3900 Info

[CNCguy]

I recently bought an '06 Impala 3900 & 4T65E tranny. My reason for the purchase was to find what would be needed to swap it into older cars and RWD vehicles. What I have found so far is kind of interesting. I have only removed the UIM, exhaust manifolds, TC cover, coolant return system, PS pump & valve cover.

Excluding electronics, the engine with Impala brackets will bolt into a W-body.... no mods required except you would need to use the Impala AC comp, alternator and a very long upper radiator hose. The U cooling system and VVT require that you use the front covers for the 3900.

The length of the engine and heads are the same as the 3X00 engines. Spacing between exhaust ports is very close to the 3X00 but the bolt pattern is completely different (Holes are diagonal). Exhaust ports are larger also.

LIM does not have coolant passages. The U cooling system pushes the water into the front of the block on each side, it circulates through the engine and exits from the end of the heads above the TC cover (exits through the freeze plug openings in the heads). The coolant return system bolts to both heads and holds the PS pump and alternator. The alternator mounts different than 3X00s that I have seen and is a 125 amp Bosch. The thermostat is located on the inlet side of the water pump.

The heads have 4 mounting holes in each end and the pattern is different than earlier models.

LIM, UIM, TC cover, coolant return and water pump use metal gaskets with molded rubber inserts. They look like they will be expensive to replace, who knows.

The 3900 uses a 70mm electronic TB and the UIM will accept a 76mm without porting. I am going to make an adapter to mount a 75mm TB from a 5.3.

The camshaft has a hub that extends about 3/4" from the face of the block. It is used for the VVT feature and will not allow the old style TC gear & cover to fit. I have not removed the cam yet to see if an old style cam can be used. Also, a chain tensioner is used instead of a guide.

All of the TC cover bolts are M8 instead of having (5) M8, (2) M10 and (3) M12 bolts on previous models. One of the three bolt holes on the front of the block that were used to mount the engine was eliminated. The 3900 only has one hole on each side of crank.

I need to get some pictures to post, perhaps I can do that this weekend. Let me know if there is something special you would like to see.

I'm really curious about the operation of the VVT. It only uses two wires to control it. If anyone has any info on it's electrical operation, I would appreciate the input.

[Jacque8080]

I'd like to see picture of the mechanism that varies the cam degrees.

I'd just like to congratulate you on the purchase. It's more advanced to the 7.0 liter engine in the Z06 with respect to the VVT.

The future of the 60degreev6 is a bright one.

[SappySE107]

Pics Looks like I need a new bench so I can flow the larger bore heads. Very cool on the adapter to go larger TB Is the 5.3 electronic as well?

[ProjectMM]

As to my knowlage the cam is completly different, the jurnals are larger on the newer cam. there are many topics on here that describe the differences.
and also some great pics

[Fiero11]

Can the lower intake be rotated 180 degrees as with the 3400 so the water would come back out the front for rear wheel drive?

[CNCguy]

I was only planning to take some of the external measurements from this engine but as I go along, I see more that needs to be checked out. I may be wrong but it appears as though the whole top end may bolt to the earlier engines. Time will tell.

Can the lower intake be rotated 180 degrees as with the 3400 so the water would come back out the front for rear wheel drive?

The coolant exits from the front of the heads, above the timing chain cover. The LIM appears as though it can be rotated. I will find out soon and let you know. We are planning to put this engine in a MG for fitting and some testing. The biggest obstacle seems like it will be clearing the VVT setup.

Ben... the 5.3 TB uses a cable.


Here are some pics of the 3900.

Front of engine - notice coolant return holes and extra mounting holes in end of heads - one hole missing for lower mount on some models.


Rear of engine


Coolant return system - also mounts PS pump and alternator


Exhaust port and staggered bolt pattern


Rocker arms


Timing chain cover


Typical gasket constuction - looks expensive

[onefastV6]

There has been speculations before that the 3900 rocker arms will not fit the previous gen 3X00 engines.

Now that the engine is here, do you have any idea if they will bolt to the 3100,3400, and 3500 engines? Also anyone hear what ratio they are?

[Will'sFiero]

The coolant exits from the front of the heads, above the timing chain cover. The LIM appears as though it can be rotated. I will find out soon and let you know. We are planning to put this engine in a MG for fitting and some testing. The biggest obstacle seems like it will be clearing the VVT setup.

The coolant circulation arrangement is reminiscent of the FWD Northstar setup, just on the other end of the engine.

Typical gasket constuction - looks expensive

Looks reuseable.

[CNCguy]

Looks reuseable.

True.... as long as it doesn't stick and tear when you pull it apart. This one was stuck in a couple of places and tore a little off the top of the sealing bead around the water passages. I ended up using a thin putty knife to slide behind it to get the rest of it loose. This one should reseal fine with a little silicone in the rough areas but I wonder if higher mileage gaskets can be saved.

Anyone pulling one of these engines apart needs to use caution if they want to save the gaskets.

[gpse3400]

That tb looks like the 4.3 70mm I ran with...Is this cooling system reverse flow like the LT1?

[CNCguy]

There has been speculations before that the 3900 rocker arms will not fit the previous gen 3X00 engines.

Now that the engine is here, do you have any idea if they will bolt to the 3100,3400, and 3500 engines? Also anyone hear what ratio they are?

They are not interchangable for sure. As you can see, the new style has a much shorter pedestal and uses a smaller diameter bolt. It looks as though the rocker mounting boss has been raised on the head (unsure why, maybe port clearance or weight savings). Using calipers, the center to center distances appear to be the same as earlier models, so I assume the ratio is the same.

[CNCguy]

That tb looks like the 4.3 70mm I ran with...Is this cooling system reverse flow like the LT1?

I think the 5.3 TB is the same pattern, just has larger bore.

I do not know how the LT1 is set up, all that I know is that GM calls it U flow. The coolant goes in the front of the block and out the front of the heads.

[SappySE107]

Damn, I should scan the article I was reading about rocker arms in relation to their swept distance across the valve tip. It was mostly about stud vs shaft rockers but was interesting how the fulcrum to tip distance could equate to hp. The nwer heads all use an 8mm stud, so if the pedestal could be swapped over from an 03 3400, those rockers might work.

What parts should I bring when I come out? I have rocker arms off a 3500, 3500 heads, crank, block, etc. Dunno what all I can haul for crank/block but it really depends on what all you are gonna have torn down

[onefastV6]

Damn, I should scan the article I was reading about rocker arms in relation to their swept distance across the valve tip. It was mostly about stud vs shaft rockers but was interesting how the fulcrum to tip distance could equate to hp. The nwer heads all use an 8mm stud, so if the pedestal could be swapped over from an 03 3400, those rockers might work.

What parts should I bring when I come out? I have rocker arms off a 3500, 3500 heads, crank, block, etc. Dunno what all I can haul for crank/block but it really depends on what all you are gonna have torn down

Ben if you could get a copy of that article, I would like to read it.

I will bring the RSM Supercharger, Tranny mount, and hydraulic motor mount if I can get my hands on a used one. If there is anything else that I might have, let me know and I will add it to the list.

[kflo 93 gt]

I guess I hadn't seen or read much about these engines yet, so this is really nice to see. Especially with the pictures, good work as always.

One thing that really sticks out to me is the damn distributor drive gear plug set up, with all of the new parts on this engine I would've thought they could have done away with that by now. Kind of makes it feel like home though too.