DOHC swap to SOHC
Veteran
Joined: Apr 2004
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From: Elk Ridge, UT
Uh...the PCM will DEFINITELY not be a problem. I ran a performance DOHC on my 95 SOHC for two years without any problem. your stock mopar dohc PCM will raise the rpm limiter and fueling and spark maps are different than a SOHC but day to day not a big issue. In fact, during those two years I also was running a crane #2 cam on my SOHC and the emissions were actually lower than any previous year (but of course had lower mileage) and were at like 1/10th the allowable.
a stock DOHC pcm isn't going to overly enrichen your SOHC.
however, you do need to make sure you have same year sensores (or reuse from your DOHC).
a stock DOHC pcm isn't going to overly enrichen your SOHC.
however, you do need to make sure you have same year sensores (or reuse from your DOHC).
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Registered User
Joined: Sep 2008
Posts: 14
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Well that would make it a whole lot easier if I could simply take the dohc engine out and replace it with a sohc complete engine! I don't care about horsepower, smok'in the tires or anything like that! This is a hack car and I'm more interested in mpg than anything! So your saying I can swap engines and use my existing dohc pcm with no problems? It also sounds like your saying the sensors on the dohc engine will fit on the sohc engine therefore the wiring harness will not require modifications???
Veteran
Joined: Apr 2004
Posts: 397
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From: Elk Ridge, UT
Oh.. there might a be a couple swaps/splices you might have to do.
For instance when I put a 96 sohc in my 95 sohc car I think the cam sensor was different. The speed sensors on trannies are different. And of course the terminal for the coil is different.
But if you go get a good running SOHC (assuming you don't want to rebuild to save money too...but consider that putting in a new MLS head gasket while you've got apart is a good idea anyway) then you'll have all the parts you need side by side from your old block. Use your DOHC coil (but get the SOHC bracket with the engine when you go get one...or I may have an extra laying around) etc.
The nice thing with the SOHC and a 3.94 sport tranny was that even though the SOHC isn't making 150 horse it's still kinda nice to rev up a little quicker--I used that for about 3 years.
The only thing about the 3.94 tranny is that you'll be turning something like 3300 or 3400 at 75 to 80....got very buzzy. Also takes it beyond the MPG threshold on my sohc setup anyway...so if you're really looking for mileage you might consider swaping in a 3.55 SOHC manual tranny instead. With the 3.94 my commute got me between 32 and 36 (depending on how I was driving...how fast) and with the current 3.55 and a little more CR that I use I'm regularly getting 41 MPG...with a stock SOHC computer of course.
remember too that if you decide you want the safety of the lower RPM limiter in the SOHC computer and/or you decide you don't like the tuning (with DOHC you get better performance out of higher octane but with SOHC it mostly adjusts with knock sensor and so it doesn't help to run premium...although midgrade has earned me a little better mileage with repeated use) THEN you can swap the computer if you use the same year PCM and you DO NOT have to swap the wiring. You can usually get a SOHC computer from Ebay (stock) pretty darn cheap.
For instance when I put a 96 sohc in my 95 sohc car I think the cam sensor was different. The speed sensors on trannies are different. And of course the terminal for the coil is different.
But if you go get a good running SOHC (assuming you don't want to rebuild to save money too...but consider that putting in a new MLS head gasket while you've got apart is a good idea anyway) then you'll have all the parts you need side by side from your old block. Use your DOHC coil (but get the SOHC bracket with the engine when you go get one...or I may have an extra laying around) etc.
The nice thing with the SOHC and a 3.94 sport tranny was that even though the SOHC isn't making 150 horse it's still kinda nice to rev up a little quicker--I used that for about 3 years.
The only thing about the 3.94 tranny is that you'll be turning something like 3300 or 3400 at 75 to 80....got very buzzy. Also takes it beyond the MPG threshold on my sohc setup anyway...so if you're really looking for mileage you might consider swaping in a 3.55 SOHC manual tranny instead. With the 3.94 my commute got me between 32 and 36 (depending on how I was driving...how fast) and with the current 3.55 and a little more CR that I use I'm regularly getting 41 MPG...with a stock SOHC computer of course.
remember too that if you decide you want the safety of the lower RPM limiter in the SOHC computer and/or you decide you don't like the tuning (with DOHC you get better performance out of higher octane but with SOHC it mostly adjusts with knock sensor and so it doesn't help to run premium...although midgrade has earned me a little better mileage with repeated use) THEN you can swap the computer if you use the same year PCM and you DO NOT have to swap the wiring. You can usually get a SOHC computer from Ebay (stock) pretty darn cheap.
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Joined: Aug 2007
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From: roswell New Mexico