After looking up the following it shouldn't be too hard to do the swap. However, the 95 is the least compatible of the first gen neons and you might encounter some wiring problems. As far as bolting down everything *should* fit but expect some fine tuning and you might have to rig some custom wiring. If you end up having to do this, I'd suggest getting full manuals with detailed wiring diagrams. Refer to the following for a list of possible problems and considerations.
If you want to swap your SOHC (single over head cam) engine out for a DOHC (dual over head cam) engine, this is the information that you need. I am writing this with the idea that the person reading it knows enough about internal combustion engines and has enough mechanical inclination to attempt the project. (However this will pretty much work for a DOHC to SOHC swap as well )
1. What are the Differences between the SOHC and the DOHC?
The differences between these two engines are primarily in their cylinder heads.
The DOHC (ECC) has two camshafts inside the head. One camshaft opens and closes the intake valves, allowing air and fuel into the combustion chamber. The other set operates the exhaust valves, allowing exhaust gasses to flow out of the combustion chamber after the air and fuel mixture is burned.
The SOHC (ECB) engine has only one cam, which opens and closes both the intake and exhaust valves.
Both heads have the same number of valves (16.)
The compression is also different between DOHC and SOHC engines, because the pistons are slightly different. The DOHC has a raised piston dome with 4 valve reliefs. While the SOHC has a flat top pistons.
The DOHC engine has a rev limiter of 7200 RPM.
The SOHC engine has a rev limiter of 6750 RPM.
The 2.0 DOHC engine is rated from the factory with 150 hp @ 6500 RPM with 133 ft/lbs. @ 5600 RPM of torque
The 2.0 SOHC engine is rated from the factory with 132 hp @ 6000 RPM with 129 ft/lbs. @ 5000 RPM of torque (NOTE: This SOHC rating is for m/y 96-99 due to 95 m/y having a slightly hotter cam)
The compression ratio of the stock motors are
9.6:1 for DOHC
9.8:1 for SOHC
9.3:1 for California controlled SOHC also know as the TLVE
You can get creative and swap a SOHC head on a block that has DOHC pistons and it will yield a compression ratio of 10.3:1 (more compression = more power)
You can swap a DOHC head on a block that has SOHC pistons and it will yield a compression ratio of 9.3:1
Other differences between the complete DOHC and SOHC motor assemblies are
Both intake and exhaust manifolds are different they will not swap over.
(SOHC motors have two versions of the intake manifold, Plastic and Aluminum)
The fuel rails are also different between the SOHC and DOHC.
While both the SOHC and DOHC motors have 19lb injectors, they are different. The DOHC injectors are longer and will not fit a SOHC without some modification same goes for using such injectors on a DOHC.
I am not getting into gear ratio differences on the transmissions here. I am simply talking about the engines. The most important thing is that all 1995-1999 neon transmissions are interchangeable. Automatics and manuals.
2. What parts do I need to complete the SOHC to DOHC swap?
Read the details on each item, to ensure that you need it.
You will need:
I. DOHC engine (complete)
* Intake manifold
* Exhaust manifold
* Proper injectors and fuel rail (read above)
On a side note:
1995 m/y Neons have separate IAT and MAP sensors and the intake manifold has provisions for both sensors.
1996 1999 m/y Neon s have an intergraded IAT/MAP sensor requiring only one hole in the intake manifold.
On 1996 1999 m/y Neon s it is possible to use the 95 manifold however it will take some modification.
On 1995 m/y Neon s you will not be able to use a 96 99 intake manifold.
II. DOHC PCM of the same year as your car
Read the information under DOHC Wiring Harness
III. DOHC Wiring Harness
Make sure the wiring harness will work with your car. If you have a 96+ engine, you need a 96+ harness.
To convert a SOHC harness to DOHC, you need to change the cam positioning sensor plug, and extend the coolant temp sensor plug, it needs to be long enough to reach passenger front side of the head. Sensors may not be plug and play. You may need to buy new sensors for certain applications or use the sensor form your other motor.
If swapping DOHC to SOHC the harness will be long enough to reach.
There are some differences to some of the harnesses depending on the year:
(early 97 wiring harnesses are odd, they may have differences such as VSS, alternator, brown wire that goes to the starter, TPS, and the IAC motor all have different plugs. From what I can gather it is a Frankenstein harness between the 96 harnesses and late 97-99 harness s)
1995 PCM has a single plug that connects to the frame, motor, and cabin wiring harness.
1996-1999 PCM has two plugs that connect to the frame, motor, and cabin wiring harness.
1995 model year has unique plugs for almost all the sensors in the engine bay.
1996 model year is a hybrid between 95 sensors and 97-99
1997 - 1999 No changes were made to the wiring harness between these years. Use all the same sensors.
1995 has a separate MAP and IAT sensor.
1996-1999 have an integrated MAP / IAT sensor.
1995-1996 use the PDC for the fan relay.
1997-1999 use a separate fan relay located just below the driver side headlight.
1995-1997 use Bosch plugs for the injectors.
1997-1999 use the USCAR square plug
The plug change happened mid year so some 97's have Bosch style some have the USCAR style.
1995-1997 use the same alternator and starter.
1998-1999 use the same alternator and starter.
They only fit the correct years harness.
IV. DOHC Motor Mounts
There are two different types of motor mounts. They are: steel and aluminum. The steel mounts are interchangeable; the aluminum mounts will only work on the motor they came off of. If you have the aluminum mounts, you will need to buy new motor mounts.
3. Is it worth it to swap from a SOHC to a DOHC?
If you happen to have an extra DOHC engine, or got one really cheap, then you may find this swap worthwhile. If you plan on continuing to modify your car with a turbo, or other performance parts then you may find this swap worthwhile. If you simply want to change your engine out to gain this horsepower and do no more, then you are better off to spend your money or some parts for your SOHC engine and enjoy them. Different people have different opinions of these engines and this process.
4. Is the 420a engine from an eclipse the same as the neon DOHC?
No. The DOHC Neon (ECC) shares a cylinder head with the 2.4 DOHC engine found in the 1st gen stratus, etc. They are the exact same casting number. The Avenger/Sebring/Eclipse 2.0 DOHC (420a) head is unique and has reversed flow; although, a few parts from the 420a will work on the ECC. For instance: The 420a valve cover has unique raised lettering reading "DOHC 2.0L 16 valve" and can be swapped onto an ECC.
Saturday, April 5th, 2008 AT 5:35 AM