Manual Spark Advance & Kick-back

[Ian Curtis]

Alrighty,

I did not pay enough attention in combustion in college, and I am hoping someone who did might be able to clue me in.

I have an old truck (see profile picture) with a manual spark advance. For those following along at home, this means you the driver control when the spark plug makes a spark, which ignites the fuel in the cylinder. For maximum power, you actually want the spark to fire before the piston reaches top dead center as it takes a finite amount of time for the mixture in the cylinder to combust. However, if you were to start the car with the spark firing before top dead center (TDC), there is a chance that the engine would spin backwards and break your starter (or your arm if you were hand cranking it). For this reason, you start the car with the spark retarded which means that spark happens after TDC which should guarantee the engine spins the right way.

I was always taught to retard the spark when starting old vehicles, and always have. But...

I recently purchased a copy of the Service Bulletins from the late 20s/early 30s, and in them Ford recommends starting a warm car with the spark advanced. Is there something about a warm block that speeds up combustion, or did Ford just have some extra starters they needed to sell?