As for durability, the specialist may have confused the 4.0 with its replacement; the 4.2, which has very good free flowing heads, strong aluminum alloy block and bottom end. The 4.2 s/c comes with forged pistons, rods, and crank that is held down by 6 bolt mains, splayed in the same fashion as the Ford Mustang Cobra Terminator 4.6 s/c. Many feel the n/a 4.2 can support 425 chp and 650+ chp for the 4.2 s/c. Forum member, Avos, has an unmodified 4.2 s/c motor with a twin screw, belting out 635 chp (540 rwhp), and it's a daily driver. The problems we've encountered were durability of coolant expansion tanks and normal wear of top end items such as cam cover and spark plug well gaskets, etc.

 

Best to ignore him as he's clearly out of touch. Is he the one giving you the wrong meaning for OBD codes, too?

 

Another clueless fool!

Please ignore anything he says. The AJ V-8 was and is an excellent engine.
The first generation like many DOHC engines had timing chain tensioner problems. The 4.2L is pretty bullet proof.
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