Expected Power Output?

[TrenchFoot]

I was wondering if anyone can clear up a question that I've noodled on over the years. What differences exist between a 6.2 out of a HMMWV and J code engines? Specifically what makes the military engines put out more HP and torque?

I figure it's gotta be a mix of intake/exhaust manifolds, IP, injectors and precups, right? I'm curious because I am getting close to putting my rebuilt 6.2 into my Jeep and want to know what kind of power it'll make. It came from a '93 P30 stepvan and has all the best-from-GM parts for power:

599 block
J code, single plane intake
4979 IP
Precups: 3 dot, 'circle A'

I've only seen mention of the 'circle A' precups being from HMMWVs, but I suspect they were tossed in to any HD engine at the factory. Not that I expect they make a lot of power difference themselves.

Just wondering if I would expect this engine to make J code power or HWWMV power. While I'm bolting a Banks Sidewinder onto it, I'm curious what I should expect as base, NA power.

Thoughts?

[john8662]

Base NA Power 155 HP.

'567 Heads off 1990 or later 6.2's and 6.5's make more power due to more efficient injector angle and precup.

A NA 6.5 is rated at 170HP non-emissions version of course.

[TrenchFoot]

Thanks John, I forgot about the heads. I just always wondered where the info on Wikipedia came from. Seen it quoted a bunch of times:


Horsepower / Torque (at start): 130 hp (97 kW) @ 3,600 rpm / 240 lb·ft (325 N·m) @ 2,000 rpm
Horsepower / Torque (at final): 143 hp (107 kW) @ 3,600 rpm / 257 lb·ft (348 N·m) @ 2,000 rpm
Horsepower / Torque (US Army HMMWV model): 165 hp (123 kW) @ 3,600 rpm / 330 lb·ft (447 N·m) @ 2,100 rpm

Like everything else on a wiki, gotta take it with a grain of salt I guess.