Alternatives to Gen 4 Engine Swap

You'll definitely want to talk to this dude in Oklahoma: http://www.skimmilkhybrid.com who did a massive number of Gen4 into Gen3 Prius. He's been thinking what you've been thinking for a while because the quality of used Gen4 engine has gone down. So he decided instead to switch to a full rebuild of Gen3 engines to make them more powerful and more reliable. But then maybe he got more orders than he was interested in doing because I tried to get a couple engines done by him and he always wanted to talk about other stuff.

It sure would be nice if this discussion found a solution that was better than what's been done before.

 

What's the miles and has the EGR system (including intake manifold) been cleaned?

Ah never mind, you're just contemplating a purchase. If you're set on a third gen purchase, I'd try to find one with under 100k miles, be prepared to clean the full EGR system thoroughly. You'll see a lot for sale with over 150k, and odds are about even it's being ditched, with a stop-leak product temporarily holding the head gasket.

 

A gen5 engine is completely different with 2 liters, dual port and direct injection, different variable valve timing - the list goes on.

You have to have an almost identical 1.8L engine to have a chance for gen3s elaborate computer systems to work. Even gen4 swaps end up being frankengines with parts of a gen3 bolted on to make things fit.

So - many have realized the best solution is a rebuilt engine - something dealers and pro shops have known all along.

A big part of that is eliminating oil burning - which requires revised pistons and rings, along with improved ecm software, egr valve, intake manifold and head gasket.

You then hope the $2k cat is not 95% clogged from the oil burning.

Prevention is water under the bridge unless Mendel will sell you his garage queen. Luck is fickle but maybe you will get one of the thousands already updated by Toyota when they did it for free. But clean Gen3s previously updated and not burning oil are unicorns and not often sold for the affordable prices you see on FB Marketplace.

A low cost "head gasket" fix is a gen3 JDM engine swap. Its lady luck at play again - you win big if the $1k engine is from a 2017-21 Japanese Prius v/+/alpha with all the updates. However there are no US vins to verify year and an inspection at a local JDM engine distributor can only show so much.

A gen4 engine is best packaged in a gen4 car. The car could be a Prius, Camry or Rav4. Any used car needs a pro assessment before purchase.

 

The only people who have tired to install the Gen 4 engine in the G3 that have been successful are the ones
That have used the Gen3 head.
Too many modifications, and messing with sensors.
But if you get the updated block, you shouldn't have the issues.