This is the official V8 fork of Node.js with a recent V8 version.
To build from source, run
git clone https://github.com/v8/node v8-node
cd v8-node
./configure --build-v8-with-gn
make -j4 nodeOr download the latest build for Ubuntu from this build bot. Select a build, then use Archive link download.
To check the V8 version in Node, have a look at v8-version.h or run
node -e "console.log(process.versions.v8)"