6g72 SOHC to DOHC swap

[the_flash083]

any one done it before? thinking of doing it pull the DOhc 6g72 out of a 3kgt or a stealth posibly even the TT 320hp 8:1 compression.

[dodgeshadowchik]

i've heard it's very difficult/time consuming/costly. i imagine you'd have to use the stealth's trans, and you'd have to fabricate motor mounts since the japaneese cars' engines are "put in backwards" so to speak. (that is trans sits on passeneger side, not driver's side.) but if you have the funds, anything is possible.

[the_flash083]

it is the same block so wouldnt it mount up all the same? i believe the automatic trans sits osn the right side as well on this engine considering the 3.0 is a mitsubishi sohc engine to begin with. the top end is the only thing thats different if im not mistaken.

[speedyshelby16]

Nope they are very different.

3.0 6g72 block differences

MWAHAHAHAH! yes...indeed....

BASIC 3.0 Questions.......

Twin-Turbo 3.0... (2100LB Car) fun right?

[the_flash083]

thanks i guess it wont be happening then thats way to much work for me O_O

[93droptopbeater]

I know this thread is old, don't bother remarking on the fact, thanks.

The conversion is way easier than these "people" let on. The differences between a Mitsu DOHC and Chrysler SOHC are MINOR. Maybe the pass-side mount, the exhaust and the ECU (maybe TCM) are the main headaches. Remote oil filter may be necessary, though. The Chrysler trannies bolt-up, a 5-speed a543 is ideal... I am trying with a 41TE, with Mitsu electronics. My donor car is a 94 3000GT SL, non-turbo.
Chrysler and Mitsu auto trannies are very close, same fluid, too. Mitsu has a countershaft for the reversed engine orientation. OD, TC lock-up, SSDD.
With a Mitsu ECM it should be relatively simple. Might have to play with the wiring a bit, maybe weld a motor mount for the pass-side... no worse than converting to an a543 5-speed from an A/T, REALLY!
It can be done with Chrys ECM, just the ignitions and IAC systems are different. Mitsu has a 60mm throttle body, why waste it?
As an alternative to the DOHC, the '92-95 or 96 Diamante Wagon used a 10:1 SOHC with bigger cams (262 vs 258 degrees). Remote mount oil filter and it should bolt right into a Chrysler (ok, Dodge). The Chrysler intake is a beast, too... I hate to part with it for the DOHC's system... but, oh well. Cross-ram vs "tunnel" ram. Viva la Mopar!
A friend of mine found the remains of an OMNI that had been converted to a VR4 drivetrain... We have it easy in comparison. Take heart!!!
Be Cool!

Beater

[lookin]

great post imo

[speedyshelby16]

I think we need pics of a the vr4 omni

[Ondonti]

The comments you do not agree about regarding compatibility are 100% correct
the blocks are different.

That is not the same question as swapping an entire setup though which is the point of this thread of course.

If I could get my hands on a vr4 drivetrain I would be working on installing that and turning my motor backwards but thats not something easy to get ahold of.

[Shadow24V]

if i could afford the 1000-1500 that people want for the AWD tranny, then get the rear end and center diff, id be doing the same thing. however, if you have the whole motor it is FEASIBLE to swap the whole thing in. i fit the 24v SOHC in a P-body already so....

[LeBeercan_conv]

Yep, those conversions are not as hard as people claim. The DSM peons claim it's hard to convert from 4g37 to 4g63 (or Hyundai 4g67) - but it's not. Brainless swap, for real.
3.0 Chrysler to DOHC Mitsu is a matter of ECMs and trannies. With an a543 or a670, it's 3rd grade math simple. A604 "can" work, a matter of sensors and agreeing ECM/TCM. May have to get fly with the pass/side mount (the one to front of block). Mitsu mounts are better, ANYWAY. Chrysler 3.0 mounts are a sad JOKE. If you have one, you KNOW it.
Exhaust is no worse than a 24v SOHC conversion (24v shadow?). The upsides: DOHC has a steel crank that you probably CAN'T kill and the heads flow better than 4G63s. Not to mention a REAL 10:1 CR (N/A) and MUCH BETTER cams. Killer DIS ignition, too. The 24v SOHC (6g73/2.5, anyway) is cammed different from front to rear head, well known to have high EGTs and FRY pistons - even without ANY power adder. 106 on one head, 108-110 on the other... who came up with that? Benz?
A604 "can work," a543 is the best option, a670 is probably the strongest (BY FAR) but it's a "true" torqueflite and has to be treated as such (treat it as a TF904).
Anyway, congrats Shadow24v! I'm doing the swap (albeit DOHC), looking forward to talking it over with this 'community' during the process.
Happy Thanksgiving, eat well, my friends! Be Merry!

LeBeercan

[Tim_K]

I've heard of people running the stock cast crankshaft to 1100 hp. That's not an issue for this swap.

[Ondonti]

i would say 600-700hp cast crank, 850-900 forged. At those power levels, you crankshaft will start to crack and eventually fail over a few years so it will need checking and replacement. Most of us dont have to worry though.

[phantomrt]

Did anyone ever figure out why the TT 6G72's like to wipe out their two center main bearings? Ray Pampena says it is detonation that causes it, but that doesn't make sense that detonation never occurs on the other cylinders and wipe out the two outside mains. Forged or cast cranks, it still seems to be an issue.

From DOHC to SOHC, there are VERY few similarities. The similarities are the bell housing bolt pattern, crankshaft, connecting rods, rear main seal and rear main seal retainer, I think the water pump HOUSING is the same, but the pumps are different because of their pulleys. I think there is one other thing I am missing, but literally EVERYTHING else is different, including the blocks. DOHC engines, including the TT's also have cast iron crankshafts up until a certain year like 1993 or 1994.

[Ondonti]

Its because the center two pistons have the least amount of main bearing devoted to supporting them. Pistons 1 and 6 have a main bearing almost solely devoted to them while then center 4 pistons share the center 2 main bearings.


Also, switching to a stock heavly flywheel and using a stock crank pully on your dohc motor is a good idea, or adapting a sohc harmonic dampner to a dohc motor (dohcs dont have a real one so they have a special crank pulley).