I have been thinking about this and just starting to do a little research but not getting real far. Alot of other cars like Acura, Nissian, and other can do this for a ez inexpencive hp gain of 20hp or more gain. This would only apply to the 1uzfe 4.0 VVTI motors but.... here it goes.

It's possible that the intake mani, throttle body, and or Cams may be different on the 3uzfe 430 motor. In some other engines because they are so close, it's sometimes possible to relpace the intake manifold, and throttle body and see a gain if they are different. Also the cams may be a direct swap drop in, and may possible have a little more lift and duration. The honda guys can drop in the 3.2 Type S Acura cams in the 3.0 Honda motor and get about a 20 hp gain or more with intake and exhaust gains. Anyone know or have access to the specs ?

1. Is the throttle body the same mm opening ?

2. Is the VVTI intake Mani the same, not just bolt on compatiable but same size ports ?

3. What are the cams specs ? ( Lift & duration ) 4.0 VVTI Vs 4.3 VVTI.

Its worth a look

 

I unno, man... I'm not the expert here, but the 430 motor only makes like 10 more hp and like 15 more lb-ft of torque, I think. And that's at the crank. I wouldn't do more than swap throttle bodies for that.

 

you would be better off with a port match and polish. If this was a viable option i think we would have seen people doing it by this point. As mentioned, the differences from the 1uz to 3uz aren't huge save for displacement, compared to say the honda 3.2 which produces about 250hp vs. the 3.0 which produces just about 200.

 

I think the best answer would be for someone who can get it to post the specs.

1) 4.0 VVTI vs 4.3 VVTI cam specs. Lift & duration of both.

2) " " Throttle body opening size of both.
I think the 4.0 VVTI throttle body opening is 70 mm.

3) Are the intake Mani ports the same size ?

I think you guys are kinda missing a point. Larger throttle bodies do increase hp most times.
Mildly Higher lift and duration cams do increase hp most times.

 

I don't think the cams are different and doubt the throttle body is. You could have a machinist enlarge the throttle body but make sure there is a need. Same goes for the intake. The 430 is listed as the same peak HP as the 400 but at a lower RPM (300 @ 6000 for 400 vs 300 @ 5600 for 430)

Below I will relist numbers I posted back in 1/05

 

Details

https://www.clublexus.com/forums/per...s-gs400-2.html

The factory listing that I have is slightly different at:
230 degrees intake duration (-14 ~36 BTDC, 64 ~14 ABDC)
229 degrees exhaust duration (41 BBDC, 3 ATDC)

 

ok, thats the spec on the 4.0 VVTI.

I had this info on the Valve timming and it is different on the 4.3 VVTI, but I can't find the 4.3 Cam lift and duration specs.
http://www.lextreme.com/forums/3uzfe.pdf
Look at the 430 Valve timming on page 2, it's different, unless they're measuring at a different point.

From what I've heard the intake cam and Intake ports are not that bad and ez to improve, but it's the Exhaust side that does not flow as well and shows some gains with improvements with changes.

If that Exhaust cam on the 4.3 is a little bigger and has a little more lift, it would add some hp on the 4.0 motor, and be very interesting, especially with Headers and exhaust.

 

Recheck the Lextreme link. The exhaust timing is identical. The intake is as well except that it is advanced 5 degrees which aids the low end. Lift is not listed but you would think it would be mentioned if it were.

The other significant changes (to this discussion) are the valve angles getting tighter and the intake using longer runners. That intake should pick up low end on a 4.0 engine. Heads may be potentially better due to valve angle but have larger bore design which may not work properly with quench and valve shrowding.

I would measure intake vacuum at peak power to determine if a larger throttle body has power potential. I for one would like to bypass the throttle by wire for better throttle response under some conditions.