Isn't your last statement why the XJ stopped passing safety guidelines and was discontinued? It was actually too stiff? I don't think concrete bumpers would work well with performance and economy, haha...
Yeah, probably. And on the cement bumpers as well. Perhaps use 3/4" plate slab to make bumpers fore and aft?
PAIR of 4bts??? Sorry, don't know enough about military trucks... seems crazy! How can you even get two cummins in a truck anyways? I'm intrigued...
M113 Gavin APC - used from Vietnam forward, and used by NASA for personnel transport as well (but I'm not so sure why.) Strip some of the armour-plate off and replace with lighter steel - could probably drop a solid tonne that way. Plenty of room inside. Just need road tyres (pix below.)
"DIS/COP top plug Hemi head, cross-draught? Perhaps GDI as well? Hmm..."
Lost me with all that tech talk... haha.
DIS - Distributorless Ignition System
COP - Coil On Plug (DIS may be COP or "remote coil" setup)
Cross-draught - manifolds on opposite sides of the head, as on V-block engines, and most four-cylinders. The cross-draught head breathes more efficiently than the side-draught head (like we've got.)
GDI - Gasoline Direct Injection. Allows for a "totally dry intake" setup, and results in an FI setup similar to that on Diesels. Mitsubishi, MBZ, and Bosch are all working on a viable setup, but it's not caught on yet.
I would think a good balance job can do much better for the 2.5, because while it normally doesn't NEED to wind up that high RPM, it can much more safely than the sixes because of its' much shorter stroke...
True - the inline six in general suffers from harmonic trouble. Not so much due to the stroke, but due to the length of the crankshaft. Ferrari gets away from the problem with their horizontally-opposed 12-cylinder by dint of having two inline sixes stuck together at the sump rails - resulting in opposed forces to reduce harmonics. Very smooth engine.
Would an *extreme* offset grind also potentially cause problems with bearing oiling? Wouldn't a custom piston pin height be required after only a couple thousandths of offset, in order to not screw with quench?
Talking more through my hat than anything else - I've not crunched the numbers on that. I don't know what clearance there is between the piston deck and the block deck at TDC, you should be able to go right to flush and select a head gasket to set quench (by compressed thickness.) If you go "proud" (piston deck above block deck,) then you're really going to want to look into altering rod length or piston compression height - with the latter being preferred, as shortening the rod will also reduce TDC dwell time, meaning you've got less time to develop peak combustion pressure (TDC dwell gives you more time to develop pressure, with absolute peak being somewhere around 12ATDC at the crankshaft for maximum "push" at maximum leverage. Please, don't ask how I know all of this, or I'll fire back with a handful of titles that make very dry reading...)
Granted, there's only so much you can do to move the piston compression height - you generally don't want to put the gudgeon pin bore where it will intersect with the oil control ring groove. You can always shorten the ring pack height, but then you have to deal with piston rock in the bore, and that's its own problem (doable with short-stroke engines, but not so much with longer strokes. The typical F1 engine probably runs about a ring pack about half as high as ours, but two-thirds of the stroke is tops for them as well. That's got a lot to do with why they can run 10Krpm all day long...)
If you're going to build a long-stroke engine to maximise torque, you're not going to need to balance it for high-RPM operation. "Stroking" a gasoline engine starts heading you into Diesel territory. Ever wonder why the redline of a Diesel is so low (typically 3000-3500rpm?) It's got to do with both the compression ratio (16:1 or higher) and the length of the stroke (piston acceleration/deceleration and stresses on the gudgeon pin, connecting rod, and crankpin.) Push the stroke too far, and you'll have to push the redline down to compensate.