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 Post subject: No Budget tbi from 3.9L
PostPosted: Thu Dec 07, 2017 4:35 am 
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2 BBL ''SuperSix''
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Hi everyone.
I have a question about using 3.9L V6 TBI from a 1988 D150 (that I already have for parts and only cost me $50) and swapping it to my 1987 D150 /6. Everything is there for an easy swap and it will all fit as almost everything but the engines are the same. Fuel tank with fuel pump, return line, even the computer under the right fender all look similar in shape and mounting. The TBI only has a few vacuum lines and wires that may even cross to the /6 wiring without to much trouble as the two trucks are only 6 months apart from each others build date. I realize I might have to install some sensors from the new to the old but that should not be to complicated. I have almost Zero funds to put into this as I spend most everything on a 440, but thought I might get better mileage and maybe a little more performance out of my fishing truck.
Am I biting off more than I should or is this going to be a bad thing to try? Remember, I don't have hundreds or thousands to spend but I have all the tools, I'm great with wiring and electrical, Been building engines since my Dad let me clean the dirty car parts for him!
P.S. First time experimenting with TBI!
Thanks for any info or ideas I can get.

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PostPosted: Thu Dec 07, 2017 6:15 am 
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It sounds like a cool project. It is definitely doable!

If you go to the Home page (link on the top next to Forum Index) and go to the Articles section there are a couple good articles on swapping over to fuel injection. That will be a good start. Once you've read through those you can ask some more specific questions.

When I lived near Flagstaff (Camp Navajo) I bought a '71 Sweptline from Kingman. I towed it home on a car dolly behind my Dodge Caravan... :shock:

Good luck with your project.

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PostPosted: Thu Dec 07, 2017 9:07 am 
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Sounds like a cool swap. The computer that runs the TBI is probably the biggest unknown, and it might be good to just swap the whole wiring harness from the '88 truck. Should be a nice match for the /6.

Lou

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PostPosted: Thu Dec 07, 2017 11:18 am 
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A guy on FABO did a few V8 kits using the later TBI. Several people asked about a slant conversion. He said he needed a slant distributor w/o a vacuum advance to convert using the 3.9 dizzy internals since they are not the same. I sent him one I had. After several inquiries by me and others, he claimed he had it converted and running in a slant But it all needed “prettying” up all the wires to the computer and motor. After replying to one email from me offering to be the the end user tester, he dropped out of sight. Never heard from him again. Good luck on trying a conversion!

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PostPosted: Thu Dec 07, 2017 11:29 am 
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This is going to be more complicated than it might seem, and the TBI system we're talking about is a poor one (though maybe somewhat less awful than the strangled late-production Slant-6 carburetors). You will have to custom-build a distributor with a Hall Effect pickup, and you may run into difficulties there. You'll need all of the sensors, solenoids, and actuators to be in place and working, and you'll want to swap on a transducer-type EGR valve (that's this one). Good luck on it, and lettuce know how you get along!

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PostPosted: Thu Dec 07, 2017 12:12 pm 
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Ah, I forgot about the hall effect dist pickup. That's an important point, but should be surmountable. I always have used MegaSquirt EFI and customized everything....

Lou

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PostPosted: Thu Dec 07, 2017 1:43 pm 
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Another thing to keep in mind is that the OE Mopar system controls ignition and the fuel. I thought the Mopar distributors were the same size around. If so, the V-6 guts should fit in the slant 6 distributor. I am not sure if the TBI setup uses a crank sensor. That could be a problem as well.

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PostPosted: Thu Dec 07, 2017 3:52 pm 
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My memory of that pathetic TBI system is fading faster than I had a right to hope, but I seem to recall there is something about the difference in distributor event spacing (in degrees) that makes the V6 Hall effect sensor not usable with the Slant-6. I think custom parts would have to be made.

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PostPosted: Thu Dec 07, 2017 4:59 pm 
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Quote:
I seem to recall there is something about the difference in distributor event spacing (in degrees) that makes the V6 Hall effect sensor not usable with the Slant-6.


At some point the Mopar 3.9L was an Odd fire instead of an even fire engine like the slant... did they start that way or was the switch in the early 90's when MPFI finally took hold?


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PostPosted: Thu Dec 07, 2017 5:02 pm 
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Yeah, now you mention it, I think that was/is the issue: odd-fire on the carbureted and TBI 3.9 V6. Don't know if it stayed that way after the '92 Magnum redesign, but it doesn't matter to the question at hand.

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PostPosted: Thu Dec 07, 2017 8:36 pm 
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Don't know if it stayed that way after the '92 Magnum redesign, but it doesn't matter to the question at hand.


He'd have to pull a magnum dizzy at the junkyard... if it was even fire (I know the 5.2 magnum had even spacing on it's trigger star).

I do know that the Magnum 5.2L dizzy body is slightly different than the EI/ESC dizzy and shaft height is shorter...but... if the 1992+ 3.9 magnum
has the even fire spacing (I don't think it does)... I know the 5.2L magnum body should fit the slant six dizzy hole... so changing the star and "guts", then indexing
the dizzy in a dummy block with camshaft installed, he could figure out where to mount the gear, then have a machinist lathe off the rest of the
shaft and redrill the shaft for the gear hole....

I have mocked this up with a big block dizzy in a slant six block, using a 1979+ claw style hold down....(was working on the idea of having the dizzy higher
so on the fly spring changes would be easier without pulling the dizzy and having to reindex it....which it did get it up to the level of the spark plugs where
you could see and play with the guts... but still not as easy as I would imagine as doing the change on the bench anyway... and would barely work due to fender location for late-A, B, C, E, and FMJ bodies due to the wider engine bay)...

The next problem I would forsee, is the size of the magnum "body/"cup" is a little wider than the EI dizzy (kind of similar to the HEI GM dizzy)... so that might put the
dizzy too close for comfort at the head and adjoining spark plugs....


But again this is academic as this is not going to be a "no or lo buck mod"....even finding an even fire other brand hall effect distributor then trying to adapt the guts
to an ESC/EI or Magnum dizzy might not be a no-lo buck option either....


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PostPosted: Thu Dec 07, 2017 11:17 pm 
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Car Model*: 1973&84 Sportsman,1987&88 D150
Wow, The wealth of information and ideas here is amazing and very appreciated. I must admit that this does not seem to be a easy or a low buck idea. I have read that there are major differences in the timing of the v6 and the /6, and distributors would not be a even swap or even a light modification.
But I also noticed that my 87 has a ESA and so does the 88. Are these similar in function for timing and fuel. The ESA's seem to be almost Identical except more wires for sensors and the TBI on 88. I thought that maybe the original distributor that supplies the signal to the ESA for the 87 would work for the 88 ESA? I don't see any type of mass air flow sensors on the air cleaner or between the ESA and the TBI or any other differences on either one. they both connect the same way to the air cleaners. If it is incorporated in the ESA, couldn't the original 87 distributor combined with the 88 ESA and 88 wiring harness work together? These trucks could have been in the same parking lot at the factory, they are so close in their B-days.
Some one mentioned vacuum advance, neither truck has it. distributors have leads coming out to ESA.
Thanks again everyone!

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PostPosted: Thu Dec 07, 2017 11:26 pm 
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2 BBL ''SuperSix''
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I also read in this forum that the ESA controls electronically the lock-up torque converter. Changing to any other ignition system would probably lose this function.

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PostPosted: Thu Dec 07, 2017 11:52 pm 
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azclpherigo wrote:
my 87 has a ESA and so does the 88. Are these similar in function for timing and fuel. The ESA's seem to be almost Identical except more wires for sensors and the TBI on 88. I thought that maybe the original distributor that supplies the signal to the ESA for the 87 would work for the 88 ESA?


No, not a chance.

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PostPosted: Fri Dec 08, 2017 5:14 pm 
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Never in a million years would I try to fit the odd-fire ECU from the 3.9 to a 225. The crank pins on the 3.9 are only split 22 degrees so the bank-to-bank firing intervals are off by 8 degrees. This is true of every 3.9 AFAIK and I've examined both TBI and Magnum versions. If you look at the back of a Magnum 3.9 flywheel you can see pairs of notches on the back for the crank position sensor. If it were even fire it would have single notches like a V8 flywheel.

The Buick hardware that's been adapted in the past came from even fire engines and also used the more forgiving mass airflow sensing system. Speed density systems are not forgiving of differing volumetric efficiencies.

If you're going to use TBI at least use a computer that's been hacked like a common GM one. But you're probably money ahead going with Microsquirt. https://www.diyautotune.com/product/mic ... g-harness/ Yes, it's $400, but it will work and you can tune it. As you will never be able to get the timing right or otherwise tune the Dodge ECU it's worth it to go aftermarket.

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