6G74 -Stroker/4.0L Information

[SPD_FRK]

This information has been floating on Club3g since 2008. Not sure if much, if any of it has been posted over here. I think this community has started picking up on the 6G74 swap a little more lately, and some may not be aware of the performance possibilities just yet.

For those of you who have done the 74 swap already, feel free to get in on the discussion, help others looking into it, and keep looking ahead as we are not limited to just the 6g74 swap anymore.



You can use a 6G74/75 block for this build. The 6G74s are easy to find, and they are inexpensive. THose currently with a 74 swap can swap in parts also. The "ultimate" choice, though more expensive is finding a complete 6G75;
6G75 Deck height 228
6G74 Deck height 228

6G75 Bore 95
6G74 Bore 93

6G75 Stroke 90
6G74 Stroke 86




Crank
The crank out of the 3.8L 6G75 is a direct drop in replacement for the 3.5L block.
6G75 Main journals 64

6G74 Main journals 64




Rods
6G75 Rod Journals 55

6G74 Rod journals 55



Though similar rods are used in both the 6G74 and 6G75, there is one vital difference. The rods you will want to use for this build are the rods from a 6G74 as they are much thicker than those being used in the 6G75 engines.

6G74 Rods


6G75 Rods




Pistons
The bore needs to be taken from 93mm to 97mm. That's a 4mm overbore.The pin downset will need to be changed from 31.75 to 29.75 in order to achieve the full stroke movement of the 6G75 crank and rod/piston combination.

6G75 Wrist Pin downset is 29.75
6G74 Wrist Pin downset is 31.75



Heads
6G75 Head (both Mivec and non-Mivec) are a direct bolt on. The Mivec and non-Mivec heads have their pro's and con's, as the Mivec heads have an intake port similar to the 1G 4g63 heads while the non mivec have ports similiar to the 2G 4g63 heads. The Mivec heads will require an external switching system/controller to operate the MIVEC system.

MIVEC Head Shown;


Non-MIVEC Head Shown;



The 6G75 head has a 65cc combustion chamber, compared to 43cc of the 6g72/4 heads. Doing just a 6G75 head swap will lower compression alot, so you will need to account for this with aftermarket pistons to get your desired compression ratio.


The best heads to use on any 6G74 swap are the 6G75 heads because they have larger valves, and unmodified 75 heads will outflow a set of PnP'd 74 heads by nearly 18%;



Cams
Aftermarket cams for the MIVEC heads are still waiting for production, but at this time the best choice is the non-Mivec heads. You can swap in a set of RPW cams for a 6G72/4 into the non-Mivec heads. You can still use the aftermarket cam gears from a 72/74.



A build such as this, paired with other items is easily bringing the reality of 300+WHP numbers to us now...

[Ruslik]

nice find

[Boosted]

Interesting....well it looks like my idea might have some potential after all.

[Ivory8g]

good thinking on bringing this over here!

[Galantfan88]

Great info man

[SPD_FRK]

Interesting....well it looks like my idea might have some potential after all.

What do you have in store if you don't mind sharing some information? We all have little secrets, just figured too much information is withheld that others can't learn or are too afraid to take on some of this stuff.

Heck just to show some of my build information this is what I have in store;
Full 6G75 non-mivec swap
Ross or CP pistons
N/a compression (11-11.5:1), or if turbo, 8.5-9:1 to prevent from being a dog with the big turbo I would plan to use
RPW valves
RPW Cam
Swap in 74 rods (on their way as we speak)


I would assume you are going turbo though? If so the 75 heads, even on a regular 6G74 block and crank would still produce some great power. I think a lot of people (including myself) were not even aware of the 75 heads, MIVEC or not, even fitting on a 6G74. Given the flow chart information above that was posted anybody can clearly see the 75 heads would be the optimum choice for any build, turbo or N/A...plus we can still use the 72/74 valve covers so that even if you pop the hood people wouldn't know any different unless you told them.

good thinking on bringing this over here!

Definitely! I know some people like to hold back information on their builds or whatever, but I hate that. Everybody has some things they will keep hidden, but with stuff like this out there, it would only be holding back others on this platform from getting any farther.

[4g63lover]

Oh man, here we go. You are a BEAST Matt!

Good info!

[SPD_FRK]

Oh man, here we go. You are a BEAST Matt!

Good info!

lol...There is information like no tomorrow on here for the 4cyl platform, so it was time the V6 platform got some much needed information and "motivation" to start building too.


I am waiting for beam to get in here with this lol

[mysticj]

Matt, the 6G75 have a head cc of 65 compare to the head cc of the 6g72/4 of 43. So a 6G75 head swap will lower compression alot.
Also, the Mivec heads and non-mivec heads have their pro's and con's, as the Mivec heads have an intake port like the 1G 4g63 heads while the non mivec have ports similiar to the 2G 4g63 heads.

[SPD_FRK]

Matt, the 6G75 have a head cc of 65 compare to the head cc of the 6g72/4 of 43. So a 6G75 head swap will lower compression alot.
Also, the Mivec heads and non-mivec heads have their pro's and con's, as the Mivec heads have an intake port like the 1G 4g63 heads while the non mivec have ports similiar to the 2G 4g63 heads.

Thanks for the additional information. I am going to add it to the original post with some pictures to show the differences

[beam514]

hmmm very interesting. I'll have to look into this more when I'm not half asleep :)

[M-Rod]

This is amazing info. I just may end up putting some of it to use. Thanks! :D

[Boosted]

What do you have in store if you don't mind sharing some information? We all have little secrets, just figured too much information is withheld that others can't learn or are too afraid to take on some of this stuff.

Heck just to show some of my build information this is what I have in store;
Full 6G75 non-mivec swap
Ross or CP pistons
N/a compression (11-11.5:1), or if turbo, 8.5-9:1 to prevent from being a dog with the big turbo I would plan to use
RPW valves
RPW Cam
Swap in 74 rods (on their way as we speak)


I would assume you are going turbo though? If so the 75 heads, even on a regular 6G74 block and crank would still produce some great power. I think a lot of people (including myself) were not even aware of the 75 heads, MIVEC or not, even fitting on a 6G74. Given the flow chart information above that was posted anybody can clearly see the 75 heads would be the optimum choice for any build, turbo or N/A...plus we can still use the 72/74 valve covers so that even if you pop the hood people wouldn't know any different unless you told them.

Planned on a similar build but I have some other options floating around such as 74 heads on a 75 block and stroking to 4.0 or a MIVEC 6G75 swap. No matter what build I persue, I am going for a 4.0 Stroker. But, I wanted to try utilizing the new 6-speed transmission and go with a GT42 or 47 turbo.

[SPD_FRK]

Planned on a similar build but I have some other options floating around such as 74 heads on a 75 block and stroking to 4.0 or a MIVEC 6G75 swap. No matter what build I persue, I am going for a 4.0 Stroker. But, I wanted to try utilizing the new 6-speed transmission and go with a GT42 or 47 turbo.

Are you planning to do larger valves in the 74 heads? Only reaosn I ask is with the flow chart information now shown, the 75 heads would actually be a better component. The price of getting machine work such as a PnP, and larger valves done on the 74 heads would still yield less flow capabilities than the stock 75 heads. Also for a turbo build the larger cc volume in the heads will aid in lower compression ideal on forced induction builds.

If you are looking more into the 6g75 swap, keep in mind the you will need to control the MIVEC and COP. You can ditch the COP ignition and run the 72 distributor though, just requires an adapter plater to be made so the distributor fits;







The 6 speed transmission has an attractive sound to it, but from what I have read so far is they basically crammed 1 more gear into the 5spd range. For a DD it may be ok to use, but you would likely loose some good gearing found in the 5spd variants. Also one other thing to note on a 6spd is that the internals are weaker (basically smaller material) in order to accomodate the extra gear. These components will only hold up for so long, and up to a certain amount of continuous power applied to them before something breaks. The Evo 6spd is a very good comparison on this issue as they have had the exact same issues and are still swapping out to a 5spd.

Until somebody starts making billet internals for these transmissions the 6spd will remain to be a weaker alternative to a 5spd...but even then the billet internals can fail once they reach a certain limit, or start breaking axles and other parts.

[Ivory8g]

^ the man speaks truth!

[Stewi]

This is all great info.

I would like to just throw in my .02 about this topic. While I dont have much experience with any of the V6 platforms, my common knowledge and experience with turbo systems and engine dynamics still can relate to this topic.

The only reason I can see to get a 4.0L engine into this car is if you plan on going all motor and making 400-500whp naturally aspirated. If you did this with the intention of turbo'ing it, I cant really see a huge gain versus just doing a regular 6G74 swap. The 3.5 liters of displacement from the 74' is more than enough to spool any type of turbo you would need on a setup like this. On race gas the Precision 6765's and FP HTA86 turbo's are making 800+whp on 2.0 - 2.4 EVO motors. With that being said the larger displacement of the 74' would be more then sufficient to make a setup like that more streetable. It must also be considered that making that much power WILL kill the trans, axles, etc. The V6 guys are actually lucky as their internal transmission components are compatible with the EVO parts. If I were building a V6 trans I wouldnt think twice about sending it off for a performance build. There are more people doing EVO transmissions now then a few years ago. There are builds out there for just about everyones needs. Some places are Buschur Racing, Jack's Transmissions, Shep Racing, DogBox Racing and TRE (Team Rip Engineering). I think it would be a total beast to do an all motor 4.0 V6 setup. Keep posting up info, this is all good stuff.

[SPD_FRK]

Good input Stewi, I am glad to see people are starting to get into the discussion on this more!



Like the old saying goes though, there is no replacement for displacement, and the same is true about turbo/supercharged vehicles as well (Take a look at Intense Racing with their work on the S/c and turbo'd 3.8L). You can run the same size turbo used ona a 3.5L swap, on a 3.8L+ built motor and you may see a little earlier spool up with the turbo due to the increase of engine displacement, and increased fuel...but one thing is it won't be "doggy" until it hits boost either.

Depending on the compression ratio you run, the car may be a dog until the turbo spools, but when it does build boost it it will build power quick and fast (the only thing I can compare the feeling to is a set of compound turbos on a diesel when they spool up, Marc knows lol). For a good street stomper, and a good all around track build I would suggest sticking to a compression ratio of around 8.5-9:1, but keep in mind the boost would likely never get higher than 15psi for a DD...but you would have excellent all around throttle response and great power even up to full boost.


400-500whp N/a, is possible on a Stroker 4.0L engine, but only if you are tuned and running strictly race gas (ie octane of 108+). Running strictly on race gas is not only an additional expense, it also make the vehicle less of a DD and more of a track/race queen only. These are engines running compression ratios of 12.5:1 or higher. Even at 12:1 ratio the amount of fine tuning could allow a person to run on maybe 92octane, or E85 which is a 107 octane.

300-375whp N/a on pump gas is more ideal, and realistic for what most people would want from the platform, unless as noted above the vehicle was strictly built for racing only where pump gas was no longer an option.


The transmission is actually not a major weak link unless you are pushing limits closer to 600+WHP where either the axle shafts snap, or an input shaft in the transmission is just sheered off. I hate to even refercence the member, but even WarmandSCSI was consistently holding a strong 500+WHP on his 5spd transmission as well. Not many people at this time have even hovered near the 500+whp mark because at that point traction becomes difficult and you start looking for AWD possibilites...it basically is not a steetable DD vehicle anymore.

[M-Rod]

Searching C3G, and found more info that may be useful.

EDIT 2: This is all quoted from 3si, they are currently doing a GB for a crank for stroking the 6g74.
"The other option I would be willing to do for this GB, would be the stock 6g75 crank. Thanks to help from Italo Grasso, It has been proven that the 6g75 is a drop in, in the 6g74 block. The same rods are used in both the 74 and the 75. The difference in stroke is made up by moving piston pin 2mm closer to the top of the piston. So, Rays 6g74 stock replacement rods would be a direct fit. I also believe that Ray is working on his custom piston design with the pin downset at 29.75 rather than the standard 31.75mm"

Kinda, the 3.8 6g75 has a bore/stroke or 95/90. The 3.5 6g74 b/s is 93/86. By boring a 3.5 6g74 block 2mm over to 95mm and installing a 6g75 crank, the result would be 3.8L. I'm sure a little bit of clearance work to the girdle and underside of block might be needed, but the 2mm offset increase is minimal, only 0.080". The other change would have to be either the rod length or the downset of the wrist pin location. Your going to gain 2mm of height at TDC, so you either need 2mm shorter rods or the wrist pin has to be 2mm closer to the top of the piston. There are other ways to eliminate the 2mm, but those are the least confusing methods.

[mysticj]

400-500whp N/a, is possible on a Stroker 4.0L engine, but only if you are tuned and running strictly race gas (ie octane of 108+). Running strictly on race gas is not only an additional expense, it also make the vehicle less of a DD and more of a track/race queen only. These are engines running compression ratios of 12.5:1 or higher. Even at 12:1 ratio the amount of fine tuning could allow a person to run on maybe 92octane, or E85 which is a 107 octane.

What about running meth/water injection? I can see a 4.0L Mivec running 360-420whp if billet cams are available with a better IM.

300-375whp N/a on pump gas is more ideal, and realistic for what most people would want from the platform, unless as noted above the vehicle was strictly built for racing only where pump gas was no longer an option.

Personally, I could go 3.9L with an 0.5mm overbore Mivec pistons, XG350 IM with a custom plenum, cams, and q45 TB.

[SPD_FRK]

What about running meth/water injection? I can see a 4.0L Mivec running 360-420whp if billet cams are available with a better IM.

Personally, I could go 3.9L with an 0.5mm overbore Mivec pistons, XG350 IM with a custom plenum, cams, and q45 TB.

Water/Meth injection is another option and is something the company I work for actually manufactures a full system for. They definitely will help cool the incoming air charge and increase the power boost. Systems like that would likely be a track use type situation, or better term I guess would be "limited supply."

Those modifications would easily put you in the mid-high 300whp range. I know some of the 4G eclipse folks on the mivec have pushed out just about 300-305 whp with a tune and simple bolt-ons like an intake, headers, and exhaust.