Running hotter plugs

[RafM]

1972 Twin cam

Since finishing my restoration I've been having trouble getting the engine to run cleanly, even after careful tuning and carb adjustments (twin dellorto)

Having read through some older posts I decided to try a hotter plug, the difference is huge. Easier starting, clean idling, no misfiring and much more
responsive from lower revs.

Great information that I would not have thought to try.

[BDA]

I'm assuming you have a twink motor. Which plugs are you running?

[RafM]

Yes, TC I mentioned it on top of the post   

NGK BP6ES

[Clifton]

It's not your plug temp.  If your plug was way too cold it could foul but if it's a stock plug it just isn't going to. Richard Holdener has a video on Youtube dynoing plug gap and heat ranges surprising little difference.


Vac leak, ignition timing, or AFR. Did the distributor get touched? Do you have a wideband and timing light?

[BDA]

Yes, TC I mentioned it on top of the post   

NGK BP6ES

Sorry I missed that you said you had a TC!

NGK 6 heat range is the heat range that is most appropriate for a TC.

Clifton is correct that the heat range impacts fouling more than anything - especially for street driving. A plug that is too hot could cause preignition or detonation but that is more likely in a high performance situation (obviously, timing is important too).

There is an issue where heat range can impact is drivability. I don't know if this is potentially a problem with Strombergs but it happened to me with my Webers and I suspect dellortos would react similarly. When I was running NGK 7 plugs, the car ran well but one time I made a hard stop at a stop light and the engine almost died. Someone much smarter than I told me that the hard stop sloshed extra fuel into the combustion chamber and fouled the plug. Going to an NGK 6 heat range plug cured the problem.