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Discussion Starter · #41 · (Edited)
thank you

I do have none MIVEC 6g75 heads in my garage, although I don't have the rest of the engine, I do plan on doing a comparision to the MIVEC and 6g74 heads later on
 

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Discussion Starter · #43 ·
yep, I also have a few empty girdles and a few rods laying around if you get my drift

I have pictures up of those anyway


anywho, the valve angle (from the centerline of the cylinder head, mind you our heads are a 4 valve pent house roof design) for both the 6g72/6g74 SOHC 24 valve and for the 6g75, are



the same, from the valve face surface to the deck surface for both types of heads, the angle is 25 degrees for both the intake and exhaust, the angle from the valve stem to the deck surface is 65 degrees, in other words, from the valve stem to the cylinder head's centerline (veiwing from the top of the cylinder head) is 25 degrees

also fun fact with my 6g74 heads, I was able to safely port (by hand, with a dremel) the exhaust side up to 45 mm, which is gasket matching the exhaust side, although I frankly have no idea how much meet is in those ports so I would leave any porting for the pros, ultra sonicing (ultra sounding) the ports would be vital for this to prevent hitting a coolant passage
 

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Discussion Starter · #44 ·
my 6g74 block is currently at the machine shop to be checked out and cleaned up (magna fluxed, hot tanked, pressure tested, mating surfaces cleaned), also I am planning on using the MIVEC girdle rather than the 6g74 girdle, so I also handed both girdle to my machine shop (so they can determine if I can use the MIVEC girdle), also I'm using ARP main studs with this combo, so provided the bearing journals are straight enough that some light line honing is required, my 6g74/6g75 MIVEC hybrid is coming together nicely

with that said (and I will get pictures when I get everything back), you can use a 6g75 MIVEC girdle with a 6g74 block, it physically bolts on (but my camera was dead when I tried this out)

anyway, I took some time when I was cleaning my garage and weighed the cylinder heads, without the valve covers
6g74 cylinder head (front head), assembled, unported, weighs 40 pounds
6g75 MIVEC cylinder head (front and rear heads, weighed individually), assembled, unported, weighs 42 pounds
interesting, even with the bigger valves, the MIVEC mechanisms (each head has one), the more complex rocker assemblies and the thicker decks of these cylinder head (pictures will be up soon), this only adds 2 pounds per cylinder head
 

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Discussion Starter · #45 · (Edited)
it's SO clean!



pressure washed, magnafluxed, degreased, the works with no machining actually done, also no hot tanked yet, that is to be done later, block checked out perfectly, my machinist thought the engine was freshly rebuilt due to how good in shape the bores are, my 6g74 had around 70,000 miles before I tore it down (I have the exact mileage on the receipt from my salvage yard, although I don't know where that went off to)





also I trial fitted my MIVEC's main girdle, I put down the main bolts finger tight, with the finger nail test on the bearing bores, I had no snags, it should be usable with the hybrid build (I will be waiting on the word of a machine shop first though)


6g74 oil pan with the MIVEC girdle, clears perfectly (although I can't say how much, I didn't clay for exact clearances)


looking down with the MIVEC oil on the 6g74 block, the bolt pattern for this oil pan on the front of the engine is identicle


however the rear of the engine, the bolt pattern is slightly different, most notably here, the primary reason why there is this gap between the pan and the pan rail is these oil pans are initially located with two dowel pins (on opposite sides of the engine), sometimes they stay with the block, sometimes they stay with the oil pan, sometimes one stays with the one and the other stays with the other, here, the pin on the MIVEC oil pan stayed on the rear side of the engine, same pin stayed with the 6g74 block, I will provide pictures later, but you probably get the idea

I still plan on using this pan, some welding will have to be done to extend out part of the lip of the oil pan so I can have a boss for a bolt hole, but it will be worth it, it is also worth noting the 6g74 pan is visibly wider than the MIVEC pan, I will get pictures and measurements tomorrow

speaking of more differences between the oil pans, here's some more



MIVEC



6g74

there are significant differences between these pans internally, the MIVEC has baffles that are spot welded as part of a bolt in tray that is raised on struts within the pan, there is also a large gap all around this bolt in tray that should provide greater drainage


ok, I will get a picture of this tomorrow
the 6g74 has a simple stamped plate with a few additional holes to provide drainage


as more accurately seen here, this is yet another case of the newer version (well, obviously) being so much more advanced than the older one, similarly with the rest of the parts, this also is that newer version having near race grade (on qsuedo race equivilant) parts that are lightyears more advanced than 6g74


I really love the parts from my MIVEC, dammit this thing is so much like a race engine


much like the intake manifold sections, these trays aren't cross compatible between oil pans, as seen here with the 6g74 tray in the MIVEC oil pan


and vice versa, the MIVEC tray actually protrudes out of the upper pan past where the lower pan normall is
 

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I've built a couple 6G75's with forged internals etc for my supercharged and twin turbo Galants.
Had two failures in these 6G75's by way of main bearings spinning.

My machine shop identified the failures as bolts stretching.
It was proven with a thread gauge, hard to detect otherwise.

It is always the four inner bolts on the two center main bearings.

Solution was to retap the four center bolt threads (don't do the outside ones, not enough block material to work with).

And fit the next size up ARP bolts with larger diameter.

Definitely fixes it....am running 270kw at the wheels and 710Nm torque in the GT.
 

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Discussion Starter · #47 ·
I have ARP main studs made specifically for the 4 bolt 6g72 and 6g74 blocks (weird, I know, one has larger main bearings and a tall deck, the other doesn't) as I will be using a 6g74 block for my build

but noted
 

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Why is this thread not stickied??

Seriously, reading this has made me love my 6G75 even more. The engineering put into this thing makes me think this was designed as a racing engine, or they just wanted to build a good quality engine that would last a long time. Beefy where it needs to be beefy. Precisely delicate on the upper end, but not too delicate that things might go bad when the engine is pushed to it's limits.

Thank you for this great read/view!! :bigthumb:
 

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Discussion Starter · #49 ·
thank you, my thoughts exactly

to my knowledge, Mitsubishi has only used 6g75's (well, kind of, I'll explain) in off road racing, I think at Dekar. They were stroked to 4 liters, use near unobtainium (to import) MIVEC DOHC heads (only avalible with 6g72's and 6g74's, which those with these heads are extremely rare), use dry sump oiling, among many other modifications. I'm almost willing to say, these aren't 6g75's, not that them lacking the SOHC MIVEC heads make that difference, but using SOHC 6g7 heads on a block designed for the DOHC heads requires modifications (because of oiling and coolant passages) and probably vice versa (nobody has tried yet), therefore, it is likely it uses the DOHC 6g74 block. I'm actually thinking they are heavily modified DOHC MIVEC 6g74's that have offset ground 6g75 cranks and specially made pistons.

anyway, I agree, the 6g75 MIVEC (specifically) does at least look like it was developed from a racing engine program, strange thing is, what I described above was used after the 6g75 started to be put in production cars. They sure as hell have a ton of potential, I would be joyous to see them used in pro racing, regardless of the series, the connecting rods and pistons just speak to it was made for high RPM use. For somebody like me who constantly looks for improvements in everything (from basic wiring, to nerf guns to, well, cars, this is part of my personality), if I was in charge of the development of this engine, the changes I would make I can count on one hand, stronger main bolts and rod bolts, stronger bearings (or use 6g74 bears, which is common practice in building these engines), balance the rotating assembly from the factory and make the oil pump gears stronger. In all, I just want to see at least a closing act from Mitsubishi with this engine family if they plan on discontinuing this terrific engine family



anywho, once I get some better bandwidth, I have one, interesting, addition to this comparison
 

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I've built a couple 6G75's with forged internals etc for my supercharged and twin turbo Galants.
Had two failures in these 6G75's by way of main bearings spinning.

My machine shop identified the failures as bolts stretching.
It was proven with a thread gauge, hard to detect otherwise.

It is always the four inner bolts on the two center main bearings.

Solution was to retap the four center bolt threads (don't do the outside ones, not enough block material to work with).

And fit the next size up ARP bolts with larger diameter.

Definitely fixes it....am running 270kw at the wheels and 710Nm torque in the GT.
So what's the best course of action depending on what setup being use, boost or NA: ARP main studs (std or oversize), upgrade to G74 bearings, or a combination of the two?
 

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Discussion Starter · #51 ·
well, interesting update, I got my hands on one of the 6g75 none MIVEC polymer upper intake manifolds with the associated lower manifold (well, quite a few months ago, I got everything shot already), like the MIVEC lower, it requires the same fuel rail design (also same fuel injector angle), and, it has a unique port spacing, unique bolt pattern, and for the throttle body and to the lower manifold (from the upper manifold), it uses molded O-ring style gaskets, I will have pictures up for this soon, I plan on doing dyno comparisons between the MIVEC manifold set and the polymer manifold set (the lower intake manifold is normal cast aluminum, lower might have some welding and porting to better match the ports for the MIVEC heads, I will look into this when I get there) with and without tuning
 

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Discussion Starter · #53 · (Edited)
much belated update!

the polymer upper intake manifold from a 6g75 none-MIVEC engine, special thanks to Bennett6G75

this is a weird one, and extremely cool one, no other way to put it




the MIVEC upper and the polymer upper at first glance are very close to being the same size, but that isn't everything, the polymer intake it as exotic, if not more than the MIVEC upper


this is one of the first unique features, the throttle body port uses an O-ring instead of a gasket, and it integrate a mesh screen on the leeward opening side of the throttle body (read: the throttle body rotates away from the mesh side), I am guessing this is to improve the throttle body response or improve vacuum at small throttle opening, or purposefully causes turbulence on this side to improve fuel atomization on the leeward side, it is something I have never seen before


the polymer upper also appears to have a minor venturi profile as well


the most exotic feature of this intake manifold, the center ports are the most widely spaced, the next more outboard ports (so, numbers 2 and 5, to 3 and four) are narrower spaced, and then the most outboard ports (number 1 and 6, to 2 and 5) have the narrowest spacing, and, this is using an O-ring type gasket, also uniquely, these posts aren't exactly equally shaped, the outermost bore ports are slightly narrower and taller than the inboard ports, and step down the wider ports towards the center 2 (this is in steps of about 0.5 mm, this is equal reductions of height to increases in widths retaining the same cross section), this might be a casting error, or an error from my calipers



as it is polymer, no screw bosses can be made with the existing material, thus, metal must either be cast in, or put in post casting, as with EGR parts, the initial inlet port must be metal to take the heat (so it does not melt), I am certain, as the intake manifolds are, well, bolted to an engine, the plastic used, is thermoset, rather than thermoplastic (meaning, after the casting is cooled, it does not melt at the temperature of that polymer was molten at initially)


just trying out with a MIVEC upper with a stud from one of my 6g74 heads to see if it threads in, it also threads into the polymer upper


and, my stock 6g72 SOHC 24 valve throttle body bolts to it, so, I could use a 6g74 SOHC throttle body, and with the accommodations from the second picture of the cast in metal parts, I can bolt on a throttle body cable with no welding or brazing (unlike the MIVEC upper which I have to)

anyway, onto the lower intake manifold

this gives the greatest view of the difference in port spacing


if you check back to the image of the bottom of the 6g74 lower, this is very, very similar, similar PCV type rail configuration, similar somewhat direct to port PCV venting, bit less external casting flash than with the 6g74 lower


the MIVEC fuel rails do also bolt on and fit on perfectly with either the fuel injectors from the MIVEC or 6g74, meaning it has the same injector angle and location of the fuel rails, this is reminds me of a hybrid of the designs of the 6g74 and the MIVEC lowers


and the 6g74 lower to head intake manifold gasket perfectly matches the ports from the lower intake manifold

I should make note, this lower and upper intake manifolds are for a none MIVEC 6g75, it is pretty easy to say, at least from these parts, the none MIVEC 6g75 intake ports , the the throat (of the heads) are pretty close, if not the very same as the 6g74 heads

it is also worth mentioning, the polymer upper intake manifold weighs (just by hand), about the same as the MIVEC upper (kind of grape fruits to oranges as the engines they are off of are similar, but not the same, but still worth mentioning)
 

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much belated update!

the polymer upper intake manifold from a 6g75 none-MIVEC engine, special thanks to Bennett6G75

this is a weird one, and extremely cool one, no other way to put it




the MIVEC upper and the polymer upper at first glance are very close to being the same size, but that isn't everything, the polymer intake it as exotic, if not more than the MIVEC upper


this is one of the first unique features, the throttle body port uses an O-ring instead of a gasket, and it integrate a mesh screen on the leeward opening side of the throttle body (read: the throttle body rotates away from the mesh side), I am guessing this is to improve the throttle body response, or purposefully causes turbulence on this side to improve fuel atomization on the leeward side, it is something I have never seen before


the polymer upper also appears to have a minor venturi profile as well


the most exotic feature of this intake manifold, the center ports are the most widely spaced, the next more outboard ports (so, numbers 2 and 5, to 3 and four) are narrower spaced, and then the most outboard ports (number 1 and 6, to 2 and 5) have the narrowest spacing, and, this is using an O-ring type gasket, also uniquely, these posts aren't exactly equally shaped, the outermost bore ports are slightly narrower and taller than the inboard ports, and step down the wider ports towards the center 2 (this is in steps of about 0.5 mm, this is equal reductions of height to increases in widths retaining the same cross section), this might be a casting error, or an error from my calipers



as it is polymer, no screw bosses can be made with the existing material, thus, metal must either be cast in, or put in post casting, as with EGR parts, the initial inlet port must be metal to take the heat (so it does not melt), I am certain, as the intake manifolds are, well, bolted to an engine, the plastic used, is thermoset, rather than thermoplastic (meaning, after the casting is cooled, it does not melt at the temperature of that polymer was molten at initially)


just trying out with a MIVEC upper with a stud from one of my 6g74 heads to see if it threads in, it also threads into the polymer upper


and, my stock 6g72 SOHC 24 valve throttle body bolts to it, so, I could use a 6g74 SOHC throttle body, and with the accommodations from the second picture of the cast in metal parts, I can bolt on a throttle body cable with no welding or brazing (like the MIVEC upper)

anyway, onto the lower intake manifold

this gives the greatest view of the difference in port spacing


if you check back to the image of the bottom of the 6g74 lower, this is very, very similar


the MIVEC fuel rails do also bolt on and fit on perfectly with either the fuel injectors from the MIVEC or 6g74


and the 6g74 lower to head intake manifold gasket perfectly matches the ports from the lower intake manifold

I should make note, this lower and upper intake manifolds are for a none MIVEC 6g75, it is pretty easy to say, at least from these parts, the none MIVEC 6g75 intake ports , the the throat (of the heads) are pretty close, if not the very same as the 6g74 heads
Interesting, indeed!
 

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Discussion Starter · #55 ·
a semi unrelated update

the 12 valve 6g72 is basically the 409 of the 6g7 engine family, it shares very few parts with other members, also the valve covers do have the W type pattern, one of the few parts that appear to be able to be carried over is the 6g74/6g72 SOHC 24 valve motor's rocker arms on the intake side, pictures will follow
 

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Discussion Starter · #58 ·
information to be added soon; 6g72(74) DOHC head+piston and lower intake manifold, 6g72 SOHC 12 valve head+piston and left hand transmission intake manifold, G6(A)U FWD head+piston and upper intake manifold*, additional research into the 6g75 block to also be included. ETA 2 months to the first additon. This thread will ultimately become a database thread of my research into the 6g7 variants and sister families

*mechanical information present for upper intake manifold in The Galant Center and Club3g, I would be focusing on the electrical, I intend on getting an AWD full engine but this is a later date both mechanically and electrically
 
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