That happened to me. I finished rebuilding the engine, put it in the car and started it up. Got the classic wooph and saw flames.
The only fire extinguisher I had on hand was a ABC dry chemical.
What a mess! That stuff was "ALL" over the garage.
I pulled the engine (little if any damage) and washed it down with a solution of baking soda and water. Good as new and that was 15 years ago. As long as the engine is off nothing will be ingested thru the carbs and your engine will be fine.
Fred
