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Hi guys, I'm new to this forum and would like some advice about the engine swap that will be getting done for my subaru pretty soon. I have a 2002 outback base 2.5l that I was pretty sure was a dohc when I first got it, and I havent checked the VIN yet to make sure since the car is at storage. Here is the question though, what would need to be done to make a DOHC work for a car that had a SOHC in it, because the engine is already on its way and it would cost way too much to send it back and get a new one. The engine I have coming is a 2005 ej254 DOHC 2.5l 16 valve with only about 65K miles on it, the engine block for my old engine is completely siezed up so replacing it is the only good option for me at this point, ill just scrap the old one or give it to someone who has the time to tinker with it. Any information would be very helpful , thanks.

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to some extent DOHC and SOHC doesn't tell us anything.  some DOHC and SOHC engines are plug and play interchangeable.  some DOHC and SOHC engines are not....so you need to tell us exactly what motor you're getting - not just DOHC or SOHC, that's meaningless at this point....

 

what exactly did you buy and why did you purposefully buy the wrong motor?

 

a DOHC TURBO engine for your non-turbo vehicle?
a DOHC JDM engine for your USDM vehicle?

 

year, make, model, turbo/non turbo..JDM, USDM....

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My car is just a base 2002 subaru outback, non-turbo all stock, I got the engine from JDM and here is the description they have for it:

JDM 01-03 SUBARU LEGACY / OUTBACK / FORESTER / IMPREZA 
 

EJ254

2.5L DOHC 16-VALVE ENGINE

!!! IMPORTED DIRECTLY FROM JAPAN !!!


THE ENGINE WE HAVE IN STOCK WAS REMOVED FROM A THE JDM SUBARU LEGACY / OUTBACK / IMPREZA / FORESTER IN JAPAN AND IMPORTED DIRECTLY TO US WITH APPROXIMATELY 45K-65K MILES ON IT!


***NOTE: THESE ENGINES DO NOT RUN AN EGR SYSTEM THEREFORE PLEASE CHECK WITH YOUR MECHANIC ON HOW TO BYPASS IT. YOU MAY OR MAY NOT NEED TO SWAP OUT YOUR EXISTING INTAKE MANIFOLD. PLEASE VERIFY THIS WITH YOUR MECHANIC PRIOR TO PLACING YOUR ORDER. ***
I didnt purposefully buy the wrong engine i looked up the compatibility for engines for my year of car and it said that the ej254 was compatible with the 2002 outback, only after I placed the order did i decide to look up the specs for the 2002 subaru and found that all the standard engines that were with the 2002 were single overhead cam, when i was pretty sure my car was dual over head cam, i will be stoping by my car today to check on the VIN and make sure what engine it is.
 

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a 2005 ej254 DOHC 2.5l 16 valve

 

yeah, wrong engine.

 

it may run if you swap in your intake manifold, cam & crank sprockets.

but i don't KNOW any one who has done it so it may not.

 

i don't really think the ECU is going to care about the number of cams,

but if any of the sensors are different, (cam, crank, temp, TPS, IAC ?????) and they probably are,

it could create wiring issues trying to get it to work.

 

other options at this point ,

use the block and bolt on your heads, intake, and sprockets.

 

sell this engine and buy the right one.

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DOHC and SOHC doesn't really matter in itself.

 

here's what you would do:

 

bolt the original SOHC intake manifold onto the DOHC engine.

if any sensors (cam, crank, knock, temp) have different connectors - just swap them out - SOHC in place of the DOHC ones.

use your original SOHC igniter, coil, etc, you basically only want to swap the bare block/heads/cams, that's it.

 

*** here's the only unknown you need to figure out (but this company probably knows this swap is possible, right, surely they've been asked):

 

trigger points - the drivers side cam (top most cam for the DOHC) and crank sprocket have trigger points on them for the sensors, they need to be the same as the original engine.

 

1.  first step is to simply remove and compare (or ask, google, search part numbers, pictures).  if the cam sprockets have the same spacing/number of triggers then you're golden.  install the engine as said and you're done.

 

2.  if they are different then:

install your SOHC crank sprocket on the DOHC engine, those should easily interchange, they just pull off and on by hand and cranks are identical.

*** Here's the only thing I'm unsure of if you can do it or not - install your SOHC drivers side cam sprocket onto the DOHC engine

 

3.  another alternative that will work for sure is to just bolt the SOHC to the DOHC block, then there's no cam worries since it's the same cam sensor/sprocket/triggers the ECU is looking for. 

 

could even swap just one side, drivers side to SOHC and leave the other DOHC but probably only me and a handful of others would do that, everyone else would poo themselves, LOL

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