Mike McGee wrote:

Continuation of topics from a tech Q&A session at Pineapple Racing in
Portland, Oregon on Feb 22nd.

Spark plugs are a topic that has crossed this list a couple of times.  The
points that follow assume that you have got your air/fuel mixture set
right.  This wasn't one of my questions at the tech session but the info
sure applies.

Heat ranges based on horse power usage:
(NGK heat ranges, lower # is hotter, higher # is colder)
Horse power     Heat range
up to 200       9
200 - 250       10
275 plus        11
If you aren't using NGK you'll need to translate the numbers above to your
plug.

When you pull your plugs to see how they are looking/burning, the threads
will give you a picture of how your heat range is dialed in.  The first two
or three threads near the tip will be discolored from the heat if your heat
range is right.  A plug too cold will show one or no threads discolored, a
plug too hot will have four or more threads discolored.  This of course a
general rule of thumb and your plug use will also depend on how you operate
your engine.

Mike McGee, RV-4 N996RV, O320-E2G, Hillsboro, OR
13B in gestation mode

 
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