LX9 vs LZ4 differences. Top swap on 3.4L. Gurus co

[bachert24]

There are a million hybrid 3.4/3400/3500 engine posts out there so I want to be clear with this. People are basically just saying you want 3500 heads and intakes. But there is a huge difference between the different 3500 engines. Mainly I am looking at the LX9 and LZ4 engines. The LZ4 is a dohc engine and has a completely different cooling system. I haven't bought heads yet, but I did pick up an LZ9 lower intake with fuel rail, injectors, and harness. Now the question is, is it possible to swap this intake onto the 3.4L engine? What will it take? Heads from the same engine code? Modifications? Impossible? I know the LX9 heads and intake are bolt-on, but what about the LZ4? Please chime in here and let's figure this out so we don't have other people buying the wrong parts. Can someone also get me a clear detailed pic of the top of an iron head 3.4L without the heads or intakes on it? Thanks a bunch!

[Guest]

The LZ4 is not a DOHC engine, it is still an OHV engine.

I haven't been able to find any good pictures of the LZ4/9 heads alone, or the blocks to see if the pattern is the same to even start there.

IIRC the bores were shifted on the VVT engine (LZ4/LZ9), which would likely render them incompatible with any sort of typical hybrid swap.

I'm trying to find more information, but if it was a possible head swap, I'm sure there would be a number of them done by now.

[bachert24]

Thanks Raven, always a huge help! Let me know if you come up with anything. Can you possibly recommend good cam specs to look for? Wot recommended one and I want to make sure it's correct for maximizing hp. Thanks again!

[bszopi]

When I get home I'll take a look, but I think there is info on why the LZ engines are different than the typical 3x00.

[bachert24]

Awesome thanks, let me know! I can't find anything without reading everything on the internet.

[caffeine]

IIRC the heads will physically bolt on but won't work because the bore spacing changed.

[carbon]

The 3500(LZ4) and 3900(LZ9) are only different by displacement dimensions and intake design... this is a great thread: 3900 Info

This too... 3900 Pictures

[bachert24]

Ok I can now confirm first hand that the lz4 lower will not work. The 3400 upper intake doesn't line up with the lower intake at all. not even close.

[trebec]

not sure if this helps, but the casting number for lx9 heads form a malibu are 125785823, but pontiac g6 heads are 12578525. is there a difference in 3500 heads?