Author Topic: Gen 2 / 2.5 Mivec Swap + 3.8 Swap info  (Read 6691 times)


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Gen 2 / 2.5 Mivec Swap + 3.8 Swap info
« on: November 12, 2017, 10:55:36 PM »
Mivec Swap info + Non Mivec 3.8

This is information that has been compiled by not just me but others. ChargerX3 and Dwight (Not sure of his handle on here). Thanks to Ernest and Toasty for being sounding boards and all your input. Info will be updated and added as new things come to light.

So you are wondering why people are talking about or doing this swap.. It's all about power. While the 3.8 Mivec is not a power house like 4g63 or 2Jz TT, LS7.. It is huge drop in upgrade to our off road rigs that requires very little fabrication and keeps the cost fairly low. Parts can be purchased locally or any dealer.  They make over 280hp to the wheels with just a couple mods and no tuning. So going from 195Hp at the crank to over 280 to the wheels is a huge upgrade.

Non Mivec 3.8 - These motors can be found in a ton of FWD cars, FWD / Gen 2.5 trucks the same bolt pattern on the Water pump and Oil pump so it's possible to convert the FWD blocks to RWD. These motors are cheap, they can be found with fairly low miles and start at $450. You can also just drop it in and the truck can adjust for the new motor somewhat. I do suggest getting a tune done 98+ trucks.

You will want to start with a  97-99 truck (SR or Winter Package or base 3.5L) these trucks are going to have most of the stock parts, you need to swap over. 

Gen 2 92- 93, Gen 2 (94-96), Mighty Max / Delica / Montero Sport see bottom of FAQ
1G 4cyl, see bottom of FAQ for alternate swap info.


1 6G75 Mivec Motor from an Eclipse (2006*-2012) - Cost 650 - 1400  Note: 2008- 2012 models have different oil housings for the Mivec controls and will have less of an issue with fire wall clearance. The newer setup uses a single solenoid and single housing, the drivers side head is connected with a oil line on the back side of the head to run the Mivec - This is how the Gen 4/5 Mivec Pajero's are setup on the global market

* 2006 - 2007 - You can swap over the shorter oil control housing to the older motors but it will have to keep the second Mivec housing on the drivers side to work.

2. 6G75 Mivec motor from a Pajero - JDM engine places can get them. There is even one on ebay new in a crate for 3k right now in AU. 

3.  6G75 Non Mivec FWD - This is a easy conversion that doesn't require anything super fancy, though a tune would be optimal. Directions are the same as the Mivec motor in tems of the parts you need to make it work. $450 + and will take you up to 245 hp.

3. Hybrid motors / Paj Evo setups * For those looking to do more exotic builds or swaps.

1. 30M swap, this is 266HP 3.0 Dohc Mivec motor, you will need a 94-96 Truck for it's manifold and plenum .

2.You can take 30m heads Dohc Mivec and put them on 3.5 Dohc Block. That will get you the base setup of Paj Evo. If you were looking to do something more exotic you can do the same setup with 3.8 stroker motor, it will require custom pistons and 3.8l crank. This is perfect if you have 94-96 and are really bored and want a harder project.

Parts to swap over - I suggest putting in all new seals/ gaskets / hoses everywhere since you have the motors apart. Don't forget the front pump seal on the trans either.

Block + Accessories

1. Oil Pump ( I suggest getting a new 3.5 / 3.8 Oil Pump) I cross referenced the part number and the Mivec and Non Mivec motors have the same part number.
2. Oil Pan - Will need to tap bock for two bolts and swap over your oil filter housing
3. Oil Pick up * See info in fabrication section
4. Your stock crank sensor
5. Water pump for your 3.5L or 3.8L (Gen 3) (I suggest getting a new Aisin unit), water pipe (small and large) , thermostat housings , cross over water pipe at the rear of the head
6. Flywheel , Flex plate , Starter plate
7. 3.5L / 3.8L Exhaust manifolds (the ones that are on your truck any 3.5 including sports) or Headers Pacemaker / Wildcat / Hurricane / Genie will fit but will need some tweaking the NL-NM models Gen 2.5 (3.5 round port) - Gen 3 3.5/3.8L . Some international models don't have EGR so headers and import exhaust manifolds might not have the ports, check before you purchase.
9. Motor mounts - * Fab required (See fabrication section)
10. Timing components - 3.5L / 3.8L Timing belt, 3.8L Eclipse tensioner, tensioner bearings * you need to take over the spacer from the old motor for one of the bearings.
11. Rest of your parts from your truck (Accessory girdle, Alt, Starter, AC, PS Pump)
12. Timing belt covers * See fabrication section
13. Knock sensor and bracket (For those who might not have one on their junk yard motor)

Upper end + Injectors

1. Lower Plenum - *6G74 Sohc RWD  ** 6g75 Sohc RWD 3.8L 6g75 Sohc RWD Mivec *** 6g75 Mivec FWD ****
* I suggest a gasket match port for this one
** This is a US spec and will fit older style injectors
*** This is an international part (Can be sourced via ebay and other sites) meant for return-less fuel system setups  and uses different fuel rail mounts, though early 2004 3.8 Endevor fuel rails fit and can me modded for a return.
**** Only works with the stock FWD manifold, it can be modded for RWD.
2. Stock Fuel rail if you are swapping in to a gen 2.5  truck
3. FPR - You will need either 94-96 Dohc regulator or an Adjustable unit, upon researching the Dohc SR unit is the same part number as the Pajero Evo (6an adapters from 3000gt / EVO / DSM) to the fuel rail are cheap and easy to get)
4. Injectors - 305cc or higher (High Impedance injectors, peak and hold) You will want new style with more than 4 holes. The reason I say higher is that a stock eclipse motor is capable of making over 300whp or over 330hp at the crank if you take the cats off and that needs about 360cc injectors.    You will need to know what plugs your current ones have, adapters might be needed.
5. Coils 6g74 Sohc and wires
6. Get Iridium plugs for the Eclipse motor.

Intake Manifolds and TB

6g74 Sohc RWD - This is a long flat pan cake manifold, it will likely give decent low end but will kill all out power, but is the easiest to fit. Requires the EGR port removed and relocated (if required for your truck and emissions) due to the rocker covers being so tall)  My 1997 CA model does not have EGR / My 99 Federal does have it.  You will need to take come material off the bottom of the runners to clear the valve cover. You could also get a Pholnic spacer to raise it up a bit, but the egr port will still need to go from it's current location.

6g75 Sohc RWD 3.8 - This is the exact same unit the Mivec motors are coming with in the Pajeros. I am going to say this one will give the best performance between the two stock units. This manifold requires a bit of clean up near the egr port to not hit the rocker cover. I suspect the Paj Mivec has slightly taller plenum or the flashing on the casting trimmed off more. This manifold is setup for Drive by wire setup. I am in the process of working out the brackets for the two cables (Throttle and Trans Kickdown). RPW did this on RHD Gen2.5 so we know it works. This manifold might not clear trucks with out a 2 inch body lift. I also suspect that gen 2/2.5 / 3 (3.5) trucks will need their rubber intake boot changed to custom metal pipe as the tb will not be in the factory location - No easy way to make this work on 2g truck

6g75 Sohc FWD 3.8 - You can mod this to work with some cutting and welding (I saw it being readied ) for Delica Mivec swap.

6g74 Dohc 3.5 RWD - Fits but man it but as one member who got this working on his set said.. It's a jigsaw puzzle. This requires a mix of parts to work. More on this later

Custom manifold - more on this later

You will have to use your stock unit. Gen 2/2.5 can have their 60mm units bored out to 65mm. I am sure the gen 3 3.5 is going to be the same deal. 3.8 drive by wire units, I would leave stock, my experience with Nissan's leads me to believe this would fuck up the unit's calibration.

* for those swapping in to earlier models (you will need gen 2.5 unit) I suspect that 94-96 will also work fine and might be larger, don't have one to measure. (if you have one out of a truck) send me the info and I will add it.

Fabrication Required -

Motor mounts -
1. You will either need to tap the block to some larger bolts or weld some plates to reach the already tapped bosses.
2. Weld on a boss and tap.. *Get an expert welder to help with this, welding on cast iron is not easy)

Oil pick up - You will need to cut the baffle and massage the pick up to fit - Will add photos of this.

Oil pan - You need to drill and tap two bolt holes

Cable bracket - For the 6G75 manifold you will need to fab the Throttle / Kick down bracket and brackets for the coil ignitor.

Manifold Brackets - You will need to make some to keep the manifold from moving and attach them to the head.

Block drop in brackets - You will need to find or make one so you can drop the block in safely for the passenger side.

Timing belt covers - Since this is an unsupported configuration you might not get the same coverage with the factory 3.5 covers, you will need to use the lower 3.5 unit and cut the ones that came on the Mivec motor (Eclipse).

Other items

Fuel Pump - You will need to seal a denso pump out of any 300+ HP car that uses a return style fuel system. 3000GT TT, Supra, 300 ZX, Subie, EVO or an aftermarket unit.

ECU - * All of these will need some or a ton of wiring depending on the truck the motor is going in.Listed in cheapest to most expensive. The closer to stock the ECU is the more sensor compatibility there is. Aftermarket ECU's allow for all sorts of fun stuff like digital clusters, speed density and other control. Gen 1 - 2.5 trucks. Gen 3 trucks will just need their stock ECU reprogrammed as it controls their trans too. 

1. 98/99 Dohc NA 3000 GT ECU - Will need to be tuned * May or May not run the Variable intake manifold, has electric fan and knock control.No Mivec
2. 98/99 Montero ECU Modded * will need to add knock control circuits and tune. No Mivec
3. Chrome ECU - Can run the Variable intake manifold (Mivec control is still being worked out) Mostly Plug and Play to the harness, has electric fan and knock control. Can be used for forced induction and has ODB II and emissions monitors (Fed and CA)
4. AEM EMS Infinity or AEM Series 2 for 3000GT (First gen units were GEMS UK ECUs, same one many WRC teams used back in the day, they have since been spun off as Simtek)
5. Haltec - I have not used one of these in over 15 years so not sure of the current offerings
6. Megasquirt - I have not used one of these as a stand alone yet.

Wiring and connectors - They can be purchased at the link below. Make sure you buy shielded wiring for the knock sensors and the correct factory sealed connectors / wiring type. Sheridan has been selling these items for the DSM/ 3000GT crowd for a long time and are good people.

Mivec Triggering

MSD Window Switch
Bride Vtech / Mivec controller
AEM Infinity has controls for Mivec / Vtech stock

Cooling - I suggest a higher capacity alloy radiator (ADD will be selling a nice US made unit shortly) and electric fans and second trans cooler with electric fan. I also suggest a coolant pressure / level system so if you happen to drop a hose and leak coolant it warns you so you don't kill your nice new motor.

1. Clean and refurbish your factory radiator if you are not going to get high performance unit.
2. Install new fan clutch (they are cheap and it's way easier do it now
3. Flush new block (who knows how long it's been sitting with coolant in it)
4. Convert to electric fans.

Exhaust + Cat - If you are looking to make the full power out of the motor, you will need a 2.75 or 3inch single pipe unit with cat / cats to match. There is a table in the link below to give you an estimated size of pipe required. You may or may not need a body lift to make it happen.  If you make any changes to your emissions system make sure they are legal in your state.

Engine Monitoring - I am going to go with MAD man Engine monitor system. AEM EMS will allow for a digital panel and monitors. You may also want an EGT or AF/ Ratio gauge at the very least

Transmission - The Aisin Warner unit in Gen 2 trucks is good for about 320/330 HP. They can be rebuilt to handle over 900whp.

1.Install fresh fluid and filter
2. Transgo shift kit if you are down there already.

Misc Parts and things to do if you are already in there.

1. Extend Trans / Diff / Center diff breathers while the motor is out and they are accessible.
2. Change front Trans pump seal
3. Back flush heater core
4. Change heater core hoses
5. Add heat protection to wiring looms, especially if you add headers.
6. Add bungs for EGT and a Wideband.
7. Mivec Emblems - No point in doing any of this if you can't put a sticker or emblem on the truck.
8. Use a Eclipse oil filter, it has higher filter flow and different bypass valve PSI - Use a good brand like Wix or Purolator Boss
9. Use 10/30 Synthetic oil or 5/20 if you are in a cold area.

Big Brake upgrade - More power means you need bigger better brakes - Will add info on this with part numbers.

Other Trucks

Gen 1 4 cyl trucks - You need to look at doing 2.4 Turbo or 2.4 Dohc swap - I have that planned for a Starion build and the tech info will be the same for you. You will need a 2.4 wide block 4g64 out of D50 / Mightly Max from the 90s. 1 or 2 G head and wire harness out gen 2 eclipse and ecu (98-99) is flashable. Gen 2 works better because the cam and crank sensors are on the front of the motor vs the back of the head (they make it hard to convert to rwd) when they are there.

Gen 1 V6 - I suggest getting a harness out of junked truck and the ECU / MAF / O2 and all the other parts needed for the conversion (I have found gen 2.5 trucks with blown motors as low as 300 bucks) So if you have the space you can scavenge what you need and sell the rest to cover costs.

Gen 2 94-96 DOHC Trucks - This swap will work just fine in your trucks too, you already have knock sensors and variable induction, but your ECU's are not flashable - You will need a 3 plug chrome ECU or EMS to do this swap. List of required parts

6g74 SOHC - Alternator bracket (one from a 3.5 sport fits)
6g74 SOHC - Intake and plenum or alternate intakes discussed above.
6G74 SOHC - Water pipe (rear, thru heads,) + thermostat housings, water neck.
6G74 SOHC - Exhaust manifolds-
6g74 SOHC - Brake booster line (if not using your stock manifold)
6G74 SOHC - cooling fan, crank pulley, various fan pulleys. Fan clutch. temp sensors.

Montero Sports - 98/99 - I suspect you just need to follow the gen 2.5 instructions for these with 6G74 SOHC


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Re: Gen 2 / 2.5 Mivec Swap
« Reply #1 on: November 12, 2017, 11:28:12 PM »
Awesome info! Thanks for compiling all of this, I know it is taking a lot of time and some trial and error to.crack the code!


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Re: Gen 2 / 2.5 Mivec Swap
« Reply #2 on: November 12, 2017, 11:31:34 PM »
yeah and a good bit of loot too  :o
Awesome info! Thanks for compiling all of this, I know it is taking a lot of time and some trial and error to.crack the code!


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Re: Gen 2 / 2.5 Mivec Swap
« Reply #3 on: November 13, 2017, 07:10:59 AM »
Is this the Chrome ECU you're speaking of?

1998 Montero Winter Package (For Sale)
1994 FZJ80 Land Cruiser (Wife's)
2006 V8 4Runner Sport Edition (Mine)


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Re: Gen 2 / 2.5 Mivec Swap
« Reply #4 on: November 13, 2017, 11:04:32 AM »
Good start. Iíll have to chime in on a number of items when I get a minute.


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Re: Gen 2 / 2.5 Mivec Swap
« Reply #5 on: November 13, 2017, 12:59:26 PM »
Not 100% there yet.. still lots of info needs to be filled in. Just PM / FB me and we can add / correct items.

Good start. Iíll have to chime in on a number of items when I get a minute.


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Re: Gen 2 / 2.5 Mivec Swap
« Reply #6 on: November 14, 2017, 08:04:19 AM »
Holy crap, this is awesome, Leo.

Who reflashes SOHC 6G75 Montero ECUs for such a project?


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Re: Gen 2 / 2.5 Mivec Swap
« Reply #7 on: November 14, 2017, 08:42:40 AM »
Gen 2 or 3? Gen 3 is a different animal
Holy crap, this is awesome, Leo.

Who reflashes SOHC 6G75 Montero ECUs for such a project?


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Re: Gen 2 / 2.5 Mivec Swap
« Reply #8 on: November 15, 2017, 01:01:10 PM »
Gen 3 - 2003 6G75. I'd have to get that ECU flashed, right?


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Re: Gen 2 / 2.5 Mivec Swap
« Reply #9 on: November 15, 2017, 05:28:59 PM »
Merlin.. I have been emailing back and forth with him.. I don't suggest the swap on a DD until the electronics have been worked on each gen. The mechanics are all but worked out.

Gen 3 - 2003 6G75. I'd have to get that ECU flashed, right?


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Re: Gen 2 / 2.5 Mivec Swap
« Reply #10 on: November 15, 2017, 07:13:18 PM »
Great write up!


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Re: Gen 2 / 2.5 Mivec Swap
« Reply #11 on: February 02, 2018, 12:01:55 PM »
looking forward to getting this done in the near future.
Gen 1 1987 Radier 2.6 ( sold )
94 Montero LS with 93k miles
99 Montero overland ready.


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Re: Gen 2 / 2.5 Mivec Swap + 3.8 Swap info
« Reply #12 on: February 03, 2018, 10:57:59 PM »
new info added