, have it tuned and ported in-house, and have it equipped with a MECHANICAL Rotrex-supercharger http://www.rotrex.com/

Due to local legal necessities, it ought to be an all EFI, all the time, fully street-legal engine (californian style). Therefore, I am even willing to invest in a modern, state-of-the-art EFI system to achieve that.

My question: How many HP will a well-tuned 3.4 L stroker be able put out while NATURALLY aspired, and in which configuration?

I need these data to make the best choice for the Rotrex-blower.

Important note: I give a damn about a smooth idle. What I want, instead, is mid-range and top-end power, to chase Porsches over small country-roads. Torque will be delivered by the Rotrex-blower, anyway. But what I need is a much higher rev-limit than stock, to achieve my goal. 6000 rpm is a must. And if I can get 300 HP from a blown iron head, so be it!

Why? That's why: A 300 HP 3.4-Fiero should reach a Vmax close to 165 mph, versus the stock 124 mph at 4500 rpm with the nimble 139 HP 2.8 L-engine.

But only if a tuned iron head will deliver it's max HP at 6000 rpm, instead of at 4500 rpm, the stock gearing will be just fine to go 165 mph.

Ifthat's not feasible, and the max rpm would stick close to the stock 4500 rpm for max HP, The car would need a diff with a 25 % lower gearing, to achieve 165 mph at 4500 rpm.

On the other hand, if a tuned iron head will deliver it's max HP at 6000 rpm instead of at 4500 rpm, the stock gearing would be just fine to go 165 mph.

Wnat do you think? Are there any other trustworthy tuners out there who could help me with a serious 300 HP-ironhead-tuning including supercharging and EFI - or are my ideas completely over the top?

Your thoughts?

[trotterlg]

You will be hard pressed to get any kind of power out of an iron head engine past 4,500 rpm no matter what you do to it. Iron heads just plain suck. It has been shown many times that the best ported iron heads are still much inferior to stock aluminum heads. Larry

[pocket-rocket]

You should consider a 3500 LX9. Superdave got ~275hp to the wheels with porting, a cam, long tube headers and a tune. The only reason he failed to get his Z24 into the 11's was because with the torque it had he couldn't get enough traction off the line.

I would have suggested a 3900 as well, but the VVT is hard to get around and since TCE isn't producing products right now you can't get the cam spacers to put a normal cam in it.

Or boost a DOHC in it :-)

Sent from my HTC One X using Tapatalk

[Montanamotor]

Your advise seems more than fair, Pocket-Rocket.

In a dutch Fiero-forum http://www.fiero.nl/forum/Forum2/HTML/127251.html , I found a thread regarding swapping a 3500 LX9 for the humble fiero 2.8 L iron head. This american guy - from Charlotte AL, bought the 3500 LX9-engine from a scrap-yard with 19k miles for $300 !!!! Jeebus!

I think that's the way to go.

[Montanamotor]

trotterlg,

I see your point. On the other hand, other pushrod-engines like Chevrolets LTD inline-six will gladly rev up to 7500 rpm, when equipped with appropriate valves, springs, rockers and pushrods. So yes, until proven impossible, Iwould still consider an iron head to be able to be revved up to 6000 rpm under load - especially so, if equipped with some kind of boost, like the rotrex-guys http://rotrex.com/Home offer.

[geoffinbc]

Although Iron heads are out flowed by the aluminum heads they can be made to rev to 6000rpm or even 7000rpm. Don't forget that years before the aluminum heads were introduced people were racing with the 2.8L iron head motor in circle track and miget. A blower will only help the engine breathe in the top end. It is of course not the optimum combination for all out power but everyone has their reasons. FYI that ARI stroker kit is junk and is just a combination of stock and aftermarket replacement parts. You can make it yourself with a 3.1L crank and some replacement 3.1L pistons from CP. You cannot make a 2.8L/3.1L block into a 3.4L there is not enough cylinder wall thickness to make it happen.

So let us know if your keeping iron heads or making the switch to aluminum and then we can offer specific information.

[Superdave]

you can rev an iron head to 6K all you want but it won't make useable power up there. The amount of cam it would take to make it worth while N/A would make it a race-only application.

Curtis ran his up to 8K with a solid roller cam and like 18 PSI on a completely forged bottom end. Guys with mostly stock 3x00's and lower boost are running faster times these days and daily drive the cars.

[Guest]

Iron heads, if properly ported, as well as a good valve job, can still make power at 6000 rpm with the right cam selection. Most cams you can buy are designed for lower rpm peak power, but you can still find cams designed for peak power to be closer to 6k rpm instead of 4500 rpm. The heads if ported well will support that cam too.

Questions. Are you starting with a 3.1 block or a 3.4 block? A 3.1 block won't be able to be bored out to a 3.4 as someone else has mentioned. So I would start with a 3.4 block, or even better yet, a 3400 block. That is a 3.4 block factory equipped with aluminum heads, but its better because it came with a roller cam.

Using a 3400 block you just put in iron head pistons and WOT here sells larger roller cams. If you stick to the 3.4 block, technically you can still use a roller cam, but it does not have priority main feed so you might not be able to use a hyd roller camshaft, and have to use a mechanical roller cam instead, which are getting harder to find but not impossible

A 3.4 engine, with ported heads, a proper flat tappet cam with about .450-.480 lift, and the proper intake manifold porting as well as free flowing exhaust can get you to 200 hp N/A at the crank, and maybe a tad bit more like 220hp. There was a member on here selling an iron head ITB intake manifold for the iron heads. That intake, with ported heads and the right cam will make 220-240 crank hp in my opinion with a good tune and still be EFI. Then adding a rotrex will be simple, but you would have to build a box for the ITB intake to allow pressurized air from the rotrex.

The iron heads won't make as much power as the aluminum heads, but they can still easily get you to your goal of 300hp with the rotrex.

[caffeine]

Ya 300 hp is doable with iron heads but you could probably make 300 hp with aluminum heads and like 5-6 psi boost. Probably even with the stock cam.

[ericjon262]

Due to local legal necessities, it ought to be an all EFI, all the time, fully street-legal engine (californian style). Therefore, I am even willing to invest in a modern, state-of-the-art EFI system to achieve that.

this is the only thing that may give you problems. how are they there about engine swaps? there's all kinds of stupid rules about engine swaps in california.