Engine swap advice

The Nissan will not fit without major work and a lot of changes to the engine itself. The engine sets the wrong direction, entirely different fuel system, exhaust, cooling, you would need new wiring and custom programmed control systems as a start.

The Buick 3.8 will not work very well either because you would need to rewire the engine bay, change out the fuel system and custom make a new exhaust. The engine controller would need to be reprogrammed as well because of the changes. And it would need the older transmission because the current 3.8 you have is a different design than the earlier engine.

In reality the only thing shared between those engines is the 3.8 number. If you really are looking for more power you would be better off finding a bird with the V8 in it from the factory, those have a lot of performance parts available.

USER NOTES The info about the Nissan engine sitting a different direction is incorrect the GTR is AWD and the 380Z is RWD in which both cars have the VR38 3.8 Nissan engine

You can't simply "drop" a V8 into a 6 cylinder car.
You have an operating system for one engine and one engine only. The suspension is different, the cooling system is different, the exhaust system is different, the brakes are different, etc, etc, etc

Not to mention that it's totally against federal law to do that punishable by up to $25,000 fine.

Check to see if it 's the correct flywheel there are a cople different ones. If it's an automatic the converter may have slipped forward and that is your problem. If it didi dont' be surprised if it broke your oil pump in transmission either.

The best way is to do it like it's supposed to. You drop the engine and trans and cradle assy then take the trans off. If you r conveter has slipped your pump my have broken so you'll have to check that. The convertershold be sl;id back after trans is out or loose it has to go into pump otherwise it breaks it. It will slide forward a little whe it is bolted to the flywheel.

As long as the torque converter never came out then you are ok.

Don't worry about it

Not being able to see this i'd really suggest you have a local pro look at this for you. I don't know what to tell you.

We recommend direct replacement parts. This type of change can be done, but requires that everything be changed, such as motor mounts, trans, computer, vacuum hoses, wiring harness.

And, after everything is changed, there always seems to be additional problems. That us why we only recommend direct replacement parts.

There will be a few things (flexplate, starter, harmonic balancer, possibly p/s exhaust manifold). Not really sure if it is worth all the extra stuff you have to buy to put the 350 in it, done it before, not a really huge performance increase. PCM calibration will also be off a little, injectors may be different, dont remember on that.