Opinions needed

jene · Post by **jene** » Fri Feb 29, 2008 1:27 am

Engine swap number 2 might be closer then planned. I was just curious about what you guys thought about a 3900 Has it been done yet? Would i need to change alot of the wireing, computer...ect? What about mounts? Or should i just swap in another 3400 and call it a day?

fastlane02 · Post by **fastlane02** » Fri Feb 29, 2008 2:11 am

mmmm i'll have to do more research on this. someone need to see what the diff is in the motors

speedygtz · Post by **speedygtz** » Fri Feb 29, 2008 10:00 pm

whats wrong with your litter 3400sfi, and i say hell yea, but you might want an upgrade on teh trans, i dont know much about the 3900, but im sure by the sounds of it, it would tear that trany to shreads....

JeffD · Post by **JeffD** » Thu Mar 06, 2008 4:23 pm

that engine is VVT, you definitely will need a different computer! I know that some people @ 60degreev6.com have gone over this engine, you might want to check over there.

Mr. Beefy · Post by **Mr. Beefy** » Thu Mar 06, 2008 4:55 pm

I know that Eric was toying with that when he had the Z. Who knows....

wicked-irocz · Post by **wicked-irocz** » Mon Mar 17, 2008 8:23 pm

there was supposidly one that wasnt VVT. I remember canada talking about it over on bstuff. Him, buls, and eric were discussing it.

Post by **Cliff8928** » Tue Mar 18, 2008 2:40 am

I believe all the 3900s are VVT. Some are DOD, but not all.

JeffD · Post by **JeffD** » Sun Mar 23, 2008 2:51 pm

Maybe you could replace the timing chain and sprockets with 3500 stuff, but you probably would have to swap the cam too.

IsaacHayes · Post by **IsaacHayes** » Sun Mar 23, 2008 10:41 pm

60degreev6 is the place to discuss this.

But I'll help you out.

All 3900 were VVT. Some DoD and some Flex fuel. Getting the plain VVT 3900 of course is the way to go.

3900 and the 3500 VVT are related, but NOT the LX9 non-vvt. The VVT motors are not compatible with anything from the 3400/3100/3500-non-VVT.

You'll need to lock the cam phaser with a pin, and have the cam re-ground for normal use. There is a guy who has a 3900 Twin-Turbo in his Fiero and did that. For the variable intake, you can run the 3500 VVT upper, or figure out a way with window switches to activate the 3900 intake.

The cam cover might need modifying to clear the frame rails, or cut and box the frame rails, since it sticks out for the cam phaser. TCE motorsports (makes some of the stuff at the WOT-TECH/60degree store) is working on a kit to remove the cam phaser stuff.

Mounts, there is one version that has a mount on the timing cover that probably can be adapted to use the stock passenger mount. Others I don't know off hand.

Cooling hoses might need to be custom as it uses a new route and doesn't push coolant through the intake manifold (hurray no more leak issues), but thats a no-brainer.

Of course you'll need an external trigger, WOT-TECH sells that as well as a TB adapter so you can slap on a northstar TB since the factory engine uses an electronic one.

Exhaust would be custom (flanges at WOTTECH) or use the 3900 manifolds which are tuned sorta, (not logs) as they are not the same bolt pattern as on the heads as the older motors.

You'll need to be able to tune, OBDII swap if need be.

But yeah that's about it. I wouldn't try to use the 3900 ECM as that would require a ton of wiring, BCM (body control module) and I dont know if you could tune it to work with the 46t0-e... Loosing VVT and Varible Intake is not that big of a deal since you'd have the cam re-ground to something hot anyways since you'd have to have it ground, and the variable intake could be made to work with window rpm switches or use the 3500 vvt one.

AFAIK, the vvt 3500 and vvt 3900 are similar in that they share the same block and heads, the 3900 is just stroked out more and had a variable upper intake manifold,

IsaacHayes · Post by **IsaacHayes** » Sun Mar 23, 2008 10:44 pm

So if you feel like doing some work, it would be a bad-*** engine.

Or if you want to be better than just a 3400, get the NON-vvt 3500 (LX9) and an external crank sensor and bolt that sucker in. Re-ground cam if you wish, and whatever other goodies. 200+ HP is nice.

There is a 95 corsica that just swapped in a 3500 LX9 with 3800 injectors and 3400 TB, and he says 1/4 throttle makes the tires light up with ease. Now he has done an OBDII swap by just re-pinning the ECM connector (no wiring harness swaps!!!) and is using a 97 transport ECM and has it running and is finishing that up now and will soon be getting a DHP or HPT to tune it. He lives a little over an hour from me so I'll be checking it out sometime soon once he gets it going a little better!

Asylum · Post by **Asylum** » Mon Mar 24, 2008 10:02 am

I looked long and hard at the 3900 a year or so ago, with no concern over cost, and still decided it just wasn't worth it at the time.

I'm still convinced a 3500 is still the most bang for the buck in our cars, by a long shot.

Kyle Anderson · Post by **Kyle Anderson** » Mon Mar 24, 2008 5:53 pm

(IsaacHayes @ Mar. 23 2008,21:44)QUOTEThere is a 95 corsica that just swapped in a 3500 LX9 with 3800 injectors and 3400 TB, and he says 1/4 throttle makes the tires light up with ease. Now he has done an OBDII swap by just re-pinning the ECM connector (no wiring harness swaps!!!) and is using a 97 transport ECM and has it running and is finishing that up now and will soon be getting a DHP or HPT to tune it. He lives a little over an hour from me so I'll be checking it out sometime soon once he gets it going a little better!
I'm extremely interested in this!

I've already rewired an OBD2 harness for my car, but I got lazy with the project after the death of DHP.. I'm sure I can still find one, but ongoing support would be nice.

I would love you if you got more info about this guy's swap, and whether or not HPT can be made to work.

To add to Jene's question, I'm convinced that 3500 is the best option we currently have. There's not that much more work to swap one in compared to the 3400. From what I gathered just looking around 60degreev6, 3900 is considerably more work, but the power gains are worth it if you have the means to get the swap done.

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