engine change. 4.3

[Lukasz00000]

I have a question if anyone has put the engine into a 2005 IS 250. 4.3 V8 engine. What problems may occur.  I was thinking about buying a 2005 gs 430.

[Linas.P]

I don't believe anyone did, or that it would be particularly easy thing to do, or that it is particularly good idea. 

Your best shot would be to get 2GR-FSE (from IS/GS350) because it would be direct fit without any modification (although A960E gearbox is too weak and you may consider A760E, so better get the engine together with gearbox). Why 2GR and not 3UZ - that is because 2GR has more power (slightly less torque), is much smaller, lighter and fuel efficient engine... and it is direct fit. Obviously you can somehow adapt gearbox to 3UZ, but only the adaptation of gearbox will cost more time and money than whole 2GR swap and this is before you approach elephant in the room - Lexus/Toyota ECU. They are not programable and there is no ECU that could run your combined 3UZ and A960E, alternatively you can use GS430 gearbox (A650E), but there are loads of problem with it - it is 5 speed, extremely outdated and lazy slushbox and it won't fit in IS transmission tunnel. So... you will need aftermarket ECU and high-end one for that to be able to run everything, and as well knowledge how to program it or money to pay for somebody to do that for you. I would guess only your ECU question will end-up being £3000 worth of "question".

Obviously the easiest swap and the one I was actually thinking to do my self (I have bot IS250 and GS300 for parts) was to swap 3GR into IS250, I understand this may not rock your boat as 40 extra HP is nothing to write back home about, but GS300 are plentiful and cheap, all parts are compatible and to be honest in my opinion 40hp is just about as much as IS250 needed to be enjoyable to drive (otherwise being just borderline slow). It gets much larger and heavier GS300 to 60 in 7.2s and same engine in US spec. IS300 does respectable 6.8s. Obviously both 3GR and 2GR swaps are not real "swaps", they are more of retrofits, because IS300 and IS350 were the models in Lexus line-up outside of UK, so there is no surprise everything is plug and play. Obviously, I understand that 3UZ swap is V8 and thus it is almost mini-IS-F and there is charm in that, but it is a lot of work and you are much better of simply getting IS-F or importing IS350 from Japan, by "better-off" I mean it would be significantly cheaper overall than making 3UZ swap to work. 

Other alternative - 1UR from GS/LS460, together with AA80E, they would fit in IS chassis... not quite the engine, for engine you would need custom mounts and modified subframe, but gearbox would fit... and that is not surprise - IS-F mule car was developed from the basis of 1UR prototype. GS460 are unicorns, but LS460s could be found. And the challenge of fitting 1UR is half of that of 3UZ + it is way more powerful, economical and modern engine and at that point you really only a hair behind IS-F. 

In summary - there is loads of problems which may occur and for most part 3UZ is simply not worth the amount of work required to fit it... hence it is not a popular swap (or that anyone has done as far as I know). 

[J Henderson]

Lexus themselves commissioned a "IS430" concept car to be built for SEMA in 2003.

IS430 Concept

1st-gen of course, and with a manual box, no less, but as Linas alluded to, the biggest challenge is the electronics.

 

[Mr Vlad]

Hi Lukasz. Great idea in theory but Far too much of a faff to do. It would be cheaper to sell your 250 and buy the F.

[Linas.P]

1 hour ago, Mr Vlad said:

Hi Lukasz. Great idea in theory but Far too much of a faff to do. It would be cheaper to sell your 250 and buy the F.

Probably magnitude of times as well and IS-F would still be way superior, reliable, purpose built car and have some sale value afterwards, whereas custom built IS430 would cost fortune to make and in case of selling - pretty much worthless. 

OP has not specified if he plans to use automatic or manual car for build, manual would have it's own set of pitfalls, but at least gearbox management would not be an issue. 

[Linas.P]

Here you go - https://www.copart.co.uk/lot/71931743/2014-lexus-ls-460-lux-sandy

Donor for 4.6L 1UR, quite a big shunt, but engine is unlikely to be damaged and it will go cheap as nobody needs LS parts, especially not 2014 ones. Lexus sold like 2 of them in UK (and one is sadly now gone)...