3900 Info

[SappySE107]

Article on rocker arms

[CNCguy]

The nwer heads all use an 8mm stud, so if the pedestal could be swapped over from an 03 3400, those rockers might work.

The shafter diameter seems to be the same from what I measured, so the new style will mount on the old pedestal.

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

If you could bring a 3500 head that would be good since I have access to a non VVT 3500 locally but prefer not to pull the heads.

[CNCguy]

I could be wrong... but this thing has some pretty big ports for a 60V6. Here are some pics comparing the '06 3900 intake ports to an '00 3400 LIM. The ports are almost 3/8" taller and 1/8" wider. Makes sense why they made the rocker pedestals shorter. They raised the runner roof considerably.

Anyone have any thoughts on what the nasty black stuff is inside the runners. It looks alot like oil and crud from an EGR but this engine has no EGR. Any possibility that it would be from the VVT, exhaust coming back up???? Thoughts?

Also, note that there are no coolant passages to the intake.





3900 vs. 3400 runners





Manifold comparison



Inside the head (bad pics)

[SappySE107]

Yeah, its probably the VVT doing the EGRs work. Tall is good Ill bring a head with me and a lower intake as well to see how it matches up width wise.

[brad]

Wow, interesting stuff, thanks for the photos and info!

[AaronGTR]

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.

There's definitely a significant amount of changes made to this engine compared to the 3400/3500. There are some pics on here somewhere of a cut-away engine display I took at the north american international auto show. The top end will NOT bolt to earlier engines though. Due to the unique shape, size, and position of the ports on the upper and lower intake manifolds they can only be used with the 3900 heads. And the 3900 heads can't be used on earlier engines because the 3900 has offset cylinder bores.

It's obviously a technological jump from the older engines, but IMO the 3900 still doesn't make enough HP considering the half liter displacement increase, variable cam timing, and everything else. Especially considering the HP from competing manufactures V6's that are only 3.5L. They should have been able to get more from it.

[Will'sFiero]

Yes, Nissan gets 280-300 HP from it's 3.5 litre V6.
At the same specific output as the LS6, the 3500 should make 248 HP, but it obviously doesn't.

The only explanation I see is that GM just isn't serious about any kind of performance that's not V8 RWD.

[Fiero Brick]

I really think it is somewhat unfair to compare the 3500 and 3900 engines to higher-revving, highly advanced DOHC 3.5 liter engines that are often running with a high enough CR to justify using premium. Those two engines aren't made with the purpose of a high specific output. They're made to be modernized, reliable, economical pushrod engines that produce low-end torque to move some fairly big cars. It just isn't fair to put them on the same scales. They're called a high-value engine for a reason, y'know?

If you want to point to a GM engine to compare to the high specific output v6s in production by other manufacturers, you want the high-feature engines, namely, the 3.6 DOHC with variable valve timing, variable intake manifold geometry, soon to have direct injection. Then you're on level playing ground, in my opinion.

[Joseph Upson]

I really think it is somewhat unfair to compare the 3500 and 3900 engines to higher-revving, highly advanced DOHC 3.5 liter engines that are often running with a high enough CR to justify using premium. Those two engines aren't made with the purpose of a high specific output. They're made to be modernized, reliable, economical pushrod engines that produce low-end torque to move some fairly big cars. It just isn't fair to put them on the same scales. They're called a high-value engine for a reason, y'know?

If you want to point to a GM engine to compare to the high specific output v6s in production by other manufacturers, you want the high-feature engines, namely, the 3.6 DOHC with variable valve timing, variable intake manifold geometry, soon to have direct injection. Then you're on level playing ground, in my opinion.

I agree fully, the GM 3.6L DOHC put's down serious numbers, as high as 275HP in stock form with a red line as high as 7000 rpm and has a forged rotating assembly; crank, rods and pistons and still runs on regular unleaded. I guess GM was really pushed to develop it because of Gas prices and competition since it has found it's way from the cadillac and select SUVs to several production cars for 2007 including the Pontiac G6 where it is attached to a 6-speed automatic that has a 4.48 first gear for when you really, really need to get out of the hole quick. The 3900s moment in the spot light has a huge shadow not its own growing in it. Take a look for yourself:

http://media.gm.com/us/powertrain/en/product_services/2007/07car.htm

[Fiero Brick]

Exactly. I'm glad to see this engine being used more, but somewhat dissappointed that it isn't going into any lighter-weight, sportier vehicles.

Also, when comparing the Cadillac 3.6 to other engines with similar features and displacement, one also has to concider that it's the flagship engine and/or goes in the flagship sports vehicles of some other companies. CoughNissancough. Thus it can have more attention devoted to it, and nobody has to worry about stepping on the toes of other engines or other divisions' sportier cars. I'm pretty sure GM is still up to its old stinky stuff with limiting the 3.6's power output to keep from hedging into the territory of other engines. Sigh.

Thanks for posting that link, too. I've never seen that before, very interesting.

[CNCguy]

An update on what I'm finding on this engine.

The camshaft has larger journals, 51.5mm vs. 47.5mm. The center tube has been increased in diameter as well as the lobe base diameter (35.5mm) and has .293 lift at the cam. The front journal is wider and has a groove for oil flow to the VVT actuator. The overall length and spacing of cam, journal and lobes are unchanged.

The rockers weigh 145g vs the old one at 161g (weights includes the stunion shafts).

Intake valve is 1.87 dia. and Exhaust valve is 1.51 dia.

Ex. Push Rod 6.17"
In. Push Rod 5.88"

The oil passages has been rerouted from the oil filter. It now runs to the front of the block and then up to the cam area.

The holes on the front of the block have changed. I thought that they had only left out one of the mounting holes but they also moved the one below it.

[Joseph Upson]

It does seem a little limited in overall output relative to the increased displacement and VVT addition but I'm still holding off on installing my 3500 in favor of a 3900 specifically because of the benefits that can be had with the oil jets for the pistons making it much more boost friendly with its high compression. An oil cooler would further that advantage. The larger valves and head ports would probably result in an exceptional response to mild boost levels and who knows how much of the power output is limited by GM. They are already posting different numbers for the 06 and 07 3900. What I would like even better is to get the 3.6 DOHC. Who knows, I was fortunate enough to get the 05 3500 for a great price, maybe I should keep my eyes open a little wider.

[bszopi]

As mentioned by Colin awhile back (when he first got his hands on a 3500), it wouldn't be that difficult to plumb the existing oil squirter to 2 additional oil squirters so that all cylinders are covered.

[Joseph Upson]

As mentioned by Colin awhile back (when he first got his hands on a 3500), it wouldn't be that difficult to plumb the existing oil squirter to 2 additional oil squirters so that all cylinders are covered.

That's to much work for a 3500, I want the extra .4 litres minus the added risk of making a plumbing mistake and having 3 squirters with plumbing riding around in a circle on the crank should it come loose. I suspect there is also the issue of having the right spring pressure in the pump for the additional free flowing tips also, that would be a disaster waiting to happen were it not corrected before adding two turbos for a further pressure drop.

I originally planned on using the 3500 but I have a few 3900s near by getting closer to my price range. I was planning to use two .60 compressor .48 turbine housing T3s and look at what I found for $25 at a core shop, complete and brand spanking new, I took the wastegate actuator and tail end off to find out why it was seized, turned out there was a piece of cleaning brush lodged against the turbine wheel so someone thought it was no good, my blessing, now all I have to do is refresh the one I already had. This ones .60 cold .63 hot, very popular for the early ford and chrysler cars

[onefastV6]

What I would like even better is to get the 3.6 DOHC. Who knows, I was fortunate enough to get the 05 3500 for a great price, maybe I should keep my eyes open a little wider.

You mean, like this?

http://cgi.ebay.com/ebaymotors/Buick-Lacrosse-3-6L-Engine-Rendezvous-7-Mi-Motor_W0QQitemZ230030935685QQihZ013QQcategoryZ33615QQrdZ1QQcmdZViewItem