3900 versions and configurations for swap use

[Will'sFiero]

Correct
I doubt it, but I would imagine the compression distance is probably different, so you would probably need a set of rods that are a tad shorter than stock.

it would be cool, but I don't think it would be a drop in and go thing. FWIW, gmpartsdirect lists the 3.5 and 3.9 piston as the same.

The powdered metal conrod is much more expensive to make than a hypereutectic piston... I would expect that the rods would be the same before the pistons.
However, I could be wrong...

Per parts.nalleygmc.com

LZ9 conrod: 12609561
LZ4 conrod: 12609562
LX9 conrod: 12568557

LZ9 piston: 89018065
LZ4 piston: 89018065
LX9 piston: 12584528

Interesting... only conclusive about the LZ4 and LZ9 using the same piston... Consecutive part numbers for the two conrods is interesting... that typically means they were designed together as different members of the same family. That's also to be expected, as with using the same piston, the LZ4 needs longer rods than the LZ9. I wonder... Since they needed different rods ANYWAY, did they tune the lengths up slightly so that the LZ9 assembly has the piston further in the hole than the LZ4 assembly?

Ok, so no compression bump for using LZ4 pistons.

[ericjon262]

The oil filter adapter may need some diddlage to clear the Fiero front cradle crossmember.

if it's anything like my LX9, you can unbolt the filter housing, remove the oil filter threads from the housing (mine used a big allen wrench) and just install the threaded adapter right into the block.

Edit:

Threads visible here...

[Will'sFiero]

Will,
http://s296.photobucket.com/user/mrt...?sort=2&page=1

-Eric

This casting spans the front of the heads and has the radiator outlet and a heater core connection to the waterpump. Interesting difference from previous engines. I had heard of this part, but was under the impression is was on the BACK of the cylinder heads... which would make more sense for transverse mounting.
I'll have to see how well (or not) it works with the minivan exhaust crossover when mounted on the back... however, that would point the coolant outlet toward the trunk, which wouldn't make much sense either.

If use on the front of the engine, it looks like it puts the alternator mount location in almost exactly the right place for use in a Fiero as the dogbone mount.

The accessory drive will have to be worked a bit to mount the alternator low, about where it is on the 2.8.



A bracket could pick up the right two holes out of this 4 bolt pattern and the upper Fiero-style mounting hole.
Or an entirely new saddle bracket could pick up those two bolts and the forward two of the three bolt pattern on the other side (photo below) and not bother with the Fiero-style mounting holes.
The oil filter adapter may need some diddlage to clear the Fiero front cradle crossmember.





Good photo of the missing mount boss.

I don't know if the oil pan will work or not... it kind of looks like it's cut out enough at the front to make room for a Fiero engine mount, but I probably won't be able to tell until I get one. This is about the only photo I could find of it:



The heater hose connections are in almost the perfect spot to use the '85-'86 Fiero heater pipes:

[ericjon262]

The LX9 is the early 3500 with 94mm bore, right? And the LZ4 is the later 3500 with 99mm bore, right?

Correct

Are the wrist pins a different diameter between the 3500 and 3900? Why wouldn't LZ4 pistons just drop in?

I doubt it, but I would imagine the compression distance is probably different, so you would probably need a set of rods that are a tad shorter than stock.

I would expect that the 3500 pistons would be flat tops or at least have smaller dishes than the 3900 pistons. If both engines have 9.8 compression and the same head castings, then a 3900 with 3500 pistons would have 10.9 compression.

it would be cool, but I don't think it would be a drop in and go thing. FWIW, gmpartsdirect lists the 3.5 and 3.9 piston as the same.

[Will'sFiero]

The LX9 is the early 3500 with 94mm bore, right? And the LZ4 is the later 3500 with 99mm bore, right?

Are the wrist pins a different diameter between the 3500 and 3900? Why wouldn't LZ4 pistons just drop in?
I would expect that the 3500 pistons would be flat tops or at least have smaller dishes than the 3900 pistons. If both engines have 9.8 compression and the same head castings, then a 3900 with 3500 pistons would have 10.9 compression.

[ericjon262]

http://www.fiero.nl/forum/Forum3/HTM...-26.html#p1011


That's why... I asked on that thread if he meant using the 24x PCM for his next swap in order to try getting AFM/DOD working.

All 3900's are 58x, right?

as far as I am aware, the 24x PCM (0411) doesn't have provisions for AFM/DOD, just the later PCMs.

He's also using the F40, which lets him turn the engine slower.
AFM/DOD won't reduce frictional losses due to 6 sets of piston rings moving at 3000 RPM at 80, but it will reduce pumping losses from turning that RPM at light load, as well as moving the cycle to a more thermally efficient starting pressure (increasing the effective expansion ratio on the power stroke).

sure, but how much is there to be gained?

Thanks! I'll take a look.

Thought: Can I swap LZ4 3500 pistons into an LZ9 engine to bump compression? Are the piston dish/dome specs around anywhere?

Probably not without custom rods. IIRC, Joseph Upson used LS1 pistons in his LZ9, might be a cheaper route than trying to make LZ4 pistons work.

[Will'sFiero]

Will,

I figured you've probably seen all this, but if not, thought you might like it.

LZ9 build thread (died before complete, but still lots of info,)

http://60degreev6.com/forum/showthread.php/41450-3-9L-LZ9-engine-internal-upgrade-amp-performance

Pictures that go with the thread.

http://s296.photobucket.com/user/mrt...?sort=2&page=1

LZ9 article (not much but still kinda neat.)

http://60degreev6.com/forum/local_links.php?action=jump&catid=14&id=55

-Eric

Thanks! I'll take a look.

Thought: Can I swap LZ4 3500 pistons into an LZ9 engine to bump compression? Are the piston dish/dome specs around anywhere?

[Will'sFiero]

it's not bad at all, and that was without DOD/AFM, and a 5.3L Vs. a 3.9L with VVT. which makes me think the AFM/DOD wouldn't be worth the work unless you netted a huge gain in mileage from it.

He's also using the F40, which lets him turn the engine slower.
AFM/DOD won't reduce frictional losses due to 6 sets of piston rings moving at 3000 RPM at 80, but it will reduce pumping losses from turning that RPM at light load, as well as moving the cycle to a more thermally efficient starting pressure (increasing the effective expansion ratio on the power stroke).

[Will'sFiero]

Thanks. My biggest concern with the system is trying to get it to work with a manual trans. if Paul couldn't make it work with a much more decoded V8 PCM, I would bet it will be on the verge of impossible with a V6 PCM all the big tuning companies don't make money on.

http://www.fiero.nl/forum/Forum3/HTML/000123-26.html#p1011

Originally posted by fieroguru:

Nope. The E67 ecm requires the BCM for the brake switch input and my swap doesn't have one.
DoD has been proven to work w/o the BCM, so my next LS4/F40 swap will use that ecm for further testing.

That's why... I asked on that thread if he meant using the 24x PCM for his next swap in order to try getting AFM/DOD working.

All 3900's are 58x, right?

[ericjon262]

Will,

I figured you've probably seen all this, but if not, thought you might like it.

LZ9 build thread (died before complete, but still lots of info,)

http://60degreev6.com/forum/showthread.php/41450-3-9L-LZ9-engine-internal-upgrade-amp-performance

Pictures that go with the thread.

http://s296.photobucket.com/user/mrt...?sort=2&page=1

LZ9 article (not much but still kinda neat.)

http://60degreev6.com/forum/local_links.php?action=jump&catid=14&id=55

-Eric

[Will'sFiero]

www.car-parts.com does not list the LZ8 as an option in the '08 Impala, just the LZG. The LZ8 is only available in '07.
Not that there's any real difference between the engines...

The LZG's are actually more common in junk yards, apparently.

[Will'sFiero]

I'll talk to Sinister about setting up a PCM when I'm ready to do the swap. The G6 GTP was the only 3900 used with a stick, but the Impala was the only one with AFM/DOD. Putting together a calibration will take a little cutty/pastey, but the data's all there.

I could snap some pics of the mount bosses. But there is a 3 bolt flange on the left/drivers side of the engine and a 4-bolt/jack shaft flange on the right/passengers side.

The 3500 oil pan may be the same but I don't know for sure. Either way it has very similar dimensions.

I believe the non-AFM lifters are the same as the 3500 lifters. But again not 100% sure. And I know that the 3500 lifters are different from any SBC lifters, although the internal components may be swappable.

Pics would be handy... not just of the bosses GM used, but of the missing bolt location also.

[ericjon262]

it's not bad at all, and that was without DOD/AFM, and a 5.3L Vs. a 3.9L with VVT. which makes me think the AFM/DOD wouldn't be worth the work unless you netted a huge gain in mileage from it.

[caffeine]

Or maybe the shift changes would be unpredictable to the PCM and the AFM switching would be too 'klunky' feeling? With an automatic the transition could be made hardly noticeable.

[Will'sFiero]

by AFM I'm assuming you mean cylinder deactivation or DOD correct? I know Paul(Fieroguru) was working on trying to get DOD to work on his LS4/F40 swap and couldn't get the programming to work. AFAIK, there was no DOD manual trans combo offered by GM.

Thanks. My biggest concern with the system is trying to get it to work with a manual trans. if Paul couldn't make it work with a much more decoded V8 PCM, I would bet it will be on the verge of impossible with a V6 PCM all the big tuning companies don't make money on.

I hadn't heard he was having problems... Last I read he was knocking down 28 mpg on the highway with 380 RWHP... not a bad combo.

I assume GM never offered AFM with a stick (C7 Corvette?) because the transition would be perceptible with a manual transmission.