3.1/3.4 crank in 3.9 LZ engine

[NateD4]

Has anyone else ever measured or test fit the 3.1 crank in the new LZ 3.5/3.9 block?

I've found the 3.1/3.4 crank appears to fit correctly. Has anyone else gotten this result.


Thanks

Nate

[geoffinbc]

Yea it should work fine. But the rod journals and the reluctor ring are different.

[NateD4]

Well I'm looking at performance cranks and using 2" big end rods. For some reason all my initial research said the 3900 used a different crank with larger main journals and was longer. It turns out to be wrong (another reason not to believe everything you read on the internet).


At this point I'm not really even sure what architectural changes were made to the LZ engine block compared to the previous LX blocks. The only thing I can see is the oil sprayer sand the Displacement on Demand oil valving passages.

I wish I had known that a few months ago. I missed a great opportunity on a crank for my project.

[geoffinbc]

The 3.9L also has the bores moved outboard. If you were to sight a straight line down the center of each of the bores the lines would not intersect at the main journal centerline they would intersect slightly below the crank centerline. The 3.9L and 3.5L VVT were made this way.