Here is the before and after since the switch to summer gas and no more octane boost. I still need the right plugs for my elderbrock heads I have but still not sure which ones to buy. I just know they need to be flat and have washers. Anyone have a part number for the plugs I need? Anyways car seems to be running richer


Previous spark plugs both sides of the motor look the same so I didn't picture all 8 of them
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NGK hot to cold;

FR4
FR5
6962
4644
These are a 3/4 reach, gasketed with a 5/8 hex.