With an Offenhauser intake, I used water from the cooling system. With a Fenton intake, I am using copper tubing from the exhaust manifold to a plate on the intake manifold (Jim Carter sells a kit).

https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=459640#Post459640

https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=421608#Post421608