Need More Info On V6 DOHC Swap

[Boosted]

I have searched for info, but I need to know if the Hyundai 3.3 or 3.5 motors will work. I know about that with either the '74 DOHC or the Hyundai motors I will have to use a standalone. As far as compression, which motor is the best for boost? And with the Hyundai motors, can I still use the 3G manual tranny?

Also, I have looked into performance parts for the XG350 and have had no luck so far. So even if the motor swap is possible, does anyone know if I can use the 72/74 headers, cams, etc?




Any help is much appreciated.

[DTP]

I would go with 3.5/3.8 out of the eclipse

[Boosted]

I wanna do something different, I have pondered about doing the 75 swap but there are already guys that have done it. This is something that no TGC member has done (to my knowledge).

[SPD_FRK]

I wanna do something different, I have pondered about doing the 75 swap but there are already guys that have done it. This is something that no TGC member has done (to my knowledge).

Though the DOHC swap on the V6 would be different, it doesn't come without some major items that need to be dealt with.

The DOHC engines run on a distributorless ignition system unlike what is used on the 3.0L 6g72, and 3.5L 6g74 (Diamante, not the Eclipse) engines. This will require nothing less than a standalone to control the ignition system.

The other items you need to consider, or hopefully have from your research is that the DOHC heads are not much better than the 6g75 heads (which btw even the 3000 GT community has found serious benefits of).

The reason the 74 swap was so popular for the Galant and Eclipse is because it was a step up from the stock 6g72 engine. The only downfall on the 6g72 and 6g74 engines are the heads. This is where the 6g75 became the new choice for the Galant, Eclipse, and 3000 GT communities because it has much better potential.

We already know that the 6g72 engine, if built, can handle boost well and has the potential for somebody to make big numbers with it. The same goes for the 6g74, and the 6g75 being built for boost. You really don't want to just swap in an engine without doing a full tear down and running some forged pistons (choosing your desired compression ratio).

Really, building a 6g74 or 6g75 for boost on the Galant would be different, nobody has done that yet. We have setup a lot of the "leg work" for the V6 community (both the Galant and 3rd Gen Eclipse) to run and tune a boosted setup via the EcuFlash, the Galant just needs to swap to an Eclipse M/T ECU (intermediate harnesses are going to be available for this soon).

As for the manifolds, you are pretty limited at this point to a cusotm set being fabricated for a turbo configuration. "Pharmicis" makes a turbo system for the 3rd Gen guys, but personal opinon of the design, it's not the best setup and a more efficient design is possible.

You can't use the SOHC cams in a DOHC cylinder head, might be a mis-type on your end, but want to make sure that is covered and clarified.

[Boosted]

I did some research and know that I must use a standalone and I am building this motor from top to bottom. Everything in and on the motor will be aftermarket. Can u give me the compression ration for the SOHC and DOHC 74 motors and the DOHC Hyundai motors?

[SPD_FRK]

I did some research and know that I must use a standalone and I am building this motor from top to bottom. Everything in and on the motor will be aftermarket. Can u give me the compression ration for the SOHC and DOHC 74 motors and the DOHC Hyundai motors?

Fair enough, just making sure everybody gets the best information on this engine series.

The 6g74 engines I believe are 9.5 or 10:1 CR for both the SOHC and DOHC heads. The stock CR won't matter at all though since you are rebuilding the engine so that isn't really anything to be concerned about.

CP may have the specs on hand from boostzealot's set of pistons from his 6g74 build, otherwise you may still be required to send in a stock rod & piston combo to them to get all the data they need to make you a set. Ross is another outlet for pistons as well and would require the same basically. If they do not have the measurements from previous piston sets, be prepared to spend a bit more money. The 4th Gen folks had Ross make a set last year and that ran $1100, they are now priced at $730 without the rings.

If you are doing a full engine buld make sure you get the crank balanced, pointless to build an engine like this and not balance everything. In regards to the bearings you will want to look for ACL bearings for the 6g74, do not bother with the cheap Clevite or OEM bearings.

Hopefully you either have the money on hand for this type of build, or the time and patience to complete it, but be prepared for this to run close to $4-5K quite easily.

[Boosted]

Oh I have at least 3K in hand at the moment, but it will be a slow process seeing as how I have a daughter and wife and I am still finishing the build on my 2G Eclipse.

[mko]

Dont quote me on this, but if the 3000gt guys use the 3.5L block then you can swap the 3000gt DOHC heads over, It will only need a custom intake manifold. And of course you gonna have the rear head up front and the front head in the rear, if you know what i mean. And then get a machine shop to machine the distributor to fit the DOHC head cam sensor hole.

Just an idea

[SPD_FRK]

Dont quote me on this, but if the 3000gt guys use the 3.5L block then you can swap the 3000gt DOHC heads over, It will only need a custom intake manifold. And of course you gonna have the rear head up front and the front head in the rear, if you know what i mean. And then get a machine shop to machine the distributor to fit the DOHC head cam sensor hole.

Just an idea

You do realize the firing order is different on that particular engine right? Also, the engine is mounted 180* opposite of the Galant/Eclipse 6g72, thus engine rotation is opposite...not sure how you feel about it, but me personally would never even think about doing that type of head swap. Not a fan of running cam timing in reverse at all...

[mysticj]

Use either the 98/99 3KGT ECU or the 98-03 Montero ECUs for DIS ignition. The Monteros have an intergrated TCU like the 8G ECU and ECU harness is almost the same as the 8G.

[Boosted]

This is great information, it will be a good amount of time before I get the motor and begin the build process. But, I want to have all the right information before I begin.

[mko]

You do realize the firing order is different on that particular engine right? Also, the engine is mounted 180* opposite of the Galant/Eclipse 6g72, thus engine rotation is opposite...not sure how you feel about it, but me personally would never even think about doing that type of head swap. Not a fan of running cam timing in reverse at all...

LOL, ok I know you're doing these crazy swaps and all, and I mean no disrespect, but I guess you dont understand the concept of mounting the engine on 180* opposite.

All mitsu engines spin in a clock-wise direction, all of them regardless where they are mounted. For example, the 6g72 in a 3000gt spins from front of the car to back(clockwise) and the engine is mounted on the right side of the engine bay.

The 6g72/74/75 in 8g Galant, Diamante, Eclipse spins from the firewall to the front of the car direction which is still clockwise, but looked from a different angle because the engine is mounted on 180 deg opposite. So there's no reversed timing or anything like this.

So installing DOHC heads is basically the same as getting a 6g72 DOHC engine off 3000gt and flipping it 180 degrees and mounting it on the opposite side of the engine bay. With this configuration the intake manifold will end up right next to the radiator, so that why I said it needs a custom manifold.

If he uses a machined SOHC distributor mated to the DOHC cam, the firing order will be exactly the same as before.


Its the transmission for 3000gt's and the older style engine layout that has that gear on the intermediate shaft that flips the rotation at 180 deg. The 3g V6 trans dont have that gear and the crank motion is directly transferred thru the gears and the output shaft to the wheels. In fact, the theory says that if you install a 3000gt trans on v6 Galant, you'll end up having 5 reverse and 1 forward gears, perfect for high speed chases in reverse...lol

[SPD_FRK]

LOL, ok I know you're doing these crazy swaps and all, and I mean no disrespect, but I guess you dont understand the concept of mounting the engine on 180* opposite.

Well I will stick my foot in my mouth then, by all means then do the swap.

Believe me, I do "understand the concept," you just need to realize that like you, I also make mistakes sometimes.


Enjoy the build, and good luck to you with everything.

[Boosted]

Something else I need to know, with the XG350 motor are they any 74 or 72 parts that can be used such as headers, intake manifold, or other bolt ons?

[mysticj]

Something else I need to know, with the XG350 motor are they any 74 or 72 parts that can be used such as headers, intake manifold, or other bolt ons?

headers...anything 3KGT N/A or Turbo
intake manifold...gutted XG350, 3G GTS plenum on the XG runners, or 6G75
cams....Azera?, Amanti, any 3KGT DOHC aftermarket cams

that's all i can think of...u will need to check for bolts on from the 3KGT.