Blueprint 427 Spark Plug Question

[cv2065]

Good Saturday to all! Have a question around spark plugs. The BP 427 that I have came with Champion C59YC racing spark plugs. Also designated as 792’s. Is this the best temp ranged plugs for a street car? From what I’ve read, they are on the cool side. Would Autolite 3924’s be more efficient?

[NAZ]

Trust what the engine builder recommends and adjust from there. You'll know soon enough if it's too cold. Starting colder is safer than inadvertently selecting too hot a plug. Unless someone has the exact same combo, same AFR, same timing curve, the same driving style and not too far from your operating altitude their recommendation may not fit your needs. Selecting the correct heat range on a new build is an iterative process -- there's no OEM manual that lists all the tested and true specs for your particular car and that's part of the fun.

As a rule of thumb, I start 1 heat ranger colder than OEM for every 100 HP increase in a N/A engine. At least 2 ranges colder if that extra HP is from a power adder. And I adjust as needed after reading the plugs.

[cv2065]

Thanks NAZ. I appreciate the input. I’ll run with these to start.