Re: Correct spark plug for 1924 Model D Elto Ruddertwin Home › Forum › Ask A Member › Correct spark plug for 1924 Model D Elto Ruddertwin › Re: Correct spark plug for 1924 Model D Elto Ruddertwin The Boat HouseReplies: 4550Topics: 111 April 3, 2018 at 3:17 pm #73405 I’ve never had good luck with Champion’s including the D-16. I use the AC C-87 in my Super Eltos if you would like to have another option.