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3900 V6 Engines, Let's Talk About Them...


3pt1lumina
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Okay, so my next vehicle will be an Impala LT or LTZ with a 3900 engine. I know absolutely nothing about these engines. I searched but can't seem to find one, but if there's a thread already, lock this and point me in that direction, but if not, let's talk about them here.

 

I'm curious to know more than anything about reliability. If I plan to buy a vehicle with this engine, is it going to be like a 3x00 and require LIM's all the time, or like the 3500's that always have failing head gaskets?

 

Also, performance wise being stock how are they, and what can be done to them to boost performance?

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Carbed 2.8 ---> [2.8 & 3.1] ---> [3100 & 3400] ----> [3500 & 3900]

 

LIMGs aren't so much an issue because coolant no longer flows through them. Head gaskets shouldn't be an issue, they fixed that issue early. The problem is with the crossover leaking coolant. Not a terrible job on the 3500, should be about the same on the 3900 I'd imagine.

 

 

"It produces 240 hp and 240 ft·lbf torque, with a wide torque curve. 90% of the torque is available from 1500 rpm to 5500 rpm"

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The 3900 has continuously variable valve timing, variable intake timing, displacement on demand. It makes the same horsepower as a L67 but does it N/A. There are not a whole lot of modded 3900s because they're still relatively new. But there are some:

This is Joseph Upson's 3900 on 60* I believe this is in a Fiero.

[ATTACH=CONFIG]3233[/ATTACH]

 

As far as reliability, nothing yet. So far they are not failing yet, but it usually takes a couple of years before nasty gremlins start to show their face.

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Good to know that. What's good is I am not planning on buying an Impala right away, so I have time to learn about this engine a bit. And if there is any issues that come up as gremlins I can see what they are between now and then, whenever then may be:lol:

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Good to know Buck...my mom's old 07 Impala LS did about the same before she turned it in, it had the 3500 as well.

 

My future sister-in-law has an 3900 06 Impala LT with 55k on it and she beats the crap out of it so I can't figure out what it gets for gas mileage... but it's been holding up well for her so far.

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The 3500 in my Monte gets about 27 on the highway as well, at 70-75mph (it's got 110k miles on it now)... So far the only issue I've had with it in almost 15k of ownership is a very slow external coolant leak from either the crossover or the head gasket... It's only about a half gallon a year, so I'm not super concerned with it yet...

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The headgasket issue on the 3500 is so overrated:lol:

 

Lemme put it this way, it will be uber rare for the headgasket to leak so much it will actually pose an issue. The most I have seen is them leak so bad that you have to add roughly 1 gallon worth of coolant every year. Typically 1/2 gallon once, the 1/2 gallon 6 months later.

 

Having friends at GM dealers who loved doing these under warrenty are now sad. Roughly 6 months ago GM told all dealers to NOT WARRENTY the headgaskets unless the customer was complaining like hell and that the coolant loss was quite severe. Prior to that, there were getting headgasket jobs off of cars that were coming in for just oil changes. They would tell the customers they are leaking and are under warrenty and it would be repaired. The customer would be oblivious to the fact they were leaking.

 

One point to make, i have never seen or heard of a single one causing an internal leak failure. Every leak I have seen or heard about was purely external.

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My parents have an 07 Impala LTZ with the 3900 in it. They came from an 03 Impala LS with the 3800. To them, the gas mileage sucks. The 03 got much better mileage. I believe they are getting around 20-24 in town and 27 highway in the 07. Power wise, I have driven it a couple times, and it's not bad. Not the push you in the seat of the L67, but has good pickup.

 

If you are looking for mileage, I think the 3500 is the one for that. I know my fiance's G6 gets 24 around town and close to 30 highway between Binghamton and rochester. Stay away from the 3.6L with mileage. It's similar to the 3900, but I am only getting 20-22 regularly, and 25-27 highway. Sucks, cause I came from an integra that got 29 city, 35 highway.

 

Overall reliability of the motors isn't bad. My parents bought their new, and I think the steering shaft issue is the only one they've had real issues with (very common issue in most newer GM cars)

 

Overall, the 07 Impala is a nice car and my parents are happy with it.

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The 3500 in my Monte gets about 27 on the highway as well, at 70-75mph (it's got 110k miles on it now)...

 

See- I would have thought the last of the Monte's with the 3500 would fair better in the MPG than the Impala due to it being lighter....

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See- I would have thought the last of the Monte's with the 3500 would fair better in the MPG than the Impala due to it being lighter....

 

Like I said, my mom gets 30-31 at a surprising average speed of 80-85, in her 2006 monte with 3500

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I've had to replace a couple leaking water pumps on 3900's. It's a dead easy job. I've personally never seen one with the head gasket leak or crossover leak, so I'm with Bob and don't think it's a real big concern. My mom has a 2006 Impala 3LT with the 3900. Has 60k, no engine trouble yet. I really like it. It has plenty of power no matter where you're at in the powerband. 2006 models have an active intake manifold, 2007 newer do not and the 2006's make 11 more hp because of it. 2007 and newer models have displacement on demand and thus have higher fuel economy ratings than 2006's.

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I've had to replace a couple leaking water pumps on 3900's. It's a dead easy job. I've personally never seen one with the head gasket leak or crossover leak, so I'm with Bob and don't think it's a real big concern. My mom has a 2006 Impala 3LT with the 3900. Has 60k, no engine trouble yet. I really like it. It has plenty of power no matter where you're at in the powerband. 2006 models have an active intake manifold, 2007 newer do not and the 2006's make 11 more hp because of it. 2007 and newer models have displacement on demand and thus have higher fuel economy ratings than 2006's.

 

What's your MPG's city/highway with it?

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What's your MPG's city/highway with it?

 

Sorry I don't have any real good info on that. I've driven it many times times and am impressed with the car, but I've never spent any period of time with it to have checked mileage. It's her car and I don't know what she makes and she's not the kind to ever bother and check how well it does.

 

FWIW, I've driven it a few times on trips to and from family holiday gatherings as she usually has me or my dad drive, and it shows to be making high 27-28ish going 70-75mph down the highway on the DIC, but I don't know if it's accurate.

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I'd just stick to a 3500. They've got plenty of power, I didn't thing the 3900 was that much better for the trade off in mileage. My mom's '07 Impala 1LT with the 3500, no kidding, has pulled 34 mpg on roadtrips. That's going off the DIC and the old fashioned check your mileage way. She easily averages 23-25 MPG combined and normal highway trips are in the 30-32 MPG range.

 

No engine issues, aside from having to add a little coolant. Seems to be common.

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