Engine Swap

  • 3.9L
  • V6
  • 4WD
  • 170,000 MILES
I plan on doing an engine swap on my Dakota and need some answers please. I've been to a lot of different forums and looked up different thing but still have questions. I found a 1992 318 magnum for my 1999 Dakota sport 4x4 I plan on using the same transmission which is an automatic. I know I'll need a flex plate and a pcm with a harness but would like to use my same wire harness but add two injector connectors. I'm asking how much of a good idea this is as well as would the motor mounts from the 318 that was on a 1992 d150 fit a 1999 Dakota. Any and all thought or ideas are welcome.
Do you
have the same problem?
Monday, December 28th, 2015 AT 6:42 PM

1 Reply

If this is new to you, you can expect to put a "For Sale As Is" sign in the window. You can't just add two connectors. The injectors don't fire at the same time. They're controlled by eight individual driver circuits. The pin numbers are different so the original wiring harness will be completely different.

The transmissions are different between the two years. Besides the 5.2L transmission being beefier to handle the higher torque, the electronics are different too. You'll need an Engine Computer to match the '92 group of sensors on the engine and the '99 group of sensors and solenoids on the transmission, and there is no such computer. If you find a computer to handle the transmission, it will be looking for the signals from a bunch of sensors that aren't on the '92 engine. All '96 and newer vehicles sold in the U.S. Have the OBD2, (on-board diagnostics, version 2), emissions system. A lot of stuff is not on the '92 engine, so how are you going to handle the complaints from the computer? The Check Engine light will be on all the time, so you'll never know if a minor problem pops up that could turn into an expensive one if it's ignored. Fuel metering calculations will never be correct so there will be hesitation and stumbling problems along with poor fuel mileage.

Chrysler used to be real good about making their parts interchangeable between many years and models, which is the first reason I fell in love with the company, but I can't say for sure the transmission bell housing bolt patterns will be the same. Years ago there were three patterns; the six-cylinder, (170 and 225), the small block, (273, 318, 340, and 360), and the big block, (361, 383, 400, 440, and 426 Hemi). Engine swaps and changes were easy in the '70s and '80s, but those days are gone.

You didn't say which engine you have now, but I'm assuming you have a 3.9L. That is a 318 with two cylinders lopped off. The distributor placement, timing chain cover, and water pump were the same. Exhaust manifolds were quite different. My best guess is the engine mounts are different because they were way at the front on the 318. With the two front cylinders removed, the mounting ears have to be moved back on the block to, in effect, next to cylinders 3 and 4. If you tried to put a V-6 in place of a V-8, it would be too far forward and there would be a 6" gap between the transmission and engine block. I do know the engine mounts are totally different, but I don't know if the way they're bolted to the blocks are the same.

Look at this as an opportunity to go out and buy the truck you want. Don't try to build it on your own. For each item I told you that's different, there will be a dozen more I don't know about. I did a few swaps in the '80s for my own fun, but I'd never attempt this on the newer trucks. You also have to consider the additional weight of the 5.2L. That means stiffer coil springs or torsion bars. The carefully-designed front-to-rear brake balance will be gone. You can be sure that will be noticed when the other guy runs a red light and causes a crash. His lawyer or insurance adjuster will convince a jury that you were partly at fault because you were less able to avoid the crash, ... And he will be right. Mechanics have this in the backs of their minds all the time.
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Monday, December 28th, 2015 AT 7:50 PM

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