I have a thread this relates to
Turbo 3.4 DOHC Build w/aluminum rods


I’m still waiting for a response from the cat with the DOHC engine, I have sent him several E-mails on the subject with no response. I’m sure he still has it, he is just slow to respond.
While I have been waiting I have been drooling on some of you guys doing the G6 6 speed trans swap and am considering changing teams, looking around I see a lot of 3900 engines and 6 speed transmissions on the cheap 1000 $ and less for the pair, but I have some questions for you guys who have done a 3900 or 6 speed swap…. Maybe out there someone has done both and has some insight.

If you took the whole 3900 engine and transmission together and swapped it into a Fiero wouldn’t it be a relatively easy swap ??? No special clutch or fly wheel parts to match up.

How about the axle shafts would they need to be custom or can you come up with ones that will work mixing and matching stock pieces???

What needs to be modified to get the 3900 to fit in the cradle???

Does the alternator mount up high like the 3400 so there is a clearance problem with the trunk???

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Scoobysruvenge

Most likely some axle issues... using the 3900 PCM would most likely be tough. So, aside from finding, and tuning your own pcm for it (honestly wouldnt be that hard), and mounting it up, you would technically be done.

a 5speed 3800sc would be 3000x easier still, and make more power. A 3800 n/a would most likely make nearly as much as that (yes I know the rated power is higher.. but the curve is sorta trashy, and you most likely wont get the same power out of the weird ecu)

http://media.gm.com/us/powe...r%20eng%20trans.html

The G6 GXP powertrain is about halfway down the page. Click on the "P" link on that row and you can get a pic of the engine. The alternator is a high mount though.

I think the ECU is the biggest challenge on this swap. The LZ9 uses variable valve timing (cam phasing) to help it make that power. Either you would have to swap out the timing gear or keep an ECU that is compatible with the cam phaser.

Keep us posted if you go for this swap. I am planning to do this eventually on my car. Add a supercharger to the 3900 and it would blow the 3800 away for power not to mention the 3900 is lighter and doesn't take up as much space in the engine bay.

Joseph Upson has a 3900 twin turbo swap you should look into. It's basically the baseline for what i want done with my Fiero (after i finish my turbo audi project).

Forget the VVT except for simple on off function with limits for a much smaller angle of variation relative to stock. Otherwise simply sending the stock cam out for a regrind to get a little more performance and degreeing it in for proper fixed cam operation should be all it needs. Rather than make assessments relative to the 3800, I'll continue to be patient until I can return to finish mine and have it dynoed. My engine has run at both extremes, fully retarded cam and currently fully advanced which I'm sure has reduced the power output by at least 50 hp or more compared to what it would produce with the cam dialed in according to the regrind specs. The cam is advanced by more than 15 deg so were it not for the turbos it probably wouldn't feel very impressive at all. Just wish I had thought a bit more about the cam dynamics from the start. I hope to have a built and stroked version by Feb of next year with a small range of VVT function ~5 degrees + and -- of install angle. Sleeves are available for the smaller cam bearings that support the earlier camshafts or you can have Delta Cams resize the journals on the earlier cams to fit properly, just make sure the first journal is square to fully cover the additional or repositioned oil hole in the front cam bearing.

Stop being a Fiero owner and spend the $500 on HP Tuners to modify the G6 ECM.

quote Originally posted by Will: Stop being a Fiero owner and spend the $500 on HP Tuners to modify the G6 ECM.

If it were that simple Will I would but currently there are no provisions for boost and at the moment I have no time to finish the project let alone secure the number of hours necessary to modify and install an G6 accelerator pedal, steering column and dash that would likely be necessary, when Code59 is so much more practical now that it's working with DIS.

quote e no provisions for boost and at the moment

Its not a maf car?

and will, I do believe that there are still passkey/vats issues even with HPT.

It is my understanding that the 3900 comes in two flavors one with VVT and one without, not that I am against using the VVT if I can get it to work.
The 3900 also has oil injection on each cylinder and from what I read a much better oiling system in general over any of the previous generations or the 3800 engine platform.
Don’t get me wrong the merits of the 3800 engine platform are well documented in these pages, but it is not out of the box enough for me.
As far as the fuel system goes I still plan to do the mega squirt thing, one of the programmable ports could be configured to operate the VVT if it is as simple as the way Joe describes it here in this thread, although I know very little about the subject I am sure with some homework it can be done.
For 500$ I can buy all the Megasquirt components I need plus some extras, now I know some of you dislike the hated Megasquirt, but I am watching it work on my brothers Turbo 6 mustang, he just put a new engine in it and we had it started and idling in an hour on the base Map, we took it for a spin around the neighborhood and dialed it in further for about two hours, it is now ready for the dyno.
My brother called around to see who had some dyno experience with MS. and found AED who said that a MS. Rep comes there every month or so (from Maryland) and gave my brother the Reps number. After speaking with him, he said that he would be interested in helping out with the tune next month free of charge. The only cost would be the 80$ and hour AED charges to use the dyno and it should at most take four hours to tune it up.
How’s that for support!!!

I will be reading up on Joes post as well as others on the subject of the 3900/6 speed swap.

Thanks for all of your interest.

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Scoobysruvenge

quote Originally posted by Scoobysruvenge: It is my understanding that the 3900 comes in two flavors one with VVT and one without, not that I am against using the VVT if I can get it to work. The 3900 also has oil injection on each cylinder and from what I read a much better oiling system in general over any of the previous generations or the 3800 engine platform. Don’t get me wrong the merits of the 3800 engine platform are well documented in these pages, but it is not out of the box enough for me. As far as the fuel system goes I still plan to do the mega squirt thing, one of the programmable ports could be configured to operate the VVT if it is as simple as the way Joe describes it here in this thread, although I know very little about the subject I am sure with some homework it can be done. For 500$ I can buy all the Megasquirt components I need plus some extras, now I know some of you dislike the hated Megasquirt, but I am watching it work on my brothers Turbo 6 mustang, he just put a new engine in it and we had it started and idling in an hour on the base Map, we took it for a spin around the neighborhood and dialed it in further for about two hours, it is now ready for the dyno. My brother called around to see who had some dyno experience with MS. and found AED who said that a MS. Rep comes there every month or so (from Maryland) and gave my brother the Reps number. After speaking with him, he said that he would be interested in helping out with the tune next month free of charge. The only cost would be the 80$ and hour AED charges to use the dyno and it should at most take four hours to tune it up. How’s that for support!!! I will be reading up on Joes post as well as others on the subject of the 3900/6 speed swap. Thanks for all of your interest.

No non VVT 3900 exists to my knowledge, you must be refering to the 3500. VVT is simple as far as on off usage but it must be limited to a smaller sweep area under those circumstances (non VVT PCM use).

My first instinct is to trash the upper intake and throttle body and substitute them with a hand made sheet metal upper intake and cable operated throttle body. Do away with the VVT and fly by wire altogether.
Joe can you elaborate on what you would do different with the cam, and you are correct after some research the 3900 comes as a VVT engine only.
To me eliminating the stock ECU and using something aftermarket to deliver the fuel is a must if you plan to turbo charge the engine and make no mistake I do plan to use a turbo or two.
I like the twin turbo set up Joe is running in his build and would like to do the same with my project. There are some serious advantages to running a two turbo setup on a V type engine that displaces 4.0 liters or more according to Corky Bell.
Joe would know better than I about the exhaust routing, but it seems to me that two 1 ½ pipes would be easier to route in the tight confines of the Fiero engine bay than a single 3 inch exhaust would be.
Anyway just a few things I am thinking about as I contemplate another change in strategy, good thing I haven’t spent allot on my engine components yet.

Goods things come to those who wait…

Haste makes waste…

And so on………

look up WOT tech, they offer billet 65mm TB's for the 60degree's, or adapter plates to use other TB's, also cary cams, etc.
as for the 3900 ecu, its un-usable, i dont think anyone has cracked the security onthem yet.

quote Originally posted by Scoobysruvenge: My first instinct is to trash the upper intake and throttle body and substitute them with a hand made sheet metal upper intake and cable operated throttle body. Do away with the VVT and fly by wire altogether. Joe can you elaborate on what you would do different with the cam, and you are correct after some research the 3900 comes as a VVT engine only. To me eliminating the stock ECU and using something aftermarket to deliver the fuel is a must if you plan to turbo charge the engine and make no mistake I do plan to use a turbo or two. I like the twin turbo set up Joe is running in his build and would like to do the same with my project. There are some serious advantages to running a two turbo setup on a V type engine that displaces 4.0 liters or more according to Corky Bell. Joe would know better than I about the exhaust routing, but it seems to me that two 1 ½ pipes would be easier to route in the tight confines of the Fiero engine bay than a single 3 inch exhaust would be. Anyway just a few things I am thinking about as I contemplate another change in strategy, good thing I haven’t spent allot on my engine components yet. Goods things come to those who wait… Haste makes waste… And so on………

In addition to having a unique design for VVT, the 3900 cam has much larger cam lobes than the non VVT cams and although stock duration is said to be about 197 deg no one to my knowledge has measured how much area is under the curve for that duration in terms of leading and trailing edge ramps. That's why I'm opposed to converting to the non VVT camshaft. The VVT camshaft is also designed LSA wise to operate properly for advance and retard, for example if I retard my reground cam (with changed LSA) beyond 0 deg in desktop dyno the power curve is a wreck and the torque drops off drastically, however it does produce more power than stock in the full advance position. When the stock cam settings are entered and it is retarded power climbs from 10 deg advanced all the way through to -15 deg retarded.

With that said, since GM had a working 270 hp HO example at 06 SEMA with a mild work over including a different cam, I believe the best route to take is a simple regrind of the stock cam to add more duration and lift to an already 240 hp camshaft and either degree it in straight up with simple rigid blocks of aluminum in the VVT module, or use blockers that just limit the camshaft retard from the proper install degree angle for the regrind to a few -deg.

The reason the advance and retard needs to be limited is because some of that function serves the purpose of EGR and may not be beneficial at either extreme. Fully retarded all the time = terrible fuel economy, even sitting in the driveway revving the motor you can nearly watch the needle drop. Full advance provides great fuel economy but a drastic reduction in power. Desktop Dyno estimates intersection of the power curves between full advance and full retard (point where power drops off in one and picks up in the other) to be about 3500 rpm so anything below that the cam should be at optimum install degree angle or a little advanced and then retarded above that rpm. Since the transition is quick there should be no problem tuning for it with one fuel table since the cam would retard in a split second to the opposite extreme instead of a continual variable state that only the VVT PCM can adjust to.

Everything you need to adapt this engine to traditional connectivity can be found on the 60 degree forum. I use a Northstar Throttlebody with the adaptor. There is also a non variable intake for this engine as well although I doubt it matters under boost.

The other plus for this motor is that my LS1 forged pistons are the same bore as stock and cost me less than half of what a custom set would and they came complete with rings, locks and pins. The 2.25" crank pins are destined to be offset ground to ~3.435 stroke for chevy 283 connecting rods. All of the new components are considerably lighter than stock. There's a lot of potential in this engine and someone between me and the other two individuals that have working 3900s will be able to demonstrate it without question.

Westbenddynotuningllc.com can make you a chip for the fully advanced position. I would think it would be a good starting point even after adjusting cam timing.

Joe,

I know this is unrelated to the 3900 but what can you tell me about the 3500 LX9 7484 crank casting?? is it forged if so it could be used in any 3100/3400 engine???

Is it true ??? Did GM mass produce a forged steel crank for the 3x00 engine ???
I stumbled into this doing some research on the 3900 engine. It seems that some people out there are claiming that the LX9 sports a forged steel crank with a casting number of 7484. Below is one of the web pages I found some of this information on along with the claim of forging.

http://www.v6z24.com/registry/SuperDave

3500 LX9 is listed as having….
Forged steel crank 7484 casting
Stock forged steel rods
9.8:1 SCR stock pistons (Nice ratio for a turbo engine and are probably turbo friendly hypereutectic material)

If this is true these cranks could support the high horsepower that so many of us desire.
I see Joe Upson has a couple of these engines and seems to know something about these cranks.

I have a 3900 thread going where he has posted before, I will ask what he knows.
If any one has info on this let me know.

quote Originally posted by Scoobysruvenge: Joe, I know this is unrelated to the 3900 but what can you tell me about the 3500 LX9 7484 crank casting?? is it forged if so it could be used in any 3100/3400 engine??? Is it true ??? Did GM mass produce a forged steel crank for the 3x00 engine ??? I stumbled into this doing some research on the 3900 engine. It seems that some people out there are claiming that the LX9 sports a forged steel crank with a casting number of 7484. Below is one of the web pages I found some of this information on along with the claim of forging. http://www.v6z24.com/registry/SuperDave 3500 LX9 is listed as having…. Forged steel crank 7484 casting Stock forged steel rods 9.8:1 SCR stock pistons (Nice ratio for a turbo engine and are probably turbo friendly hypereutectic material) If this is true these cranks could support the high horsepower that so many of us desire. I see Joe Upson has a couple of these engines and seems to know something about these cranks. I have a 3900 thread going where he has posted before, I will ask what he knows. If any one has info on this let me know.

Yes, I sorted that out some time ago on the 60 degree V6 forum after mentioning that my 3500 crankshaft looked funny (forged) and was told GM only put forged steel cranks in 3900 V6 engines found in one or two SUVs, only to discover that I was correct when I checked with GM parts direct and found two crank part numbers that had shipping weights that differed by a few lbs, the heavier sporting the last four digits 7484 which I found on the crank snout of both my 3500 engines. Fortunately the cast iron version is the rarer crank.

The crankshaft to my knowledge has never been a problem so it's probably more overkill than benefit. The 2.25" crank pins however leave room for stroke increase when offset ground which I plan to have done.

All of the V6 rods are forged to my knowledge however the newer rods are powder metal forgings with cracked cap technology and yes despite the high static compression the engine is pretty detonation resistant, so far 7 psi, midgrade fuel and 212 deg inlet temps without a problem for one example before the intercooler install.


The VVT 3500 has a 3" stroke crank so be aware of that, the non VVT 3500 uses the same crank as the 3900 except for maybe the trigger ring.


https://www.fiero.nl/forum/A...090219-2-073962.html

[This message has been edited by Joseph Upson (edited 10-13-2009).]