Engine performance upgrades.

[1991 Dakota 318]

A few years ago I tried to give her more power. I installed a k&n air filter, muffler delete, and a Jet Performance chip on it. I was somewhat satisfied with the results. It definitely had more power, but now, I kind of don?t like the torque curve. It has lots of low end torque, but not much power at the top end. Is there something I can do to change that? I think I concluded last time if I wanted to change the torque curve, I would have to do some serious mods to it. I still have to pass emissions, so I can?t just put a carb on it. I thought about converting it over to the 1992 magnum engine, but determined it would be quite a bit of work. Is there any way I can add more power by keeping the throttle body injection and still pass emissions? Or is the current upgrades I have the best I?m going to get?

[RalphP]

Remove the Jet Performance chip and you'll get your high end power back.

Past that, not much.

I'd look hard at doing the Magnum upgrade; good news, with a 1991, all you need to pick up are 1992-1995 parts and the rest should be OK.

Transmission will need to be modified or replaced (to make a place for the crank sensor); ECU is different; engine bay wiring harness is different.

If you're going whole hog, go 1996, rewire the cab also, and get OBDII so you can get the darn thing tuned to suit you easier.

(Or consider building up a LA motor, and using a carb-style EFI system; I'd bet you'd get as good if not better emissions than with a 27 year old motor!)

RwP

[1991 Dakota 318]

That?s a good thought. I will just build off of the motor I got. The truck only has 105k miles on it. I didn?t know about the aftermarket throttle body injection. Due to sitting most of its life, Every gasket and seal is leaking oil. So it?s probably time to pull it out, and mess with it. How much power can the stock drive train take? It?s got a four speed auto with an np231 transfer case and a 3.92 rear end.

[RalphP]

It'll take anything a mild build will put out; but I'd plan on rebuilding the transmission and the NP231 as you do the motor.

Actually, if you can find a 46RH to put in there, I'd do that; the 46RH is basically a 727 3 speed with lockup torque converter and OD added, and those can be handled without an ECU (PATC in Bossier City has a kit with a vacuum switch, two pressure switches, the wiring, and the proper T hoses) so that's a no-cost improvement for driving on the road IMO.

That 3.92 helps tremendously; my 1988 has a 2.92 (2.94? 2.9sumpin) and it has almost no get up and go from a standing start. (Then again it's got 375,000+ miles on it ... )

RwP

[1991 Dakota 318]

Dang, that?s a crazy amount of miles. Is it all original? Or has a lot been replaced? I know three people that have had those trucks with that high of miles.

[RalphP]

On my Dakota, motor is original save for oil pump, timing chain, harmonic balancer, and water pump. (Alternator and A/C compressor has been changed also, but they're not internal.) Oh, and freeze plugs.

The TRANSMISSION got rebuilt at about 340,000 miles this past February; it was original to that point.

And actually, for a 1988, that's only a bit over 12,000/year ... so not really that much overall. (And yes, I do about 40,000/year on it ... )

RwP

Addendum: Motor is DEFINATELY showing its age; it's overdue for a rebuilt to get the compression back up. I keep thinking about possibly going Magnum and EFI; or possibly (if I ever win the lottery! *grins* ) going to a Red Ram Hemi from the mid 50's (241/270 CID; only a couple of inches deeper than the LA 3.9; and "It's Got A Hemi!" ... )

[1991 Dakota 318]

The more I think about, magnum is probably the way to go. With an aftermarket throttle body, cam, and then getting a new transmission, I?m going to be in it for 3 grand. With the magnum, the work is mostly done for me. Just need to find a 92-95 dakota in a salvage yard, and I?m all set.

[RalphP]

For me, a freshly-built 3.9 magnum will be so much better than a 375,000 mile 3.9 LA that I wouldn't need cam, throttle body, etc.

I will need to swap transmissions, due to the Magnums using a crank sensor on the bell housing. That's not too bad; the current transmission is a 3 speed no overdrive, and if I drop in a 42RH/44RH, I can stiffen the back gear up and add even more oomph to "The light just turned, I only have 1 minute to get through the intersection!" *grins*

Plus, cruise can more likely keep 70MPH up some 10* or so hills around here (currently, WOT keeps me above 60 at the crest if I'm at 75 at the bottom starting up ... )

RwP

[1991 Dakota 318]

The transmission is all I have to worry about on the crank position sensor, aside from the wiring, right? Does the sensor on the 92+ trucks work off the cam?

[RalphP]

Originally Posted by 1991 Dakota 318

The transmission is all I have to worry about on the crank position sensor, aside from the wiring, right? Does the sensor on the 92+ trucks work off the cam?

No, the crank position sensor is on the bell housing.

Yes, they have a sensor in the distributor; that's the CAM position sensor.

(You also have to match the flexplate/torque converter so that you HAVE the teeth to pulse the crank position sensor ... )

So, again, I'm having to look at fan --> driveshaft to convert for me.

(That's if you go EFI, though; go carbed, or use a carb-mount integrated EFI like a Holley Sniper or an Atomic or any of their competitors, and the crank position sensor is no longer needed.)

RwP