Ngk Spark Plug Gaps

[pamitchell]

What plug gaps are folks setting for NGK plugs w/ 91 octane fuel?

[gjz30075]

Mine's set at .030, using a Lucas Sport coil, BP5ES plugs

[type26owner]

I'd use the manual's recommended .020" gap if they were still available. Close as one can get these days is .025" so that has to do.

For commuting I use 87 octane cheap stuff and just backoff the total timing about an extra two degrees. It runs sweet.

If you want to really want improve the flame pattern in a hemisperical head it's long been known that clocking the spark plug so the ground tang is not shadowing the flame path towards the center of the piston and not splitting apart the flame boundary is a little beneficial. IIRC, it's only a few percent improvement though. However, it's definitely the thing to do for a race engine to extract the maxmum performance.

I've been trying the really cheap resistive copper core Autolite plugs lately. The 63 is not hot enough to self-clean. The 64 is too hot. Damn it all anyways! Back to those rather expensive NGK ones again that have smaller thermal increments to select from.

[mikefromengland]

are they emission or non emmision.20-25 thou is right unless your using electronic ignition then you need a bigger gap 30 thou+ to cater for the greater spark.regards mike