Hi All,
I"m new to the forum and I'm looking for information on
removing the ECM and replacing the Distributor and installing an old points type system. I know I will have to replace the throttle body with a two barrel carb. Any advice or information would be greatly appreciated.


1989 Dodge Dakota LE
3.9 L V-6
5-speed Auto trans with OD
102k miles.
Cat Bypass system

 

Not sure but what is a "cat bypass system"?

 

You will have several things to overcome with this conversion. And keep in mind these are my opinions so take them as just that. Also want to point out I was going to try something very similar myself at one time, so again, I am just sharing information I have gathered.


As you may know, the 3.9 V6 is basically a 5.2 V8 with 2 cylinders cut off.
That being said here is a list of problems I see with this conversion.


1. Distributor, The cylinder timing is not set at 120 degrees, equally around the distributor like the older slant 6 engines. The cylinder timing is 124 then 116 degrees etc. At one time, Mopar offered a performance distributor but it has not been available for years. The best I could tell, no one makes any aftermarket distributor that will work with the 3.9 motor. And again, there is no factory distributor available other then what you have.
2. Carb. I don't think that would be that bad. The 87 used a 6280 series holley 2 bbl. which is a feedback carb based on the 2280 series. Long story short, I believe you could get a 2280 off of a older 318 and then of course you would need to tune it for the smaller motor.
3. Not sure if you will have any problems with adapting a carb to your throttle body intake, but if so, you could always pick up a 87 intake. It was carbed that year.


For myself, eventually I plan to buy a complete 5.2 or maybe 5.9 magnum motor. Carb intakes are available from pro products or edelbrock. Then for ignition a standard 318 distributor or electronic ignition distributor drops right in. The magnum motor will bolt right in to your existing motor mounts. The main problem to overcome is clearance between the engine and radiator. This can be solved (as the Shelby Dakota's did) by using an electric fan in front of the radiator thus eliminating the mechanical fan.


Good luck and let us know how it goes!!

 

There is, of course, the in between - use the original (or a reman'ed!) distributor with an electronic ignition box.

That would take care of the "No points style distributors for your truck!" problem.

RwP

 

Ralph, the 87 and forward distributor runs off of the computer that also controls the feedback carb. (on the 87) What kind of box would you use with the oem distributor that would allow it to be a stand alone system?

 

Old wanderer here checking back in, I've done this on my '91(RIP).
I composed a nice long reply but the forum lost it, always click 'remember me'
Unless life gets in the way I'll check in tomorrow with pix of how how I pulled it off.

 

After doing a little more reading on this subject I found reference to the firing being at 112 and 128 degrees. So it is even worse then I posted above.
I don't think you will ever find a points style distributor that will fire at the 112-128 degree which the v6 requires to run as designed. (correctly) A 6 cyl slant 6 is going to be at 120 degrees all the way around.
Now if you could somehow adapt the reluctor out of a v6 (112-128 spacing) into a v8 distributor and then use the v6 cap, it should work.
To do this, I believe will require some machine work.
Would really like to hear from someone who has done this and got it to work correctly.

 

Well, MSD (My Spark Disappeared) makes a box that a) supports using the factory pickup, b) supports uneven-fire V6s, and c) includes instructions on how to connect to a Mopar distributor.

http://www.msdignition.com/uploadedF...structions.pdf

Edit: Checking on Allpar.COM, I find where there's instructions on how to use the stand-alone electronic ignition module from older Mopar products, or a GM HEI module, with a LA reluctor-style distributor. They talk V8, but the dang ignition module doesn't care, it fires off each pulse from the reluctor!

http://www.allpar.com/fix/electronic-ignition.html

RwP

 

Now this is more what I had in mind. Again, the main problem would be a reluctor wheel to fire the uneven v6 motor. I have heard that it is possible to machine the orig. v6 reluctor wheel or v8 dist. to mate the two together. I would love to hear from someone who has actually done it.
FWIW I understand the slant 6 reluctor wheel fits the v8 distributor, and it may run. I find it hard to believe it runs right!! With the spacing being 120 degrees, and the v6 design being 112 and 128. I believe its going to fire one cyl 8 degrees early and the next 8 degrees late.
If I am missing something here, I would appreciate further information on this subject.

 

Umm ... the Allpar instructions included using the old factory reluctor.

A bit more time with Google, and I turned up several units like the Stealth Black Box, http://www.accuspark.co.uk/Blackbox.htm .

There's also the possibility of using a MegaSpark or some other "EFI" control that's been stripped down to just ignition control.

RwP