[Aussie Mike]

Early ls1 motors had a steam pipe cross over front and rear of the motor. These were then connected together with a pipe running under the manifold. With the introduction of the LS6 the rear cross over and tube under the manifold was deleted. I think this was mainly because the plenum area of the LS6 manifold is deeper and it sits down closer to the valley plate so no room for the pipe.

I've seen where people have drilled out the steam pipe holes and used AN fittings. I'm tempted to do this myself. I have just silver soldered some Bundy tube into the original bosses and soldered on an AN-6 fitting in the middle. I made up a matching cross over at the rear that eliminated the front to rear connection.

The header tank had an AN-10 on the bottom that ran to a fitting about half way up the radiator tank. 2x AN-6 fittings at the top were for purge. One ran to the steam pipe on the motor and the other went to a -6 fitting on the top of the radiator tank. The system filled really easily with air being purged from the motor and the radiator at the same time.

The tank is on Gav's car now.

Cheers