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The 6G74 Conversion - what you need to know.

118197 Views 130 Replies 39 Participants Last post by  jose.alonso
Why put a 6G74 in my N/A?
The increased displacement means plenty more downlow torque. The proper engine to use, from a 1992-1998 Mitsubishi Debonair pumps out an impressive 191 kW or 256 hp according to Wiki (I’ll confirm this myself when I hunt down a debonair brochure!) So not only does the bigger engine produce more torque, but it also produces more power. It’s a win-win situation!
Advantages vs Disadvantages

Advantages of a 6G74 DOHC

  • To any Jo-blow it’ll look like a stock 3L
  • More torque
  • More power
  • More return for the same mods done vs a 6G72
  • Plenty of potential to stroke, or turbocharge, with fantastic results.
  • Parts are NOT hard to come by as some may think. Timing belt is simply a Pajero/Montero 3.5L DOHC belt. Not available in Kevlar though.
  • Price is similar if not the same as a 6G72

Disadvantages
  • You MUST ensure the engine you buy is complete. Alternator/power steering brackets, crossover pipe, and water tube from the water pump is a MUST.
  • You will get the bug for more power and more torque from your engine....it’s a very fun drive!
  • Lower stock rev limiter on the debonair (6200RPM) means the powerband isn’t as wide.
  • Taller engine means it might interfere or come close to your front strut brace/tower bar.
  • Your stock downpipe will bolt up with some 1cm spacers from your local exhaust shop. You’ll need 4 gaskets in total and she’ll bolt right up.
6G74 Specifications

6G72 6G74
  • Bore: 91.1 93
  • Stroke: 76 85.8
  • Crank Offset Radius: 38 42.9
  • Rod Length: 140 152
  • Piston Compression Height: 31.75 31.75
  • Deck Height: 210 228
  • Main Bearing Diameter: 60 64
  • Rod Bearing Diameter: 50 55
  • Compression Ratio: 10:1 10:1
  • Piston Pin Diameter: 22 ??
  • ROD Ratio(L/S): 1.84 1.77

  • Engine Size: cc 2972 3497

Correct vs incorrect engine to buy
You are wanting as a direct bolt-in solution an engine from a FWD Mitsubishi Debonair. Ebay ads will list these incorrectly as Montero or Pajero engines. Regardless of what they say, if the engine looks like that out of a 3000GT then that’s the engine for you. However to be sure I would always confirm with the seller it’s 100% a FWD layout engine and is the one for sale in the pictures.
6G72/6G74 head compatibility
I have read many things stating heads are different which we need to clear up!
IF the engine you are using is from a RWD Pajero or Montero, YES the heads are different!
IF the engine you have is the proper JDM Debonair engine, NO The heads are 100% the same!
I have confirmed this with ASA (The Mitsubishi parts program) so there should need to be any more false information floating around the forum anymore.
To put it simply, if you have the FWD model, you are 100% good to go.
Parts interchange-ability with a 6G72
I have been working on my 6G74 for a few years now and I now have a good idea of what fits and what does not.
Here is a list of parts I know of that WILL fit onto your 6G74 weather right away, or if you need spares
Intake (from air cleaner up to TB)
Throttle body
Upper intake manifold (it is actually 3mm longer than a 3L one so technically different but for argument's sake, it’ll work with no problems)
  • Front rocker cover
  • Front timing cover
  • Coil pack and PTU
  • Exhaust manifolds
  • Alternator
  • Power steering pump
If your 6G72 is a 93+ with dual serpentine belts, the Crank pulley will work
Parts which are different
  • Lower intake manifold on the 6G74 is wider for the wider V of the block
  • Rear rocker cover and rear timing belt cover are different. One solution is to use your 3L ones. They are different in that the bolt hole spacing is closer on the rear rocker cover/timing belt cover than they are the 72 ones. I cannot confirm if 1993+ 6G72 rear rocker cover’s and timing belt covers are different/the same as the 1991-1993 models.
  • Alternator/Power steering bracket
  • Sump is 2 piece. 6G72 is one piece.
  • Lower timing cover is taller aswell.
  • Injectors will fit however DO NOT use 6G72 Injectors.

Modifications to enhance your N/A 6G74
Adding adjustable cam gears and setting them around the normal -3 +1 adjustments will give you a lot more mid and top-end power. I noticed the power would drop off sharply around 6300RPM before adding them, with them installed it would rev nice and smooth all the way to 7000RPM

A/C Delete. I did this as I cannot really be bothered using my A/C. Deleting it saves close to 20kg in total. I kept the upper pulley. I used a 6PK1035 belt. Fitted perfectly.

272 camshafts. I have recently installed a set of DR 272 reground camshafts w/shims. I haven’t had a good chance to take the car out for a test’n’tune so I cannot comment on these. Let’s just say that you won’t be making LESS power with them that’s for sure!

Common Q’s and A’s
Will it bolt right into my 3000GT/Stealth?
If you own a FWD Model, YES, this engine will 100% bolt right up
Will my fuel system need upgrading?
If you are upgrading from a SOHC 12v 6G72 then YES, your fuel pump will need upgrading.
If you are upgrading from a DOHC 24v 6G72 then NO, it will not need upgrading.
Will it work in a 1993+ car?
Yes, All electronics will plug right up if your car/engine harness has the two separate plugs for the separate crank and cam angle sensors on the timing belt side of the engine
If you have a 1991-early 1993 engine you will need to perform a wiring modification to adapt to the new harness
Will my 3L ECU run right away?
Yes, your 3L ECU will fire it up right away.
Due to the aggressive timing of the 3L it is recommended to only run High octane fuel to prevent any chance of knock. There have been cases of a few 6G74 engines running 6G72 ECU’s failing because of this.
Will my Transmission bolt up?
Yep, no worry’s here. Your manual gearbox will bolt right up, as will your automatic transmission. The bolt pattern is exactly the same.
I have some spare injectors from my 6G72, can I use these?
Technically, they will bolt up and work. However they are a smaller capacity so refrain from using them at all costs. Playing around with fuel injectors without proper fuel control can turn nasty. It’s best to avoid these hassles in the first place.
I have a spare 6G72 Oil pump, can I use it?
Only if it's from a 1993+ onwards car. In fact most of the lower timing belt components will work aswell, timing tensioner, idler pulley, hydraulic tensioner, that swing arm that is being pushed on by the hydraulic tensioner. Even the lower CAS plate and sensor will work.

References;
6G74 3.5L Engine Main Swap details!...JOHN MONNIN'S PERSONAL 3000GT/STEALTH FAQ
Mitsubishi Debonair - Wikipedia, the free encyclopedia

I made this to be a quick stop for people considering this conversion as there is an influx of basic questions always asked. If ANYONE has something to contribute, please PM me and I will modify it and/or add/remove things.
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Question for you guys - the 6G72 oil filter stay (MD140084) doesn't appear to line up to the 6G74 block. Am I correct in assuming that nobody runs that stay on their 6G74 swaps? Thanks

Edit: John M. already answered this on his page (http://www.wrenchjockey.com/Webpages/6G74swap.html), it doesn't line right up, but the question remains. Anyone just not run it?
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True...I've heard 3000GT engines are similar to Pajero engines in USA.
Question for you guys - the 6G72 oil filter stay (MD140084) doesn't appear to line up to the 6G74 block. Am I correct in assuming that nobody runs that stay on their 6G74 swaps? Thanks

Edit: John M. already answered this on his page (6G74 3.5L Engine Main Swap details!...JOHN MONNIN'S PERSONAL 3000GT/STEALTH FAQ), it doesn't line right up, but the question remains. Anyone just not run it?
I honestly can't remember using mine... I don't think I ever had that bracket to begin with... never bought a completed car, so mine was kind of pieced together.
Never had this bracket on mine either. Running the TT oil filter housing anyway.
Hello from Europe,

I'm currently looking into getting a new engine / overhaul for my GTO TT.

There are alot (compared to the 3S / GTO) Pajero Engines for low prices here. 60k miles Pajero Engine is around 1400$, a 150k miles F*** up GTO Engine is 2900-3500. (Which probably needs more work than my 150k one).

So the option to take a pajero is pure economic.Not chasing huge Power but around 400 tops. (Drop in engine, and finetune with Chrome +ECU).


Alot of those are 3.5 GDI and some 3.5 DOHC non GDI Pajero Engines.

I did read through nearly all threads, and, 6G74 3.5L to 6G72 3.0L comparison Pictures!...JOHN MONNIN'S PERSONAL 3000GT/STEALTH FAQ this one.

But still there is alot confusing information out there when not having the option to go for a debonair 6g74 one.


For a Pajero the Waterpiping is on the wrong side.
Welding water & Thermostat housing to the correct side isn't an issue.
Fitting / cutting / Welding the 6G74 oilpan and dipstick (With turbo inlets) isn't either for me.
Don't need the PS and Aircon so brackets are not a worry for me.
Oil Filter mount is used from the 6G72 TT block.


But what's confusing is,


Is the Harmonic Balancer pulley used from the 6G72 always even on the Pajero? Just curious if I should go with the Pajero Alternator or not.

The 6g72TT 3T Heads with valves and cams bolt on the 6g74 shortbock?
If I understood correctly the 3A Heads from a non GDI fit, but a GDI one is completly different?
The 6g72TT Exhaust Manifolds bolt into the 3A Heads if you fit them? Or is fittment required?
Cam Gears are used from the 6G74 or 6G72?
Waterpump is from the 6G74?
So timing Belt is 6G74.^
Oilpump is the same as the 6G72 93+?



Concerning 6g74 GDI - different pistons and heads and lower intake? So I would need to Source 6G74 Cam Gears and pistons (e.g. 8: Turbo compression ones from 3sx?) and lower intake.

If I get a DOHC 24V 6g74 non GDI, I can reuse lower intake and 3T heads and running 10: something compression with lower boost?


Thanks for the clarification.
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Beating this dead horse.

Just have some questions.

How different are the pajero/montero 6g74 heads. TT heads are good to just swap right on? Right?

How do you know what to look for so the motor your looking at has all forged internals? Is there model number or something?

Do they have same correct oil passages required to turbo them and just throw my 6g72 TT billet 15gs right on them? Without issues.

I Know the basics that it has to be transverse mounted and it looks exactly like 6g72 in the photos. (If its not this, its wrong right?)

Lastly, there is no trickery here right? if you get Montero engine. Like how do you tell correct montero/debonair/pajero apart. I don't want to get wrong engine without correct internals.
1994 1995 1996 (listed as)

For AWD 93+ TT car.

Thanks
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Duplicate. Deleted message.
Question for you guys - the 6G72 oil filter stay (MD140084) doesn't appear to line up to the 6G74 block. Am I correct in assuming that nobody runs that stay on their 6G74 swaps? Thanks

Edit: John M. already answered this on his page (6G74 3.5L Engine Main Swap details!...JOHN MONNIN'S PERSONAL 3000GT/STEALTH FAQ), it doesn't line right up, but the question remains. Anyone just not run it?
I’ve never run that bracket and had exactly zero oil filter housings fall off the engine.
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Beating this dead horse.

Just have some questions.

How different are the pajero/montero 6g74 heads. TT heads are good to just swap right on? Right?
DOHC 6G74 heads are the same part number as 2G N/A 3S heads. So yes, turbo heads are a bolt on.

How do you know what to look for so the motor your looking at has all forged internals? Is there model number or something?
Unless it's been rebuilt previously with an aftermarket Chinese replacement crank, They are all forged.

Do they have same correct oil passages required to turbo them and just throw my 6g72 TT billet 15gs right on them? Without issues.
You'll need to swap on the Turbo oil pump and oil filter adapter.

I Know the basics that it has to be transverse mounted and it looks exactly like 6g72 in the photos. (If its not this, its wrong right?)

Lastly, there is no trickery here right? if you get Montero engine. Like how do you tell correct montero/debonair/pajero apart. I don't want to get wrong engine without correct internals.
1994 1995 1996 (listed as)

For AWD 93+ TT car.

Thanks
The Montero/Pajero motor is a longitude mount truck motor... The long block is the only part you'd be able to use. All accessories, oil pan, etc. are wrong. The Debonair or Hyundai Grandeur had the FWD version that is almost a bolt in swap. They are Asian market vehicles that never made it to the states, and you'll need to find one from a JDM engine importer.
the Kia 3.5L DOHC from early 2000's is identical, but FWD - you can use various parts off of it such as Lower Intake Manifold, *SOME* timing components, water pump, etc. Crank is forged, 4 Bolt mains, etc etc

when I built my 6G75 with 3/S DOHC Heads, that is where I got the missing parts to make it work - they are EXTREMELY Cheap and very plentiful on ebay, and rockauto.
the Kia 3.5L DOHC from early 2000's is identical, but FWD - you can use various parts off of it such as Lower Intake Manifold, *SOME* timing components, water pump, etc. Crank is forged, 4 Bolt mains, etc etc

when I built my 6G75 with 3/S DOHC Heads, that is where I got the missing parts to make it work - they are EXTREMELY Cheap and very plentiful on ebay, and rockauto.


Does the 3.5 Kia swap in? The debonair long blocks are getting harder to find.
Ok Thanks a ton. Just waiting on Dave & Ray to get back to me.
Does the 3.5 Kia swap in? The debonair long blocks are getting harder to find.
It's the closest thing to being usable I've seen in the US market, but still far from a direct swap. As in most 2000-up Mitsu products, it faces the passenger side, making the mounts and accessories different. (2002-2005 Kia Sedona minivan)
It's the closest thing to being usable I've seen in the US market, but still far from a direct swap. As in most 2000-up Mitsu products, it faces the passenger side, making the mounts and accessories different. (2002-2005 Kia Sedona minivan)

https://www.ebay.com/itm/Engine-3-5...ke:Kia&hash=item2624c7c643:g:fiMAAOSwVcFdWxeV
What about the 95-96 montero?
I’ll probably just stick to a 4Gswap in my son’s car. Don’t want too much hassle with the swap. 3.5 auto and a little boost would be fun little car. He wants to do Race Week so 4Gswap is probably better still for what he wants to do with it.

Carry on.
What about the 95-96 montero?
94-96 Montero SR.

Right lower end and heads, nothing else is even close.
Does the 3.5 Kia swap in? The debonair long blocks are getting harder to find.
Kia/Hyundai heads look identical, oil pumps are different ( i believe theres a thread on using xg350 oil pumps on here)

Valve covers are different, surge tank is different (i think the lower is the same and can be flipped around on the fwd ones), oil pan upper and lower are different (was checking oil pan on a few since my 74 came with a crushed lower)

Water pumps/housings and intake manifold on the rwd sorento is definitely different, but id assume a fwd 74 one would bolt up, the kia/Hyundai ones would put heater hoses and such facing the wrong way though.

Ive only had one out of the car but didnt get a chance to see if engine mount or accessory mount bosses would be the same. They were very good engines that only had cam sensor or coil pack issues most of the time (besides the sorento balancer bolt backing out which sometimes snapped in the crank making you get a new crank)

Edit: found this

Making a hyundai 6g74 block fit..
94-96 Montero SR.

Right lower end and heads, nothing else is even close.
I know this is foreign in 3s land, but how hard is it to make a few brackets?
The Kia 3.5L DOHC and 3.8L 6G75 with 3/S DOHC heads seem to have the same challenges for mounting - overall not that bad

Odd ball oil pump with OFH what becomes Rear of engine to us, causing it to be in way of intermediate shaft - no 3/S oil pump will work from what I could tell.

I just made a block off plate out of 3/8" thick aluminum, and used the two oil ports on the back with the threaded plugs in them to feed my Remote Oil Filter housing via -10AN fittings and Lines. I believe they are BSP/BTSP/BSPTSPSTPS thread but I don't remember exactly what size.

Oil Pan required mild modification to work with 3/S Trans.
*Drain and Dip stick on rear of engine. Dipstick provision is in oilpan itself not block
*No Starter notch, I took some aluminum tubing, cut a section out, sliced the tubing and welded it into the pan - I also had to grind some material away from the girdle - a AWD TT Trans might not need this since the starter sits out further from the engine slightly with the bigger diameter flywheel
*Hack off the brace type thing on the transmission side and use shorter bolts for the pan.
*Much like the JDM 6G74, you'll need to notch the oil pan for the T-Case which means grinding the crap out of the Girdle there too.

a 4 Bolt TT Pan will NOT work, I tried.

I was able to get by using all 72 brackets, and accessories with light to mild modification. Power steering, Alternator, Drivers Motor Mount Bracket boat anchor, etc.

Most of which consisted of Grind away material and or enlarging holes... not the right way but it worked. 3D Scanning the block and heads then having all the parts cut out of aluminum via CNC would be the preferred way to do it given the resources.

the Bosses for the Front and Rear Motor mounts were there, but most were not drilled/threaded the right size or at all.... However making some custom front and rear motor mounts was actually pretty easy coming from someone who is a terrible fabricator... later on in the project I ended up using the IMR Motorplate, which made mounting the engine fairly easy...


The rest is basically the same as the JDM 6G74 Swap guide,
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