----- Original Message -----

From: John Slade

To: Rotary motors in aircraft

Sent: Tuesday, March 25, 2003 5:37 PM

Subject: [FlyRotary] Re: Spark Plugs

>Tracy, there are a few  "Standard" spark plugs which while their base is 3/4" long, their electrodes will not 

>clip/chip the apex seal.  However, that is by no means true of many/most "Standard" spark plugs. 

 

OK. Now you guys have me worried. I got a recommendation from somewhere to use B9EGV and B10EGV plugs. I forget who told me this, but I'm pretty sure it was someone flying a 13B. Are these plugs ok? Will they burn up? will they hit the apex seals?

John Slade

Ready to start her up & fly.... once I have an intake system.

 

John,

 

You are ok with the B9/10EGV plugs in so far as clearing the apex seal.  The E in the designation stands for a 3/4" screw portion.  There are, of course, many a plug with the "E" which are 3/4" long same as the B9/!0 EGV, however, apparently there is no standard about how far an electrode may reach beyond the base and that is what causes the problems with clipping the apex seal.  Paul Yaw had nice tech article on spark plugs in which he points out this problem.  In some cases, he actually modified the electrodes (i.e. flattening them close to the base of the plug) to prevent them from clipping the apex seal.

 

So, again, you are OK with B9/10EGV plugs and their are others that may also work.  Just be careful.

 

Ed Anderson