What are the differences between the heavy and light-duty 5.9L gas engines in the '94 Ram? The heavy-duty uses larger spark-plugs so I'm curious what other differences I'll run in to.

I've got a '94 DRW 3500 that's supposed to have the heavy-duty in it and doesn't.

 

I wasnt aware the engine was different at all myself?.... I thought things like the radiator and coolers were the main differences... in packages
I'm curious too since this is the first I've actually heard of a heavy and light duty gas 5.9... I thought thats what the diesel (also a 5.9L and avaliable in two versions but doesnt use spark plugs at all so? )or v10 was for?...... according to wiki there was only one 5.9l gas option... I also have the original sales broshures but I'm not curious enough to dig them out right now...

 

The only differences in the motors I've ever heard about were that they were tuned differently, just that the heavy-duty was tuned for more towing

 

I thought there was only one gas 5.9 too. If tuning is different I wonder HOW different it is...and what trucks were these supposed to be in? Hmmm...

 

i was curious about this too. i've heard a little bit about heavy duty engines but wasnt sure what the differences were. i know the 4th gen rams have the light duty and the heavy duty. the LD has something like 390 at the fly and the HD has about 380 at the fly. wasnt sure if this was because of different internals of just the tune thats put on it. im curious to see what other people have to say.

 

what are those numbers your quoting? the 390 and 380? they arent hp or torque...

 

How cant it be? He said it was in the 4th gen

 

Well to be honest, any 360 I've ever seen might as well be called a heavy duty.

 

There were in fact 2 different sales codes used for the 5.9, light duty was EML and heavy duty is coded as EMM. Besides bigger rad and trans cooler etc I believe the only difference was the EMM used a slightly different cam to lower the peak torque rpm. Kind of like the R/T used a different cam to achieve that extra 15 hp.

 

the numbers are the advertised flywheel horsepower of the 5.7LD and the 5.7HD in the new 4th gen rams

Light duty has 390 advertised horsepower at the flywheel
Heavy Duty has 383 advertised horsepower at the flywheel