This a really, really weird deal for me. I've been running my 440 Source heads on my 440 for about a year now. I clearly remember when I got the heads and put them on that I didn't have spark plugs at the time. So I went to the 440 Source website, and yep, they stated you have to run "Their spark plugs".
On the 440 Source website they don't tell you the make or size spark plugs, just the order number:
So in my mind at the time, I knew the deal, 440 Source doesn't make their own spark plugs, they just stock over the counter plugs that fit their heads and make you order thru them at an inflated price.
So here is where my weirdness starts I guess: I get the 440 Source ordered plugs in the mail, and they are in an 8 pack (8 single packs in a loose box), put the plugs in back when, and this weekend it was time to change them all out for a tune up
I pulled all 8 out. Six are Champion RC12YC Two are Champion RFN14LY: These two have electrodes that are a full 1/2 longer than the other six.
And I haven't changed any plugs out since I installed the original 8. I am thinking maybe the pack was packaged with two wrong ones, who knows
(I dont have any other vehicles that run a small head, 5/8" type spark plug)
And the car has been running fine, plugs show no issues
So now I have to ask: What ARE The proper plugs to be running with 440 Source RB heads?