There seem to be a lot of threads this year from newb Z owners (or would-be owners) who want to purchase high-mileage Zs and replace the engine with rebuilt units. Even if you're just replacing a NA VQ and not upgrading to a FI custom job, there are a host of factors to consider. Here are a few of them to be stated up front:

1) Getting a rebuilt engine is not a guarantee of trouble-free driving. Ancillary parts that are critical to the engine's performance are NOT INCLUDED in a rebuilt motor. Parts like the alternator, intake plenum, exhaust, starter, various sensors and so on have been taken off the car and must be reused.

2) Depending on whether you buy a full engine or a shortblock, you may also need to reuse the left and right heads of your old engine; together with the overhead cams and ancillary parts of the top end of the engine.

3) The time to get a full mechanical assessment of your car is BEFORE you buy it. Make sure you ask for compression and leakdown tests to be done to determine what condition the engine is in. Any trouble codes (CELs) should be analyzed and disclosed.

4) The Nissan VQ engine is a true world class V6 and has won several awards for it's design and performance. The precision alloy block is matched with close tolerance internal components to produce smooth power and torque. With good quality oil/filters and regular changes, it should deliver excellent performance performance for hundreds of thousands of miles. But let it overheat, hack the wiring harness or worse yet, flood the engine or electronics, and you can destroy it.

5) Replacing the VQ is not an impossible task, but HOW it's put back together is critical. A rebuilt modern engine needs time and patience to be installed properly and for all the electronics to function properly. Don't assume you and your buddy can do it over a weekend if you lack the tools, experience or gumption to get it done. And if you're paying someone, it's not a $100 job...