| I'm pretty sure the 5.2 and 5.9 use different blocks.
The 5.2 and 5.9 share the same block family but use two different castings.
Bore centers are identical but the 5.2 has a 3.91 stock bore and the 5.9
has a 4.00 stock bore.
The 5.9 also has a larger main journal size (you'll note oil pans can't
interchange because of this).
The larger journals were originally engineered to support a switch to cast
cranks. All previous 340 and 318 (5.2) had used forged cranks. Some claim
that the larger journal size was to support the increased stroke from 3.31
to 3.58". They are simply wrong, it happens. I have a 318, a 340, and a
360 block sitting in the garage right now (and a couple of 440 assemblies).
A man has to have choices....
The new generation 4.7 is 150lbs lighter than a 5.9. The weight savings
extends beyond just the obvious differences. The actual 4.7 iron block
with bedskirt is far lighter than a 5.9 iron block with iron mains. Even
large internal parts like the rods and crank are lighter.
I'd love to have a spare 4.7 to put in my Barracuda. 11 to 1 compression
and wicked cam profiles. Aftermarket fuel injection and a few tweaks.
That would make for the perfect 2800lb autocrossing pony car!!!
-Steve Ekstrand
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