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Chris Haynes · 07-15-2017, 07:10 PM

I have read that when using an aluminum high compression head that it is advisable to retard the spark a few degrees. Why is this? Is this for aluminum only or does it also apply to cast iron?
I have a cast iron 5.5 head and I don't detect any pinging or pre-ignition by running timing in the stock position.

07-15-2017, 07:10 PM	#1
Chris Haynes Senior Member Join Date: May 2010 Location: Camarillo, CA and Pine Grove, CA Posts: 2,832	High compression head and timing? I have read that when using an aluminum high compression head that it is advisable to retard the spark a few degrees. Why is this? Is this for aluminum only or does it also apply to cast iron? I have a cast iron 5.5 head and I don't detect any pinging or pre-ignition by running timing in the stock position. __________________ 1921 Runabout 1930 Tudor Early 1930 AA Speed costs money. How fast do you want to go?