[jrhaelig]

Just be mindful of the other crud that may come loose.

I flushed the radiator on my '39 Buick with vinegar, then the soap from a dishwasher gel pack (they are all super-low sudsing).

Anyway - busted loose all kinds of crud in the block - that subsequently clogged my radiator!

The old stocking filter on the inlet pipe might have prevented the removal and professional cleaning that followed.

Good luck!