3900 Info

[Joseph Upson]

The 3900 injectors are 27.8 lb/hr at 400 kPa Multec 3.5
The 3500 injectors are 24 lb/hr at 380 kPa Multec 2

I have a set of 30 lb/hr @ 300 kPa injectors that are the same dimensions as the two above so I guess I'll need to turn the pressure up to 400 kPa to get the most out of them.

[CNCguy]

Cool... Thanks Joseph

[Joseph Upson]

Well, I've ordered a 6 speed transmission and hope it will arrive with all that was paid for in one piece. My problem now is after looking at the Desktop Dyno comparison again there is a roughly 40 plus horsepower and torque gain over the 3500 with the same cam installed and at the same boost level. I'm not quite ready to settle for the 3500 as of yet.

With the info I PMed you on the possible small block chevy roller bearing fitment which has the correct internal diameter for the 3400 cam, do you have enough room at the front bearing circle to mearsure it's bore diameter for confirmation of my suspicion that the 3900 has small block cam bearing specs.

Also when you get a chance, how about a good picture of the front of the block without the cam.

And please continue to search for a quick and easy way of fixing the cam into position.

Next to the immunization clinic I visited yesterday is a company that manufactures bearings, in retrospect why I didn't go in and inquire about custom applications is beyond me. Hopefully they are open Friday so I can walk in with the V6 bearing sample I have to see if they can duplicate it to different specs.

[CNCguy]

.......With the info I PMed you on the possible small block chevy roller bearing fitment which has the correct internal diameter for the 3400 cam, do you have enough room at the front bearing circle to mearsure it's bore diameter for confirmation of my suspicion that the 3900 has small block cam bearing specs.

Also when you get a chance, how about a good picture of the front of the block without the cam.

And please continue to search for a quick and easy way of fixing the cam into position.

.... Hopefully they are open Friday so I can walk in with the V6 bearing sample I have to see if they can duplicate it to different specs.

I will be pulling the cam out this weekend to get some measurements... hopefully there is enough room to measure the cam bore size of the block. I will also get some pics posted of the block front.

After we get these two rush molds finished, I am planning to make a couple of the prototype VVT eliminators. I have the design finished and it will probably be around two weeks or so. The adapter will allow about 30 degrees of cam adjustability and will require stock cover to be modified to get enough clearance. Around .06" will have to be removed from the inside of the cover.

Did you get a chance to stop by the bearing place? Thick walled bearings may be the easiest route at this point.

[Fiero11]

Don't forget the 3.5L gasket on 3.9L head picture.

[Nightingale]

I know I will be ordering a vvt eliminator and a CPS as soon as I find a decent 3900 around Ohio. Nearest one I've seen on car-parts.com listing was in Michigan *sigh*

[CNCguy]

Forgot about the follow-up pics.

3900 Head with 3500 gasket


Another shot


Marked area where gasket fits


3900 gasket over same area


Shot of 3900 head showing coolant passages


Pic of coolant passages in older heads - notice location of holes around head bolts compared to 3900 heads.

[CNCguy]

I know I will be ordering a vvt eliminator and a CPS as soon as I find a decent 3900 around Ohio. Nearest one I've seen on car-parts.com listing was in Michigan *sigh*

AHHHHH... the CPS bracket doesn't fit the 3900. They changed the damn holes for that area. But we plan to make some for it in the near future. Still not alot of them available yet but that will change with time and so will the prices.

BTW... A Beretta with a 3900 would be nice.

[Guest]

the firering of the 3500 gasket doesnt' hang off into the combustion chamber of the 3900 head does it?

[onefastV6]

For those that are not already aware:

"This new generation V6 allows a high level of flexibility, with common castings over a range of displacements. The 3.5L (LZ4) V6 shares its block, pistons and cylinder heads with Powertrain’s new 3.9L (RPOs LGD, LZ8 and LZ9). A common bore measures 99 mm; displacement is increased in the 3.9L with a longer stroke (84 mm, compared to 76 mm for the 3.5L). The two engines share 80 percent of their parts."

Here are a few pics I found of the LZ4 3500

[CNCguy]

Nice pics Phil.... I was wondering about the intake & heads of the 3500. It doesn't have the variable intake but appears to use the same LIM since it uses 4 bolts per side. Wonder if the 3500 UIM may be a better choice if running the 3900 with the variable intake disabled?

the firering of the 3500 gasket doesnt' hang off into the combustion chamber of the 3900 head does it?

Yeah... by about .04~.06 on the intake side and lest than that on the exhaust side.

[Guest]

damn that sucks.

[Nightingale]

Any more info availible on the 3900 pistons such as wrist pin height, rod length(small and big end sizing as well). Would be nice to find some forged parts out there that we can possibly use in our application.

[Joseph Upson]

Any more info availible on the 3900 pistons such as wrist pin height, rod length(small and big end sizing as well). Would be nice to find some forged parts out there that we can possibly use in our application.

How about pressing for the bare minimum to make it work properly naturally aspirated first, I really want to do the swap but having my hands tied already with the 6spd I can't add to the madness with the cam spec situation and VVT still in the air. Ever do a swap that didn't work.

[Nightingale]

Well Worst case scenario would be to just swap over the whole wiring harness, and transmission (already been considering it since there is more aftermarket for the 4t65e-hd then my th125c or the 282 getrag). So I am just trying to look and see if there is anything out there from other applications that may be able to be used in the 3900 application.