[TUFFTR]

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.

 

[TUFFTR]

here is a not so commonly answered question (or two):

where is the best place to source some of the parts needed? for instance, if you have a montero block but need the a/c bracket or p/s bracket?

also, will the oil pump from a 6g72 bolt right up? (not sure if the added deck height would matter or not). and if you have the part number on hand, the correct timing belt to use would benefit others as well

The oil pump from a 6G72 2ND GEN ONLY will work! So thank you for that question, I'll add it in. In fact, alot of the timing belt components such as the idler bearing, tensioner bearing, the swing arm and the hyrdraulic tensioner are all 6G72 items. It's pretty much anything that's around the head area (water pump etc) which won't fit from a 72.

In regards to brackets, that's something I really do not know. My advice would to to visit as many local jap wreckers as you can. I visited one 15 minutes away and they had a heap of random debonair parts just laying about, so that was pretty lucky.

 

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I'll just add, for correct part numbers, Please visit John Monnins link down the bottom. He has all the correct part numbers listed and a more in-depth look. This sticky is just to hopefully save a few basic questions from being answered!

 

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well. great info....just question...
will 1997r shogun *pajero , 4wd , 3.5 v6 DOHC...
i know it is not bolt on....just need to know more less what will be needed to change beside oil pan and , thermostat housing and few more things mentioned in thread.
i am going to put it to 93 3000gt TT .

if it is not croosover what does it really mean?

Hi mate....Cheers!
The Pajero one will fit in. The engines that are still classed as a 6G74 but won't work are mainly the ones found in the 96+ Diamante's The oil pump is totally different shooting the oil filter out on a the wrong side hitting the driveshaft.

It's explained in detail on John Monnins website.

You''ll need to use complete 3000GT heads as the Pajero ones are different.
What else what else....intake manifold which is a given....I'm not 100% on the location of the accessory's such as the P/S pump, Alternator and whatknot as I haven't had entirely alot to do with the Pajero engine.

 

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Looking for a 6G74 engine. After reading this thread, apparently I'm looking for a Debonair but I've also seen some Diamante 6g74 engines. Any reason to avoid a Diamante 6G74 or is any FWD 6G74 OK? Any recommendations for a source. I called Eric Japan Engines in Chicago and he didn't have and could not get one.

Good question.
You are looking for a 3.5L Debonair engine.
There is NO such thing as a 3.5L Diamante engine (In this configuration anyway)
It's a common mistake made by wreckers as both engine's look identical. The Diamante of that year in JDM form only came in a 2.5L DOHC and 3L DOHC (Also a 2L SOHC FYI) But NEVER a 3.5L.

So, If it's labelled a Diamante 6G74 but looks identical to a debonair one (actually should look identical to a 3000GT one basically!) Then it's your engine!

Montero/Pajero DOHC's are RWD, so they'll look totally different in layout.

If you find one, post it up or PM me and I'll double check, But it should look exactly like a 3S motor. I'm 99% sure there was never another FWD layout engine of this sort in 3.5L BUT the debonair.

 

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so ive read many of threads on the 6g74 motor and have not been able to find if there is a specific year or specific model of the debonair or jdm 3.5l that has a "Forged Crankshaft" and rods!? im looking to buy a 3.5l debonair motor for a swap soon and am looking to find which ones have the forged crankshaft ive read about

The debonair with the 3.5L was available from 93 onwards.
AFAIK, and again, I need to confirm this (possibly through ASA) But ALL 3.5L's have the forged crank and rods.

If someone can confirm that that'd be great, but to the best of my knowledge there are no cast 3.5L DOHC cranks.

 

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im doin a 3.5 94 montero swap and i knew the water housing would be all different can i bolt on a water housing from a different year 3.5 that is set up more like a 3/s water housing?

Great question. I'm not 100% on if any Hyundai 3.5L's can be used, or if even a SOHC 24v Diamante water crossover can be used.

Would be interesting to know though for future reference. Is it possible to head to a wreckers and rip one off a 3.5L Diamante?

 

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i need new engine mounts on my 6g74... uhm should recommend that since the power is greatly increased, the pressure on the mounts have too, dramatically. and had a slight problem with rear mount, but if you flip it around, it fit in. but still question, where can i get new engine mounts that will fit my stealth for a 3.5

3L Engine mounts will be just fine. I used all my 3L SOHC engine mounts when converting. So your regular 3SX poly's or any aftermarkets will do the job.

Agree on the torque side of things though. I installed a brand new front mount (rubber) which has gone to shit in under 15K. It's really copped a beating.

 

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When going from a sohc stealt to a dohc 3.5 how do i modify the harness for the alternator?

Well, I did this exact swap, except I made my own engine loom as Im running an aftermarket ECU.

However for the alternator it's pretty simple.

Bare with me here it's been 3 years since I did this.
Alternator has 3 wires. Pretty easy. I used some 4ga stereo wire with professionally soldered on ring terminals to the fusebox (should be a 100A fuse I think?!)

Then you have two small wires going to the plug, this is where my memory fails me, however even a basic wiring diagram will show you easily, One is a 12v positive wire to the alt, and I think one goes to the dash light as a warning.

That's it. It's pretty easy to make your own loom and just incorporate it into the existing wiring of the car.

Again, grab a DOHC engine wiring diagram and this will show you what needs to be done.

 

[TUFFTR]

we couldnt get the rear mount to line up for the bolt. thats why we turned it around and but still had t torque it to align. or is it just me...

Strange dude. I'm using 6G72 SOHC engine mounts still! All lined up perfectly.

 

[TUFFTR]

hi there so much info head hurts so can a 6g74 non turbo fit in to a 6g72 non turbo in a 1990 awd gto i am a bit simple but i want the horse power sounds great my 6g72 is dohc if that makes a different are the wiring harnesses the same and what cross over pipe would i use Water are the ecu's the same?. thanks mate

Wiring harness's the same - Since yours is a 1990 you'll have the one CAS unit on the rear head near the air intake. This will mean you have 2 options. Do the wiring modification to use the Seperate cam/crank angle sensor that comes on the 6G74, or swap the heads over.

Cross over pipe, You need the 6G74 one. ECU's are not the same. This is a bit of a grey area for me here which Ive quickly touched on. From what I know you will need to use the highest octane petrol you can all the time.

If you havent mate, read over John monnin's page. This is the holy grail of 6G74 conversion websites which I used for info when doing mine. EVERYTHING is listed here. If there is anything I can do, please let me know

 

[TUFFTR]

I got the water housing figured out now i got one good question.

What head gaskets do i use if your putting turbos on?

which ones did you use and what thinkness

I know these use the Graphite Gaskets. Might be worth seeing if the Montero/Pajero's which have the DOHC use MLS gaskets. From what I read on here ( -read- I don't own a TT car!) everyone seems to dig the OEM MLS gaskets for ultimate reliability. Any pictures of your water housing solved would be great

 

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so how about cosmetics.. what spark plugs do you guys use on your 3.5 and what oil, how many qts. im just curious. i've always put in around 4 but just curious if there is a specific amount.

Recommended plug is a platinum BKR5EIX-11. I use normal coppers so I use BKR5ES-11
What oil, 15w-60 in summer and a 10w-40 in winter.
Oil, about 4.5L with filter.

 

[TUFFTR]

hi mate are the magna 3.5l a 6g74 and its all the same yeah?? im thinking off buyina a magna 3.5 complete car then i will have every thing i need i think any additions

Hi mate no......
There are so many difference's I don't know where to start...first of all they face the wrong way and are SOHC to name a few easy ones.

You need a DOHC 24v 6G74 out of a Pajero or PREFERABLY A debonair. If it's a debonair FWD motor it will bolt in.

 

[TUFFTR]

would solid motor mounts work on the 6g74?
my brother just got some for his 3.0 and they look awesome but i was worried they wouldnt even fit to our engines.. i have the dohc

They certainly will mate! I am using all 3L SOHC 12v engine mounts on mine, all work like a charm!

 

[TUFFTR]

Hi mate

I have a bit of a silly question. What differs between the Montero/Pajaro 6g74, and the Debonair 6g74.. both came in FWD, the debonair makes 260 PS (191 kW; 256 hp)
but the pajaro makes 153 kW (208 PS; 205 hp)

and how can I identify an actual Debonair engine vs the Montero/pajaro

OK, They did not both come in FWD. Pajero/Montero was a RWD based engine. So based on that it's very easy to identify the different motors.

The pajero makes less power as being a 4WD it needs it's torque more. High power in a 4WD is useless.

Debonair engine looks EXACTLY like your normal 3L FWD 3000GT engine, simply put, with 3500 on the intake manifold, not 3000.

The pajero one looks 100 times different. Very easy to tell.

 

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of course not. you can put it in a TT with a slight modification to the oil pan to make it clear the t/case

 

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Yep. Well worth it. I don't think you'll find ANYONE who regrets it.

 

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Incorrect. the heads are 100% the same. I have double checked almost all part numbers. They are all identical according to ASA. This is for identical year engines though so this doesn't apply to anything from 91-late 94

 

[TUFFTR]

The ACC belt is longer.
Power steering tensioner PULLEY is the same, the bracket it bolts to is different however