23rd series Custom Eight 356 spark plugs

Posted by 1508 On 2014/4/16 18:40:58

What are the correct spark plugs to use in a 23rd series Custom Eight Packard? Remember these are the larger 14mm plugs, not the 10mm ones used on earlier 356 engines. The ones I took out of the head I have are Champion model J11C. I have no idea if these are correct heat range or not.