Considering a Slant 6 swap into a Mitsubishi Starion...

[ConStar]

I thought this car was to be a DD for your wife?
Did I miss something?
lol

It's not going to be her DD but she's going to drive it enough where it needs to be reasonably reliable. We do a lot of 2-car tandem trips to car shows, for instance.

The V8 swaps and the 4G63 swap are pretty proven by now and can be made extremely reliable. If you cure the fuel and head gasket issues (which swapping the motor does), the next biggest issue for a StarQuest is probably the universal joints or the torque tube.

The attraction of the Slant 6, first and foremost, was its simplicity and reliability. Now, does that carry over once you start forcing air into it? That's kind of what I'm here to find out (as well as what performance numbers it's capable of).

 

[BillGrissom]

A slant is much longer than the small-block V-8. They offset the water pump and set it into the block, but even then one can't quite fit a clutch-fan, even a thin one from a Jaguar or M-B. If your heart is set on a straight six, the Jeep 4.0L might be a better choice since it lived into the MPFI days (2000's). Only a few people have done MPFI in a slant and very custom. The only way to get EFI w/ bought parts is a 4 bbl intake (Clifford or Offenhauser), plus TBI (many 4 bbl carb replacements). I haven't heard of factory turbo for a 4.0L, so would have to be custom like a slant. I recall the exhaust is on the same side as intake, which makes plumbing easier (unless adding an inter-cooler). Some people love a straight six, like BMW owners who whined thru the years it changed to a V-8 (then brought the six back). But, BMW parts are $$$. If you want a V-6, consider the Mopar 3.8L. It has a better 60 deg V angle than the earlier Magnum V-6. It was used in Jeeps, so there are RWD transmissions and motor mounts, plus Jeep guys degrade it as "minivan engine", which is stupid but may have led some to remove them for a 4.0L.

 

[ConStar]

A slant is much longer than the small-block V-8. They offset the water pump and set it into the block, but even then one can't quite fit a clutch-fan, even a thin one from a Jaguar or M-B. If your heart is set on a straight six, the Jeep 4.0L might be a better choice since it lived into the MPFI days (2000's). Only a few people have done MPFI in a slant and very custom. The only way to get EFI w/ bought parts is a 4 bbl intake (Clifford or Offenhauser), plus TBI (many 4 bbl carb replacements). I haven't heard of factory turbo for a 4.0L, so would have to be custom like a slant. I recall the exhaust is on the same side as intake, which makes plumbing easier (unless adding an inter-cooler). Some people love a straight six, like BMW owners who whined thru the years it changed to a V-8 (then brought the six back). But, BMW parts are $$$. If you want a V-6, consider the Mopar 3.8L. It has a better 60 deg V angle than the earlier Magnum V-6. It was used in Jeeps, so there are RWD transmissions and motor mounts, plus Jeep guys degrade it as "minivan engine", which is stupid but may have led some to remove them for a 4.0L.

Thanks for the feedback. We're expecting to have to do custom piping on whatever motor we use. Even if we use the Mitsu 6G72TT, the turbos on a Stealth/3000GT sit low on the engine and the engine won't fit in a StarQuest in that configuration. The turbo piping will interfere with how the engine sits in the cradle. So you have to build an entire exhaust manifold/flange setup from scratch in order to raise the turbos to the top of the engine. This has been successfully done, so the proof of concept is there.

I have seen some other information about true EFI setups for a Slant-6 car; being forced into a carb or TBI setup would be a deal-killer for sure. The factory G54B in the StarQuest is TBI and that's probably the biggest impediment to performance for the car. You can go from 188 hp to 250-300 fairly easily just by putting on an intake and EFI setup from the Australian-market Magna, with modest additional mods.

If I were to use a non-turbo V6, the easiest thing would be to pull from the 6G series motors Mitsu makes. The 6G75 (from the last-gen Mitsu Eclipse) puts out 263 HP with no turbo. You can use the Montero (and maybe Pajero) transmissions just as you would with the 6G72 and 6G72TT. No cutting needed.

My fallback, from the Mopar world, is a 318. That's been done before, too. I don't know if that car had a turbo kit on it or not (mine would, if possible). Again, the Slant-6 idea is something that has never been tried before and I'd love to be the first to have it. As I might have mentioned before, though, the go-to straight-6 conversion for these cars right now is the 1JZ/2JZ Toyota conversions that can produce 600 streetable HP. But those engines require you to delete the front sway bar from the suspension to make it fit, and that's not my preference.

 

[Slant6star]

Hello all.

I currently have a pair of 1980s Mitsubishi Starion/Chrysler Conquest cars. For those unfamiliar, there is no Chrysler in these cars at all. They're all either sold as what they are (Mitsubishis) or are rebadged as Dodge/Plymouth/Chrysler Conquests, depending on years.

They are factory-equipped with the G54B 2.6L 4-cylinder, TBI, single-turbo Mitsubishi motor found in a lot of forklifts and Dodge Caravans. Many of us in the StarQuest owners' groups end up swapping that motor out. I have a 1988 Conquest with the factory G54B still installed and have no plans to change it. But I have a 1986 Starion awaiting a swap, either to Mitsubishi's 6G72TT (Dodge Stealth/Mitsu 3000GT), Chrysler/AMG's M112 (Chrysler Crossfire) or a Slant 6.

The G54B came from the factory with about 180 hp and 230 torque. It's an odd motor, low-revving and almost acts like a straight six or big-block V8 in regards to power curve. So my baseline for a Slant 6 is that it has to at least match those numbers, and hopefully exceed them.

The one other requirement, given the StarQuest application, is that it must end up turbocharged. I would also strongly prefer it to be converted to EFI. This car will primarily be my wife's and reliability is a huge factor (a big reason I'm looking at the Slant 6 over the 6G72TT, especially).

I'm not saying budget isn't a factor, but it's a secondary factor to getting what I want. Ideally, I would like the motor to compare, numbers-wise, to the 6G72TT in factory trim. That would mean around 250 HP/320 torque at the end of the day. From what I've read, that's pretty doable on this motor.

Where I'm running into trouble is that most of the info out there on this kind of build is several years old now, and light on some of the details (what turbo specifically? what are my EFI options? can I retain an A/C compressor, which is a necessity in the South where I live?). I'd like to hear some general opinions on how to get to those target numbers, and having some idea of a budget would be nice, too. There is also the big issue of a transmission -- it MUST be a manual and I would prefer as many gears as I can get (the factory Mitsu unit is a 5-speed).

In the end, this is going to be a neat build. The Starion/Conquest twins are fantastic cars, great handling with an interior that was ahead of its time. The weight balance and nimbleness are fantastic. This car's ultimate purpose will be more for curvy-road driving than anything else; I'm not a drag racer. The car is about 3,000-3,200 pounds. I'm still on the fence about whether to use the Slant 6 or the 6G72TT, and one big advantage of the latter is I have cleaner transmission options and wouldn't need to modify the firewall. Any feedback is welcome.

 

[Slant6star]

Im the owner of what i call Redneck Edition and no its not a slant 6 it has a 5.2 magnum motor in it

Hello all.

I currently have a pair of 1980s Mitsubishi Starion/Chrysler Conquest cars. For those unfamiliar, there is no Chrysler in these cars at all. They're all either sold as what they are (Mitsubishis) or are rebadged as Dodge/Plymouth/Chrysler Conquests, depending on years.

They are factory-equipped with the G54B 2.6L 4-cylinder, TBI, single-turbo Mitsubishi motor found in a lot of forklifts and Dodge Caravans. Many of us in the StarQuest owners' groups end up swapping that motor out. I have a 1988 Conquest with the factory G54B still installed and have no plans to change it. But I have a 1986 Starion awaiting a swap, either to Mitsubishi's 6G72TT (Dodge Stealth/Mitsu 3000GT), Chrysler/AMG's M112 (Chrysler Crossfire) or a Slant 6.

The G54B came from the factory with about 180 hp and 230 torque. It's an odd motor, low-revving and almost acts like a straight six or big-block V8 in regards to power curve. So my baseline for a Slant 6 is that it has to at least match those numbers, and hopefully exceed them.

The one other requirement, given the StarQuest application, is that it must end up turbocharged. I would also strongly prefer it to be converted to EFI. This car will primarily be my wife's and reliability is a huge factor (a big reason I'm looking at the Slant 6 over the 6G72TT, especially).

I'm not saying budget isn't a factor, but it's a secondary factor to getting what I want. Ideally, I would like the motor to compare, numbers-wise, to the 6G72TT in factory trim. That would mean around 250 HP/320 torque at the end of the day. From what I've read, that's pretty doable on this motor.

Where I'm running into trouble is that most of the info out there on this kind of build is several years old now, and light on some of the details (what turbo specifically? what are my EFI options? can I retain an A/C compressor, which is a necessity in the South where I live?). I'd like to hear some general opinions on how to get to those target numbers, and having some idea of a budget would be nice, too. There is also the big issue of a transmission -- it MUST be a manual and I would prefer as many gears as I can get (the factory Mitsu unit is a 5-speed).

In the end, this is going to be a neat build. The Starion/Conquest twins are fantastic cars, great handling with an interior that was ahead of its time. The weight balance and nimbleness are fantastic. This car's ultimate purpose will be more for curvy-road driving than anything else; I'm not a drag racer. The car is about 3,000-3,200 pounds. I'm still on the fence about whether to use the Slant 6 or the 6G72TT, and one big advantage of the latter is I have cleaner transmission options and wouldn't need to modify the firewall. Any feedback is welcome.

 

[Slant6star]

I happened to see my car on this site and i just wanted to clear the fog on my car its not a slant six it has a 5.2 magnum motor in it. I call it Redneck edition