new 3900?

[MidnightriderZ24]

im a tech at a gm dealer and i was doin a PDI on an 09 buick lucerne, and i noticed it was a 3900 and i popped the hood to check the essentials, and it had a different intake manifold on it and the timing cover was different as well as the accy mounting. anyone else see this version?

[bszopi]

That looks like the 3500VVT, not the 3900VVT. Looking at the Powertrain site doesn't really help either (http://media.gm.com/us/powertrain/en...2009/09car.htm) as all the photo have the plastic engine covers.

[MidnightriderZ24]

it looks like the 3500, but its not. i took the cover off since it had the different looking plenum. the placard also said 3.9

[IsaacHayes]

De-tuned 3900? Non VI?

[CNCguy]

When looking at pics of all the new 3.9s, it appears as though they no longer use the variable intake. The variable intake was wider and projected over the valve covers. The new plenum does look exactly like the 3500 VVT plenum that I have here.

The horsepower ratings have also dropped compared to earlier models (219~233hp vs. 240~242hp).

[Joseph Upson]

What's different about the timing cover?

Externally the intake manifold plenum is or was the only way you could tell for sure the difference between the VVT 3500 and 3900 aside from a snap on cover because everything else except what was needed to accomodate the shorter stroke internally is the same.

I wonder what prompted the change, the 3.6L maybe? From a cost effective stand point although it's more expensive overall to manufacture, it does see more vehicle applications with 19 listed as standard equipment across 09 car and truck applications combined, to only 4 for the 3900 and that's not counting the projected F-body applications or the Saab 2.8L application which is basically the same engine with smaller displacement that originated in the cadillac CTS models the 3.6L is now the only V6 option for.

I suspect the 3900 is heading the direction of the 3800. I made a similar comment about the 3800 back when the 3900 appeared and turned out to be right. Finances make the rules. Looks like we've got a steep learning curve ahead.

[IsaacHayes]

So the VI model is no longer available? That blows, less power booo!

Too bad GM seems to be doing away with their pushrods. Just when they were getting them very powerful. DOHC's are just too freaking big and heavy.

They should make a high revving 3.0-3.1 destroked LX9 with a turbo. That'd get good mileage, be small, and powerful. But that'd be too cool though..

[Joseph Upson]

So the VI model is no longer available? That blows, less power booo!

Too bad GM seems to be doing away with their pushrods. Just when they were getting them very powerful. DOHC's are just too freaking big and heavy.

They should make a high revving 3.0-3.1 destroked LX9 with a turbo. That'd get good mileage, be small, and powerful. But that'd be too cool though..

The 3.6L is only a little heavier than the pushrod motors, because it has an aluminum block unlike the 3.4 DOHC motor.

[gectek]

That is the 3.9 that is offered in the impala as well, it has the DOD on it as well as some of them are flex fuel as well...that is why they show less power, they detune them and run dod on them...the upper intake can still be had...but i dont think they even put them in anything but the G6 and the malibu anyway...

[Nightingale]

So is this model still VVT? I am assuming yes, but it'd certainly make swaps easier for those not wanting to mess with the vvt or disabling it.

[gectek]

yes all of them now are vvt...