What is the right weight oil for a new flathead engine?

[GeorgeColvin]

I would like to know what the right weight oil to use to break in a new flatehead 6?

[31Streetrod]

For your location and time of year the ideal break in oil would be 30W--non detergent.

[Corvanti]

For your location and time of year the ideal break in oil would be 30W--non detergent.

yep!!! 30 W non-det was the only oil ever used in my '40. no oil filter, so it was changed at every 1,500 miles or 3 months.