This inquiry is based on owning an 89 3.9 and a 94 5.2. my fuel average for our type driving is 20mpg for the 3.9 and 17 for the 5.2. Both trucks have roughly 130K for mileage.

Seeing all the posts on engines old 3.9 old 5.2 then the magnum series.
1. What is the diff. between std engine and Magnum, output wise torque.

2. How much trailer load will a v-6 actually handle, not the suspension capacity, the actual power/torque to pull on a trip. Modified or stock.

3. I read mods to 3.9 to increase power, sound gas mileage etc. but wouldnt it be cheaper to just do a stock 5.2 concentrate on mpg. verses the thousands spent to get the 3.9 performance?

Speak up guys. I totally believe there is no substitute for inches. Any opinions?

 

A1: The increase in torque is from Chrysler redesigning the heads (92' for the 5.2l) to increase lower lift airflow. The valve diameter was increased as well (compared to the venerable 318). I believe the compression was upped a few tenths. The 5.2l also has a .430 lift cam with the 1.6 rockers (older engines used 1.5 rockers and a little bit lower lift cam). If I am not mistaken the 5.2l head has more compression (smaller chamber) than the 5.9l due to the piston height, which is arguable from different sources.

A2: I would limit trailering to your GVWR on high speed trips (interstate), but wouldn't mind pulling 2 tons through town or regular highway use.

A3: your right, it is cheaper to keep her, but engine swaps and mods are about conquering the powers that didn't offer what we want, when we want it, for less than we want to spend. Unless you get all the modding pieces for free, then the gains realized will not pay for themselves over the average life of a vehicle (kinda like paying 10 grand more for an electric hybrid that takes 9 years to start getting a return on the cost of fuel). Really, it is about bonding with our machines, kind of corny, but never the less true. Another forum member wanted 400 hp with 25mpg return with a truck. I hate to say it, but these Dakota do not slice through the air like a foil (or a Corvette, Bugatti etc.), so unless you get the drag coefficient down below 0.30 then it ain't gonna happen. Another option is to build the rear of your truck into a reverse foil to reduce side load drag, but I do not see that happening either.

 

1. understood now.
2. My thought is the 89 3.9 runs the same rpm at 50 mph as 94 5.2 but the torque diff. is so great the 3.9 shifts much more often in the hills which is understandable, once again inches. I read the 400 hp with 25mpg and agree with you.

Another thing not understood by most here is when you raise your truck you increase the drag because of the amount of air working on the undercarrage as well as the rest of the truck. I raised my 94 because A.it is a work truck and weight is carried. B. I would rather sacrifice a MPG and have the ride height I had on my 2004 because it is just more comfortable for me to acess and exit. C. In the past life of the truck the gas tank had some type of work done and the plastic tank has marks on it that I dont want to doplicate since some numnuts did not re-install the skid plate. That combined with Jr. Mechanic lowering the front of the truck to Honda height aint my idea of a truck. OMG you should have seen the headlight positioning when I first drove it at night. It was lowered so much my high beams were lower than the lows on the 89.

Siggie thanks for the input, Basically I think we agree a stock 5.2 is a better choice than a rodded 3.9.