Yet another 5.2 to 5.9 swap - more questions - JeepForum.com
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post #1 of 29 Old 11-15-2021, 05:10 PM Thread Starter
wn2091kc
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Yet another 5.2 to 5.9 swap - more questions

Been looking at different options to upgrade/rebuild my tired 94 5.2 and I've zero'd in on potentially swapping it for a 5.9. The overall goal here is regain reliability, maintain reasonable mpg and hopefully gain some low end grunt. I considered stroking the 5.2 but cost put it off the table for now. I've been researching the various threads on this swap topic but I still have some uncertainty. Hopefully this is not too redundant...

Best candidate 5.9 engines I found locally are currently sitting in:
02 Ram 1500 (engine looks in decent shape and turns over, vehicle body damage so assume that's why it was junked)
01 Durango R/T (vehicle and engine look in decent shape with no body damage; engine turns over; not clear why junked...)

Both have 200-250k miles. I plan to do a full teardown regardless (I'm retired so time/effort is not a concern; money is however) and machine as needed. Maybe swap in a new mild cam. It seems that looking on various parts sites, there is a breakpoint in parts fitment between 1998 and 1999 model years that may impact me. So ... I'm wondering about unforeseen issues with swapping to a post-98 5.9 engine.

My plan is to:
- use the 5.9 short block; tank it, bore (if needed), hone; new bearings, rings, seals, timing set, etc
- prob new mild cam but wondering about the cam in the Durango R/T which I believe is the mopar performance cam from that year (may be worn out anyway)
- use my existing OBD1 ECU
- use my existing 5.2 beer keg intake, TB, sensors, EGR and injectors
- use existing 5.2 exh manifolds and pipes
- will use better of 5.2 or 5.9 heads and do full valve job either way
- use my existing 46RH trany and torq conv
- use the 5.9 flexplate and harmonic balancer
- use my existing starter from the 5.2 (5.9's seem to usually mount on the drivers side but I think it will still mount on the passenger side of the 5.9)
- use my 5.2 crank sensor but I'm not sure it will fit (part numbers are diff for 94 5.2 and 01/02 5.9)

So, are there any other considerations, serious holes or showstoppers in this approach?


94 ZJ Laredo 5.2 Magnum
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post #2 of 29 Old 11-15-2021, 06:32 PM
kg6mov
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The durango r/t didn't have the mopar performance cam from the factory.

As I understand it you've got it correct for the swap. Include the fuel rail in with intake and injectors of course, 94 was the last year of reg on rail.


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post #3 of 29 Old 11-15-2021, 08:23 PM
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I doubt the block was changed throughout the years, so wondering what the fitment issues might be.
The left motor mount is block specific.

Sounds like you got it. Be careful with the cam choice since you can't do any tuning. I *read* on one of the Dodge forums that a later 5.2 cam might give you a little more power in a 5.9.
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post #4 of 29 Old 11-15-2021, 08:31 PM Thread Starter
wn2091kc
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Quote:
Originally Posted by kg6mov View Post
The durango r/t didn't have the mopar performance cam from the factory.

As I understand it you've got it correct for the swap. Include the fuel rail in with intake and injectors of course, 94 was the last year of reg on rail.

K, thx on the R/T cam. Will assume it is stock. What lead me to assume that is I found a dodge dealer sticker under the hood that said something to the effect that the ECU was re-programmed with the performance mod. I assumed that include the performance cam but as you suggest was separate and distinct from any hardware changes to the engine.

And yes, I will be keeping the 5.2 fuel rail...

94 ZJ Laredo 5.2 Magnum
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post #5 of 29 Old 11-15-2021, 08:36 PM Thread Starter
wn2091kc
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Quote:
Originally Posted by HighLonesome View Post
I doubt the block was changed throughout the years, so wondering what the fitment issues might be.
The left motor mount is block specific.

Sounds like you got it. Be careful with the cam choice since you can't do any tuning. I *read* on one of the Dodge forums that a later 5.2 cam might give you a little more power in a 5.9.

Thx for that. Hmmmm... I was thinking something like a Compcams mild cam would be my best bet if I need to swap out the existing cam in the 5.9 block. I'll dig into that further and see what info I can find.

94 ZJ Laredo 5.2 Magnum
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post #6 of 29 Old 11-16-2021, 08:20 AM
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Starter doesn't mount to the engine so that's not a problem.


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post #7 of 29 Old 11-16-2021, 09:37 AM Thread Starter
wn2091kc
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Starter doesn't mount to the engine so that's not a problem.

Ya, I realize that now.

94 ZJ Laredo 5.2 Magnum
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post #8 of 29 Old 11-16-2021, 03:02 PM
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Been a long time since I've thought about a 5.9 conversion in an OBD1 ZJ but this much I remember.. The stock PCM did not yield very good results. I had a number of people doing swaps call me and tell me of power/driveability issues and what always resolved them was the Mopar Performance PCM. Of course, that's long ago discontinued so I'd suggest you begin to search for a good used one.

B&G used to program OBD1 PCMs but they've been telling everyone I send to them "no" lately.

Does anyone know of anyone else out there that's still willing to program OBD1?

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Member: Specialty Equipment Market Association
Telephone: 480 998-3661

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post #9 of 29 Old 11-17-2021, 11:16 AM Thread Starter
wn2091kc
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Quote:
Originally Posted by Kolak View Post
Been a long time since I've thought about a 5.9 conversion in an OBD1 ZJ but this much I remember.. The stock PCM did not yield very good results. I had a number of people doing swaps call me and tell me of power/driveability issues and what always resolved them was the Mopar Performance PCM. Of course, that's long ago discontinued so I'd suggest you begin to search for a good used one.

B&G used to program OBD1 PCMs but they've been telling everyone I send to them "no" lately.

Does anyone know of anyone else out there that's still willing to program OBD1?
Kolak, yes, there still remains some resources to help program an OBD1 PCM. I connected with [email protected] (thanks to forum member tetatdo for that pointer) and he indicated the other week that he can still program one although I have not pursued that matter further so far.

You indicated above you did not obtain very good results. Can you elaborate on that further? Did you do other mods to the 5.9? Was it worse performance? The same? Only slightly better? Not sure what your expectations were in that case.

Thanks.

94 ZJ Laredo 5.2 Magnum
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post #10 of 29 Old 11-18-2021, 03:06 AM
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Thanks for mentioning Chris! I will put his contact info into my file so I can recommend him to people.

The fuel and spark tables for the 5.2 PCM are not optimal for the larger 5.9 V8. What customers typically noted was all sorts of symptoms including detonation/spark knock, low speed stumbling and hesitation as well as high speed/full throttle mode surging. Power gains were also perceived to be not what they should be considering the displacement increase.

Back then the Mopar Performance PCM was a great choice and largely resolved the issues. But I expect a custom tune from Chris would be even better.


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Originally Posted by wn2091kc View Post
Kolak, yes, there still remains some resources to help program an OBD1 PCM. I connected with [email protected] (thanks to forum member tetatdo for that pointer) and he indicated the other week that he can still program one although I have not pursued that matter further so far.

You indicated above you did not obtain very good results. Can you elaborate on that further? Did you do other mods to the 5.9? Was it worse performance? The same? Only slightly better? Not sure what your expectations were in that case.

Thanks.

Kolak Performance and Offroad
Member: Specialty Equipment Market Association
Telephone: 480 998-3661

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post #11 of 29 Old 11-18-2021, 12:55 PM
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Quote:
Originally Posted by Kolak View Post
Thanks for mentioning Chris! I will put his contact info into my file so I can recommend him to people.

The fuel and spark tables for the 5.2 PCM are not optimal for the larger 5.9 V8. What customers typically noted was all sorts of symptoms including detonation/spark knock, low speed stumbling and hesitation as well as high speed/full throttle mode surging. Power gains were also perceived to be not what they should be considering the displacement increase.

Back then the Mopar Performance PCM was a great choice and largely resolved the issues. But I expect a custom tune from Chris would be even better.
Is this a problem only with the OBD 1 system or all years of the ZJ?
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post #12 of 29 Old 11-18-2021, 02:12 PM
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All years would require PCM tuning, but 1996 and later OBD2 PCMs are flash programmable and there's lots of options for getting a custom tune done, such as SCT.

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Is this a problem only with the OBD 1 system or all years of the ZJ?

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post #13 of 29 Old 11-18-2021, 03:12 PM
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Just remembered, you'll need a torque converter for '96 V8 and up to match the 5.9 symmetrical flexplate. '93 - early '95 V8 has an asymmetrical flexplate/torque converter.
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post #14 of 29 Old 11-18-2021, 03:48 PM
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Nah, the converter is neutral balanced so there's no issue just drilling the flexplate to accept the offset pattern.

Stock computer in my 96 runs the 5.9 just fine. The flash from flyinryan is peppier, but the factory 5.2 flash seems to be just as drivable. OBD1 is a different beast of course.


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Quote:
Originally Posted by Texas ZJ1 View Post
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post #15 of 29 Old 11-18-2021, 05:29 PM
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I got my wires crossed in my post and fixed it. '93-95 is asymmetrical.

When I did a swap on my '94 I drilled the symmetrical 5.9 flexplate to match up to the asymmetrical 5.2 torque converter. But then I got to reading that it might affect engine balance, so I put in a new 5.9 flexplate and torque converter. It ran fine with the drilled flexplate, but I couldn't relax just knowing.

For my late '95, I was happily surprised when I found an OEM symmetrical flexplate and torque converter. Still need the balanced 5.9 flexplate though.

My '95 is running nice. Perfect idle. A lot more torque than the 5.2, but runs rich at low RPMs it seems. Always smelling fuel offroad with the windows down. My other '95 with a 5.2 doesn't seem to do this. Just for grins, I popped the Mopar performance computer in the 5.9 swap last night. Drove around town a little and didn't notice much difference, but it needs time to learn I guess.
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