Thread: What spark plugs to use

I only get a small blip of knock when letting off or or shifting at WOT. Recently I have been getting some knock under light throttle, with a load on the engine between 1k-2k rpm.

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Buy 606 coppers, 0.60" gap. If she's happy, swap to 606 iridiums so you don't have to keep changing spark plugs (or don't if you like the chore).
If she's not happy, try 605 coppers. If she's still not happy, then you broke something.

Originally Posted by charlie31603

I only get a small blip of knock when letting off or or shifting at WOT. Recently I have been getting some knock under light throttle, with a load on the engine between 1k-2k rpm.

You didn't tell us what your current spark plugs are, so they could be the issue. Old version ZZP wires make knock, and I'll bet your tune isn't as dialed-in as you think it is.