Here's a typical plug in my engine. It was starting to have a low speed intermittent miss that cleared up with RPM. These were NGK R5671A-9. I have no idea why I bought those. They look a little rich and probably a lot cold. I just bought a set of Champion RC12YC that Edelbrock recommends for their heads. What does anyone else run in an Edelbrock head and have good luck with? 9.5:1 compression, TA212 cam, headers, Q-Jet that might need to be leaned out.