ChrisLex87

I wanted to know could you drop a ls430/gs430 motor in a gs400 without modification???

GZS160

Yes, but there are of course a few differences between the 3UZ and the 1UZ. Mainly the wiring; for instance the 400 uses the early drive by wire with the cable and pedal sensor where as the 430 uses the later system without the cable with the sensor on the pedal. But physical the engines should swap easily. Personally the work doesn't justify the gains, why not just buy a 430.

ChrisLex87

I was asking because I might need a new motor and thought which one would be best

akafixture

Stick with the 400, drop it in and drive. The differences are minute.

Tank

iTrader: (19)

You will need ALL of the 3UZ's wiring, (engine management etc). electrical will be your biggest challenge.
Why not stick with the 1UZ and add some aftermarket power to compensate for the missing 0.3 liters?

JLAWS

I believe it would be easier to put a 3.0 I6 Supra engine in it that the 4.3 V8.

Stick with the 4.0 in the GS400 or just buy a GS430

RamAirRckt

Can't you simply drop the GS400 throttle body on and call it done? Isn't the rest the same?

Now, be VERY aware, the cams are different in the GS430 than the GS400, and the timing curve will not be ideal, and it could cause drivability issues that can't be solved.

Now, if you drop in the 4.3L engine and the 4.0L Cams, that would be a better choice. The ECU will be off with the displacement change, but it ~should~ be in the realm of being able to handle it.

Displacement change will only affect AFR, which is already screwed up thanks to our politicians who play chemist and mandate we run E10 fuel (aka, 10% ethanol) which Lexus NEVER designed it to run. It CAN handle 10%, but it was TUNED in Japan for 100% gas, not 90% gas/10% ethanol.

Think of it this way. 4.3L as is, computer will have timing maps messed up (peak torque on a GS430 is significantly different than the GS400), the cams will dictate that. Displacement change on the ECU will only affect AFR.

If you need to use a 4.3L, fine, use the 4.0L cams and 4.0L Throttle body and if you have to, intake and GS400 wiring harness and ECU. That would be less invasive. Can't say it will be 100% check engine light free, but likely it will handle it better.

NVR2EARLEY

AS LEXTREME AND PARTY HAVE STATED:

Thanks to you I have studied this and like documents previously.
Notice in addition to the changes listed that the 1UZ piston has more material in the piston deck, edges and around the pin boss. I am surprised that the ring pack is tighter on the 1UZ vs. the 3UZ as that area looks beefier on the 1UZ. Also the piston pin hole location looks to be farther from the deck on the 1 vs the 3 assuming these are correct scale engineering drawings.

Another interesting observation is the change in camshaft VVTi timing between the 1 and 3. Earliest opening and closing of the intake valve is 5 degrees less in the 3. All else would indicate identical camshafts. Cam lift would be nice to have factory documented. Reports from the field indicate just over .300” lift on the pre VVTi engines and .350” on the 1998 and later VVTi engines.

All else equal a bigger bore creates higher compression and since the 3UZ has the same compression ratio as the 1UZ but the 3 has a smaller combustion chamber the net dish volume in the 3 must have enlarged although not apparent in the pictures. Certainly some of this would have come from the elimination of the thrust squish/qwench areas.

A clear error on the drawings can be seen in the dyno chart. It shows the 3 with more low end torque than the 1 but at the same time showing the 1 with more low end power than the 3. This is obviously impossible as is showing the 3 with more peak power even though they are both rated at 300hp. The torque curves look accurate but the power curves are skewed. This of course draws to question the rest of the image accuracy.
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ALL CREDIT GOES TO LEXTREME AND ASSOCIATES.

NVR2EARLEY

someone confirm this is the only issues?