Getting ready to fire up the 512 stroker and need some in put on what length plugs and what number and what brand . Has Eddy performer alum heads and is 11/1comp with 509 purple cam and M1 intake with 950cfm proform with msd ign and tti headers .Roller cam will come when $$$$ alow.what kind of power should I make??Its a four speed car.with 4:10gears @3800lbs..these heads are angle plug and have a deep thread for the plugs..I tried a j12y and it only went in 1/3 of the way..plugs would be fireing inside about 1/2 inch inside the threads...HUH ????

Edelbrock recommends Champion RC12YC with those heads.

Mancini's site has plug recommendations by compression ratio for aluminum heads. I've done fine running their recommended NKG's. There are recommended Champion's also.

What you need is a small block style plug. 3/4 reach w/ a 5/8's hex nut. I made the mistake of reusing my big block iron head plugs when I switched to the Eddy heads and let me tell you, It wasn't pretty

I run an Autolite Ar 3924

RN9YC in Champion #12 heat range too hot for 11-1 comp engine.

Use the plugs that Edelbrock recommends in the instructions.

Andy F ..the car owner called Eddy and spoke to.Mr Stinson...Like the head honcho and he said rj12y plugs ...but they don't fit...I will try to call him Monday and explain what I see..It for sure needs long reach small block type plugs..Thanks

Why call, just read the instructions.

I'm runnin that 512 kit with a 6pk set up & use RC9YC4's. The ones Edelbrock recommends are toooooo hot like was said earlier in this thread.