I have to disagree with you on one point woody, it takes a pretty sick 4.0 to not romp all over a 2.9.
No a 4.0 doesn't have much more power, but what it does have
is 32% more peak torque and up to 60% more torque in some
parts of the rpm band and in any event more torque ANYWHERE
in the engine's rpm band (1100rpm to 4600rpm) than a 2.9 is
capable of making.
Torque wins.
From personal experience after having driven well over 600,000 miles
in 2.9 powered vehicles and almost exactly 260,000miles in the vehicle
I'm driving now I can say that in a supercab with 4.10 gears a 4.0 CAN
actually be driven (but cannot accelerate from) at 1500rpm while a 2.9
has essentially nothing useful below 2200rpm, for acceleration anyway,
and for "Cruising" on level ground the 2.9 is much happier between 2600
and 2900rpm.
The 4.0 makes 200ft/lb of torque at 1100rpm and builds to a peak of 225ft/lb@2500-3000rpm* a 2.9 only makes 170ft/lb at it's peak at 2600rpm. and the 4.0 doesn't stop making 200ftlb of torque until it hits 4100ft/lb just below it's 4200rpm power peak, but even at 4600rpm (the power peak rpm of a 2.9) it's still making more torque than
the 2.9 CAN produce, even under ideal circumstances.
Yeah there doesn't seem to be "much more" there when you drive
a 4.0 once or twice and "Get on it" several times, but after you drive it
for several weeks or (better yet) a month or two, you quickly discover
that it's strengh is how it behaves when you are NOT "on it", it seems
to effortlessly do at 1/3-1/2throttle and ~2000rpm anything a 2.9 can
do even if the 2.9 is screaming it's heart out.
This is not subjective impression, this is objective reality.
Ths difference is much like the difference between a 300hp 327 chevy running
against a 325hp 396 Big block in the same chassis, this is something I've actually
done... twice...
Yeah, there's a LITTLE more power there, but the difference is that the big block
just doesn't have to struggle to do anything you ask of it.
where a pony would have to work HARD, those Clydesdales just motor on through....
*The 4.0's torque curve is relatively flat @~220ft/lb across a 600rpm range,
so basically anywhere between 2500rpm and 3000rpm can arbitrarily be called it's "torque peak" depending on which exact calibration and installation you
are refering to.
It is worth it?
That depends on your knowledge, skill level, available tools
access to cheap (read: JUNKYARD) parts and your attention to detail.
I had ONE wiring error (an unconnected ground) after completely rewiring
the entire engine bay, installing the '93 power distribution, the 130Amp alternator
cruise control rewiring my fog and driving lights and wiring in my dual tank system
AND converting my truck from 2wd to 4x4.
Though I should also point out that I learned wiring in the electronics industry and I could probably rewire most of the black boxes in the avionics bay of a Grumman A6
from memory even though it's been 20 years since I worked at Lear-Sigler.
AD