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Another 3.8 Mivec swap... More fab! Less parts!

117K views 486 replies 65 participants last post by  billyfrancis40 
#1 ·
I guess My fender flare thread wasn't enough to stir the hornets nest... So to really introduce myself, I'm gonna stuff a 3.8 mivec into the stealth.

I was drinking one night thinking about my first girlfriend back in Jr High school.... Then I grew a wild hair up the butt and said, I'm doing the 75 Full Mivec Engine swap. That ends that love story.

It has been done many ways already and I'll be doing this my way. This time around. I'll post up pics of progress as I go along just like the fender flare thread. I know I'm pushing some kind of limit here but it should be interesting to be 4th or 5th known to have done this swap. So far, its Been Itallo, Bdranck, and MichealMR2 that are known to be running Mivecs.

Unicorn engine aquired.




 
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#66 ·
Thanks, I can use all the support I can get. It's not exactly Voo doo but The documentation on the 3.8 as a whole has been lost between 74/75 combos and very in depth big dollar builds. I'm just a normal guy with access to fabrication equipment.
 
#67 ·
Bag=O-Chips said:
The really is no OE solution for making it face the correct direction in a 3/S car.
I've checked every variation on this engine in every market it was offered in. FWD, RWD, Chrysler, Mitsu, Hyundai, Kia. There's just no good option besides cutting and welding.

Best of luck to you. I'm toying around with some 75-based swap ideas myself. I'm trying to sponge up every drop of info I can find.
 
#68 ·
ditto. i've managed to get my hands on a mivec top end to use on a 74/75 stroker, this just adds a bit more complication. maybe extra bosses could be added to accommodate the appropriate 74 neck if it's the proper with, or the mounting holes on the neck itself can be relocated with a bit of creative fabbing (again, if it's the correct width).

or perhaps a 72 neck and the 75 waterneck can be frankensteined together to accommodate.
 
#70 ·
sketch2186 said:
or perhaps a 72 neck and the 75 waterneck can be frankensteined together to accommodate.
That's what bdrank and ItaloGrasso did. They used front and rear parts from the 75 and the the center section from the 72/74. Conceptually it's not that bad, but I'd be worried about finding someone who can weld thick, cast aluminum without warping it.

It sounds like you had an idea similar to one I had though. This will be tricky to explain without a drawing, but...

Assuming the 72 or 74 coolant manifold was the correct width, maybe it'd be possible to make flange adapters that clock everything in the correct direction? You'd basically have a flange that bolts to the 75 head, and that flange would have threaded tabs to accept the 72/74 manifold. You could have a bunch of them cut out on a water jet and sell them to cut down on costs.

The only other thing you'd need to do is extend the length of the coolant pipe that runs down the middle of the block, so the o-ring mates up with the coolant manifold properly.(Since you've now pushed the manifold further off the side of the block thanks to those flanges I'm imagining). That'd be easier to modify than the manifold itself. It might even be possible to use an off the shelf pipe from a Montero. Just from eyeballing it, it might be a little longer.

I'm hoping to end up with some 75 stuff to tear apart for mock-up work in another week.
 
#71 ·
Getting the 75 Coolant housing to work isn't so bad... It just takes some thinking out of the box. All the ancillaries will be added later. The important part is getting the upper and radiator hoses to work.









I'm gonna get this to work :)
 
#73 ·
What block are you using? Since I stuck with 75 everything I didn't have to modify the length of the housing.
 
#77 ·
Not to mention I think it will hit the Mivec solenoid and will also require an extended upper rad hose.
 
#81 ·
This by far is very "out of the box"

So I cut off the section that is pointed towards the firewall... because its not needed and made a template to transfer over to a piece of Aluminium (lol) plate. Need less to say it will be welded on to create a block off plate.


This Little Gem will be the part that allows the 72 filler neck/rad cap to work with the 75 parts. It's part of the peice I cut off the 75 thermostat housing. I threw it in the lathe and turned it down enough for a .002" interference fit into the filler neck.




If you look closely, The piece needs to be radiused to follow the contour of the coolant housing. Once the radius has been done, the hole can be cut out.


In order for the filler neck to fit correctly without obstruction to coolant flow the 75 lower plenum must be trimmed out... nothing a bandsaw and Bridgeport can't handle. The area to be trimmed is marked in Green cross hatching. The green line on the coolant housing shows the location of the dividing wall between the thermostat and coolant passage to the heads, hence the reason for radiusing the adapter/extension to utilize as much area without having to dig into where the separation is.




It's getting good...
 
#85 ·
Here is the upper plenum and lower bolted together. If you note the green cross hatches, you will see the threaded hole is of no use what so ever and is null and void to the sealing characteristics of the gasket and two mating surfaces.


 
#90 ·
Bag-o-chips said:
Not to mention I think it will hit the Mivec solenoid and will also require an extended upper rad hose.
I'd rather extend the radiator hose than do all this AL welding :lol:

Anyway, the 3S upper water fitting will bolt on to the Diamante 74 housing. I already cross referenced the gaskets in ASA.

Unless I'm misunderstanding you, I think the concern would be with it hitting the cam angle sensor. Not the MIVEC solenoid. The solenoid is on what's now the front of your engine.

By the way, did you check to see if a 6G72 thermostat cover will bolt to the side of the 75 coolant housing? Based on some photos it looks like it's just barely wrong, but I can't be sure since I haven't messed with one in person.
 
#92 ·
I'd rather extend the radiator hose than do all this AL welding :lol:

Anyway, the 3S upper water fitting will bolt on to the Diamante 74 housing. I already cross referenced the gaskets in ASA.

Unless I'm misunderstanding you, I think the concern would be with it hitting the cam angle sensor. Not the MIVEC solenoid. The solenoid is on what's now the front of your engine.


Its tight. It may work. Less fab= less downtime
 
#91 ·
I'm not exactly sure about the thermostat housing flanges. I didnt bother since I have a complete 75 with all the fixins. And yes my mistake about the CAS. Either way I found cutting and welding + making one off parts more entertaining. It separates my build from the rest and shows how far ingenuity can take you. Not to mention I don't want to mess with ill fitting radiator hoses when I can utilize off the shelf parts that are direct fit.

I remember my hot rod teacher back when I was still at UTI saying "work with what exists when you can, don't reinvent the wheel because you can."
 
#93 ·
Bag-O-Chips said:
Either way I found cutting and welding + making one off parts more entertaining. It separates my build from the rest and shows how far ingenuity can take you.
I'm all for using factory parts. It's far easier. I think I may have just misunderstood your objectives for this.

Anyway, I'm going hopefully to claim a pile of stuff from a 6G75 Endeavor soon. I'm mostly after the electronics. Let me know if there's any odds or ends you might want from the engine.
 
#95 ·
So I notice that in the above Mivec picture the engine is installed backwards, obviously not a 3S. I've also noticed similar on the 6G74 Diamantes out there.

I'm assuming that Mitsubishi just did that for whatever reason and the engine otherwise fits and rotates the same direction as our engines do? Been thinking about trying to get a DOHC 6G74 from a Diamante for my car since those are easy to find.
 
#96 · (Edited)
Thats not a mivec 6g75 fyi...and that is the orientatin those motors come.

Great swap for 3G eclipses and sebring/avengers as well as 8G galants...people make some good n/a power too. Most swaps i see are non mivec 75s (eclipse 72 stroker essentially.

One in picture is a very sick galany. Its a 74 with 11:1 comp, cams, bolt ons and tune. Last i saw it made about 240ish to the wheels... Ive always thought he should have spent the money on the mivec 75. Much more power potential and bang for your buck. Basically drops in to the 8G+ galants and 3Gs.
 
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