3.8 6G75 Swap Discussion

[foxbrand]

I thought for something like this, you would get the lower intake manifold machined to match the heads (provided that they have the block there as well)

[Silvertune]

I guess it's subject to your judgement. I don't believe it is, it holds crank case pressure for years just fine. Just make sure you use enough to seal up the gap and install it correctly and you should be fine. The chances of them being able to actually machine it to match perfectly are essentially zero, since you have two flanges on the same piece mating to flanges on two different pieces the geometry is really hard to get right.

[buddhalawton]

Thanks for the input guys. I got lucky on this one. The original 6g75 lower intake manifold fits the heads perfectly unlike my 6g74 lower intake manifold. I'm sending both intake manifolds to the engine builder. He can match the angles on the good lower to my ported and polished one.

[Silvertune]

Did you ever decide on a throttle body and upper intake manifold setup? That's what's going to determine how badly you choke above 5500.

[buddhalawton]

6g75 non-mivec upper intake manifold, port matched. As for throttle body I'm going with a hand blended 6g74 65mm TB with the half shaft mod and low profile screws. The half shaft mod alone really opened up a lot of room in the bore.

[Silvertune]

Been doing that to throttle bodies for awhile now. Very good mod. You would benefit hugely with a real 70mm but you'll do as good as possible with stock.

Make sure you replace all the seals too so long as you're in there. They all leak...

[buddhalawton]

Done and done. Had the IAC overhauled and tested. New Mil Spec shaft seals just came today. Thanks.

[Silvertune]

The mil spec shaft seals won't fit perfectly, the bore in the 72 throttle body is tad bigger and deeper. However if you have a dremel and are good with it you can pull the bore out a tad and since the washers that cover the seals are fiber they will sit over the steel case just fine.

[buddhalawton]

I'm using the 6g74 throttle body.

Here is a pic I took while overhauling it.

[Silvertune]

You didn't install that correctly. It has to fit down into the recess that the stock seal came out of and there is no physical way to do that with the rubber side down since the bore is smaller than that of the metal casing. I've done this install on some 15 throttle bodies...

[buddhalawton]

(DELETED POST - INCORRECT INFO REMOVED)

[Silvertune]

Provide more pictures of different angles. I'm not saying you're wrong but I know for a fact I am not. What was the diameter of the seals you got?

[buddhalawton]

I see what you're saying Silver, the new milspec seals don't sit exactly flush against the tb body when they are seated. They fit snugly into the ID but do stick out approx .41mm (.016) when they are seated in the throttle body. Multiply that by 2 seals you have almost 1mm of total extra width. This will cause issues with the TPS, throttle plate installation, etc.

I will definately modify the TB housing to allow the seals to sit perfectly flush with the body.

Thank you for your help and patience. I'll edit the above posts to correct the info.

[Silvertune]

Not a problem Brett.

Remember the two washers that sit over the seals are fiber washers and they can soak up a small amount of space. Just make sure you lube everything well because it does get a bit stiffer and you should be good to go.

[foxbrand]

Originally Posted by Call Me JZ

What would you like to know?

sorry for the late term revive on this


anyway
would there be any real affect on flow from machining the combustion chamber? I know (this is what I'm referencing to be machined out) there are little triangle off shoots between the intake and exhaust valves that I can only guess is there to create tumble within the combustion chamber, would removing these specifically reduce valve shrouding?

[alacarte]

Question about 6g75...

I know rear 6g75 stock manifold don't fit in engine bay (firewall clearance)
Can I use stock 6g74 exhaust manifold without cat ?

Thanks for your help !

[Fenix22]

Originally Posted by alacarte

Question about 6g75...

I know rear 6g75 stock manifold don't fit in engine bay (firewall clearance)
Can I use stock 6g74 exhaust manifold without cat ?

Thanks for your help !

Yes. Any 6g7* exhaust manifold will fit. 3g eclipse & diamantes are the most common exhaust manifolds used. cali & fed will work, depending on which one it may have extra 02 sensors holes or not.

[Mattt]

Some of you may have seen this already, but I thought I'd share:




MIVEC 6G75 teardown...lots of pics - 3000GT/Stealth International Message Center

[dankcincy]

Holy hell what a read!!! After 4 days of off and on reading I finally made it to the end.

And after all that reading I have a question.

Why?

I guess that Im completely missing something because I cant see putting that kind of time, money, and energy into something that is only netting 20 or 30 hp over the advertised power of the stock 72 in the Strat.

I get that there is a coolness factor and a "because I can" factor but arent there more efficient uses of cash flow to get power under the hood of these cars?

From what Im seeing you guys are talking thousands of dollars and countless hours for what Im seeing as a minimal return on your investment.

As cool as it is I must be missing something.

[buddhalawton]

Exactly why I dumped even more money into machining, fuel system, and head work.

[chavezeclipse]

with aftermarket headers, intake, exhaust, a good tune you should have closer to 250 to 260 at the crank maybe even a little more. cams help a lot with the build as well but if you want 300hp you will have to dump lots of cash regardless either it be a built 3.8 or FI. you have to pay to play.

[dankcincy]

So I forgot that the advertised is at the crank, Its been awhile...sue me.
I havent looked at the performance side of the strat since 06 and then there didnt seem to be much going on with it so I backed away.

Now there seems to be tons of info which is awesome!!!

[dankcincy]

Originally Posted by chavezeclipse

you have to pay to play.

I totally get that but is the 75 the much better of a platform then the 72?
Something that I didnt see (and yes I read the whole thread) was the weight difference between the two setups. Yes I could of missed it (Ive only read through it once) but didnt see it in here.

[dankcincy]

Im just starting my research on this again since the strat is getting up there in miles and the swap seems a viable option if I can justify it. If I remember correctly some of the main benefits would be a longer stroke giving better torque and better flowing heads?

Thank you to everyone that figured all this out. As I could see it took a long time and a bunch of cash to get it to where its at.

[Silvertune]

A fully bolted on tuned 72 will run you 14.8. A fully bolted on a tuned 75 will run 13.5. Make sense?


And where are you getting your $ numbers from? I'm half way through doing this swap on a GTS and it's got maybe 2k into it total.

[chavezeclipse]

yes. the 75 compared to the 72 comes with larger throttle body (that you cant use since its DBW so get a 6g74), higher flowing intake manifold, higher flowing heads, larger crank, longer rods, larger pistons. i mean a lot if different. even the 6g74 is swap worth looking into but for power do the 6g75.

weight difference is like 50 lbs heavier. throw your battery in the trunk and you wont even notice the difference in handling then (i swapped a 6g74 and at first it threw handling off, to me anyways, moved battery to back fixed that)

[Silvertune]

I did prothane FLCA bushings with the big block and it handled BETTER.

[dankcincy]

Originally Posted by Silvertune

A fully bolted on tuned 72 will run you 14.8. A fully bolted on a tuned 75 will run 13.5. Make sense?


And where are you getting your $ numbers from? I'm half way through doing this swap on a GTS and it's got maybe 2k into it total.

Those are nice straight line numbers but straight lines bore me. Besides it only tells part of the story.

Thats exactly what Im saying, youre only half way through and already have thousands into it. I assume all the major pieces have been purchased which is where the money has gone. Now its just the nickle and dime stuff left?

[dankcincy]

Like I said, Im just researching at this point to see if its even worth the time and energy. I like the idea of having a better base to work with which is why I spent the time here.

[dankcincy]

Im just looking to get a 10:1 +10% power to weight while maintaining the handling. I really dont care how I get there.

[Fenix22]

If you're going to be replacing the engine and wouldn't mind more power, the 75 should be considered. Since you'll be buying an engine either way you're already going to sink a grand or so into the project. Get a 75, then you can sink enough for the exhaust, be it headers or custom downpipe on stock manifolds, and enough to get it tuned. That's where most of the money goes. Other things are just misc stuff and other things you need for the swap, but it's only bits and inexpensive pieces.
Should I ever replace a 6g72 in another 3g eclipse, a 75 replacement will be considered.

[Silvertune]

Time for a little summary, no more retarded questions evolving out of misinformation.

Parts REQUIREMENTS for the 6g75 Non Mivec Swap (subject to upgrades of course):
6g75 Non-mivec motor

Custom air intake: best bet is to make your own. Use 3" piping and a 4.5" MAF flange with dry flow filter. This is the cheapest and most effective method.

6g74 throttle body; (even this is too small for the motor so don't even think about using the 60mm) TPS is plug and play, IAC pigtail needs transplanting, otherwise just pay attention to the vacuum setup

Upper manifold options:
6g74: bolts on the same way it always does but it's a crap manifold compared to the second option

6g75 non mivec: bolts on but requires trimming the hood above the left front corner of the runners and a throttle body flange transplant or adapter to fit the 74 throttle body without leaks. Cruise control on the 74 throttle body fits under the hood with this manifold if you clear away a small piece of bracing. Flattening out the right edge of the battery tray allows you to retain stock battery location as well. This manifold nets a solid 15whp 15-20wtq over the 74 manifold and sounds better. Very worth it.

6g74 lower manifold - use 6g74 or 6g75 injectors they fit the same, just note for tuning
6g74 fuel rails with spacers
6g72/6g74 fuel pressure regulator (supports full bolt ons and tune with stock pump)
6g72/4 crank position sensor with reluctor wheel
6g72 distributor with 6g72 wire set (NGK's fit, 74 distributor will NOT work)
6g74 upper power steering bracket
6g72/4 lower power steering bracket
6g74 lower timing cover (PS belt runs through the plastic degree tab on the 75 lower cover, you can either use the 74 lower cover or shave the tab off the 75 lower and seal it up epoxy or tape)
6g74 alternator bracket
6g72 AC bracket (same as 6g74 bracket)
Shaved axle bracket (same as 6g74 swap)
6g74 coolant housing - with thermostat of course and both coolant temp sensors, stock radiator hoses work fine, one of the heater core hoses will need shortening
Stage two Clutch: (stock will not handle it)
Exhaust: covered at the end of post

TUNING - this is requried, you will blow it up running it without tuning. Besides that you'll make 6g72 output as well.

Highly recommended upgrades:
Lightweight flywheel (more power, sacrifices nothing and helps keep your drivetrain happy due to less rotating momentum)

Limited slip differential (The stock diff is easily cracked with the 72 and a higher stage clutch, if you beat on this motor with a higher stage clutch the stock differential will break eventually)

Urethane driveline mounts - all of them. This is basically a requirement, the stock motor destroys stock mounts, the 75 will blow them out almost immediately and in the time it takes it will shake and cause massive amounts of wheel hop. The latest Prothane kits come with all four bushings and K member bushings too. They no longer produce bushings with relief holes so they are stronger. The energy suspension kit comes with the front and rear mounts and K member bushings and are much stronger than even the latest prothane set but don't come with side mounts. For best results you want to upgrade all 4 mounts and the K member bushings, any combo of the two kits being sufficient.

Torque damper - by no means a replacement for the engine mounts, it is essentially useless without urethane mounts but it is HIGHLY recommendable to use WITH the urethane mount upgrade.

Urethane front lower control arm bushings - the FLCA bushings are just like the motor mounts, soft and easily destroyed. Upgrading to urethane will help you stick bigtime and help eliminate wheel hop. Prothane makes a set for early control arms (some early 00 build dates), energy suspension covers the rest of the years. Clarify which you have before purchase, late model arms have a nut on the end of the pin that sits in the large bushing. If you have this, buy the Energy Suspension kit. If drive an 00 and your arms simply have pins sitting in the bushings get the Prothane kit.

With all urethane engine mounts, torque damper and urethane FLCA bushings you can hook at least 260wtq in second gear with crappy tires. I have done this on 3 cars now, two of which had the open differential.

Other options and notes:
6g74 oil pans (both pans with dipstick, dipstick tube, pickup tube and baffle) - bolts up to the 75 almost entirely, two bolt holes won't line up for the upper pan to block surface but so long as you're liberal with RTV this won't produce an issue. With the 74 pans you can fit any header setup that fits on the 6g74, the 75 pans are a bit wide/deeper so you have to modify even some 6g74 stuff to fit.

6g72/6g74 side mount bracket - the 75 bracket has an extra mounting point on it that needs grinding down to fit the AC bracket. That or grind the AC bracket, either works.

Valve covers - any front or rear covers for the 24v SOHC will bolt up but there are a few things to note.
They all have the same timing marks so no worries there
To use the 6g75 upper manifold the 6g75 rear valve cover is required. The 75 upper manifold cuts off the rear PCV port on other valve covers which WILL results in blown valve cover gaskets and oil cap leakage.
The 75 front cover has a threaded PCV valve as the Chrysler 6g7 covers do and brackets for coil packs and the 75 engine cover if applicable. The front valve cover is otherwise a visual choice. Wording and engine cover choice are worth considering here.

Cam gears; all 6g7 24V SOHC cam gears are identical. That said should you so break one or desire an upgrade those for the 72 or 74 work also.

Accessories: You reuse your stock power steering pump and AC compressor. The stock alternator usually reused as well however the 6g75 alternator CAN be used if you so desire. It is a 110 amp as opposed to 90 amp stock. Doing the swap with the 74 power steering and alternator brackets allows you to reuse stock serpentine belts as they are the same length as on the 74.


EXHAUST CLARIFICATION
The 75 makes good use of a 2.5" catback, you WILL SEE GAINS using the 2.5 or 3.0" over the stock 2.25 system. They make no difference on the small motor but the 75 is capable enough to put these diameters to use.

Headers: 6g72 header setups will need modified downpipes to fit on this motor. If your setup fits a 74 then it will fit this motor if it is clad with 74 oil pans, however not all 74 setups will fit over the 75 oil pans either. In any case, expect to modify things to make it all work unless the setup is coming off another finished 75. RPW headers both long and short tube bolt onto this motor without modification.


All this aside do yourself a favor and do all your maintenance now. High quality timing belt kit with hydraulic adjuster and water pump, thoermostat, spark plugs, wires, cap and rotor, and anything else you think would be good to put in now.

[buddhalawton]

Long time coming.

http://www.club3g.com/forum/group-bu...ml#post3361883

[z80]

For those interested in twin turbo on a 6G75...

Got mine in and running at last.

Very first dyno run it made 255 kw at the wheels (340 hp) and 700nM of torque.

Wait for it....that's at 4000 rpm.

She was running out of fuel so the single ended non return fuel rail needs extra work.

Should be sorted next week way too peaky on the road at the moment.

Here's a few pics for anyone interested.









]



















perfectly symmetrical pipe lengths.



factory hot dog silencer strategy retained, but with new units.



exhaust gas crossover joint and flexible exhaust couplings



passenger side intercooler piping, fully concealed behind bumper bar



Spot the hidden black powder coated modified Subaru WRX intercooler?



Both turbocharger unit intakes come from the rear of the modified stock air filter box.



Modified throttle body intake piping.



custom fabricated Y pipe for merging two turbo intake pipes

[thahnic1080]

at what psi? Turbo size?

[z80]

Originally Posted by thahnic1080

at what psi? Turbo size?

12 psi,
dual Garrett GT2560 turbos,
Walbro fuel pump,
600cc Siemens injectors,
custom refabricated WRX intercooler.


She starts and lives....

http://youtu.be/HTQWvAT4Vx0

[z80]

Custom fuel regulator being calibrated with a bit of dyno work.

Mitsubishi 380 twin turbo - YouTube

[nightblade897]

Originally Posted by chavezeclipse

yes. the 75 compared to the 72 comes with larger throttle body (that you cant use since its DBW so get a 6g74), higher flowing intake manifold, higher flowing heads, larger crank, longer rods, larger pistons. i mean a lot if different. even the 6g74 is swap worth looking into but for power do the 6g75.

weight difference is like 50 lbs heavier. throw your battery in the trunk and you wont even notice the difference in handling then (i swapped a 6g74 and at first it threw handling off, to me anyways, moved battery to back fixed that)

What about the 90mm TB? ;)

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[chavezeclipse]

IMO not worth the hassle but if you want to go for it

[nightblade897]

Originally Posted by chavezeclipse

IMO not worth the hassle but if you want to go for it

I was thinking about it. Tho idk if the plenum inlet can be ported that big. Idek wat size the 75 has...

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[foxbrand]

you need an adaptor to use a q45 throttle body on a 6g75 upper intake manifold

[M-Rod]

even then, it wouldn't matter because you're still limited to the opening of the flange on the intake manifold.

[nightblade897]

Originally Posted by M-Rod

even then, it wouldn't matter because you're still limited to the opening of the flange on the intake manifold.

Thats what i was refering to when i said idk how much you can even bore it out... i mean you could always chop off the flange and weld a new one on thats fitted to the q45 but that might not even fit. What i took some 45 degree 90mm aluminum piping welded in place with the q45 flange... then it would be worth it!

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[Silvertune]

Not really... The inlet on the manifold is 70mm and it stays so all the way into the plenum. There is no way to make it an 80mm bore through so a throttle body of that size is useless.

[chavezeclipse]

there is no problem with the 65mm. i mean you have other things limiting airflow far more than the throttle body size

[nightblade897]

It was just a sugestion thats all.

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[Silvertune]

With the appropriate set of bolt ons and a little top end pampering the limitation is the cams. Given a set of aftermarket cams and you'll want a 70mm at the very least.

The problem is no one nuts up and buys cams so there really is no need to look further than the diamante throttle body with a flange correction.

[TurtleTamer]

I went today to pull a '75 from an '04 Galant that was wrecked in the front and driver side. To my horror the bell housing was broken and upon further investigation I found the upper oil pan has a hairline crack in it as well.

I couldn't even spin the motor because there was no way to get the trans in nuetral. Do you guys think this has a high liklelyhood of having a bent crank or other damage? I hate to let this awesome deal on the motor go but if it's bad I don't want to jack with it.

I figure if nothing else I'll grab the cams out of it for the future.

[fast gt]

You won't be 100 percent, if you can get it in neutral, turn it by hand

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[TurtleTamer]

I can't get it in neutral. If I get this thing I'd have to replace the oil pan which is ok since 74's are fairly plentiful around here, but I'm wondering if there is any way to check this sucker before I buy it. I can get it out of the car and see if it'll spin then, but it may be hard to tell of the crank is obviously bent or not. It won't be on a stand either so I'm not going to be pulling the pan and girdle in the yard.

If it IS in fact bent, can it be straightened by a shop?

[chavezeclipse]

pretty sure you can use 74 rods in a 75. they handle more power as well

[foxbrand]

correct

and you can use a 6g75 crank in a 6g74 block with the 6g74 rods and 6g75 pistons (with the cylinders bored out), this has been done before

[TurtleTamer]

I figure as long as I can't see any wobble in the flywheel or harmonic balancer once it's out and spinning by hand, it may either be straight or correctable. I'll also be able to see what the input shaft looks like. Sorry to put this in this thread guys. God knows it doesn't need any more clutter. I didn't really know where else to put it and didn't want to start a new thread.

[Silvertune]

Cracked bellhousing is worrisome. Flex plates don't typically hold much planar rigidity but if the oil pan is cracked it was hit pretty hard. Could've put even the slightest bend in the crank which would effectively ruin it. That said, depending on what you can get the engine for, it would probably still be worth a buy so long as you acknowledge the project nature of the engine.

[nightblade897]

You dont happen to live near cleveland ohio do you?... cause theres an 04 up there i wanted to go look at with driver side damage aswell...

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[M-Rod]

Originally Posted by foxbrand

correct

and you can use a 6g75 crank in a 6g74 block with the 6g74 rods and 6g75 pistons (with the cylinders bored out), this has been done before

and how well did that work out compared to an actual 6g75?

[TurtleTamer]

Well everything seemed in order, so I picked it up. hopefully it turns out ok but for $240 I will not complain.