REFLECTOR: Spark Plug Gap

Tue May 12 11:03:15 CDT 2009

Appreciative thanks to everyone for the good info on the spark gap and automotive plug alternates.  Traditionally trained technicians are always agape at the size of the gap when they are used to looking at the mag gaps...it takes a bit of convincing.

Ken Mishler stopped by this last weekend for some 'consulting' on N27GV....the visit was most opportune as I discovered a fuel leak from the pilot side tank that was coming out in the wheel well area near the base of the main gear on the XLRG and proximate to the fuel outlet line from the pilot side tank.  With judicious grinding and digging, (with big fire extinguisher very near by),  Ken exposed the 3/8" fuel line and where it penetrated that tank.  It was obvious the fuel was coming from that general area.

With good prep clean up, Jeffco was applied to the area while I pulled a vacuum on the tank with the shop vac.  Ken believed he saw a small amount 'pulled into the area of the leak, but the volume is so small, it's difficult to say with certainly.  With that part of the procedure done, Ken mixed the remaining Jeffco with micro and the ground out area was filled with the Jeffco paste.

The next, we added fuel and whalla; no leak.  With addition of a layer of fiberglass to dress it out, it was good-as-new, or perhaps a tad better.  Visions of disaster turned into a non-event.  While here, Ken and I worked with the mechanical nose gear door closing mechanism (okay, Ken worked and I watched), which has been very successful and more reliable than the original hydraulic system, to simplify installation instructions so there is more science and less art (nice word for 'guessing') in its correct positioning for the desired results.

So again, thanks for the input and it's good to be back in the air.

Chuck Jensen 

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]On Behalf Of Kent Murley
Sent: Friday, May 08, 2009 12:05 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Spark Plug Gap

Chuck - 

Thanks for info you have provided over the years. Finally I have a partial answer for you.

I also have an IO540 with Jeff Rose ignition (on the bottom plugs).

At

http://www.electroair.net/

it recommends .030 - .035 inch gaps for the aviation plugs with thick electrodes like the REM37BY. I've had good luck with that gap.

Brand? I've used Champion and Unison (Autolite) and have not found a difference. That's Elbonian for "both brands are as easily dropped on the floor as the other by well-meaning mechanics".

Don't have any experience with auto plugs but Jeff and his protege have a caveat on their FAQ page about the heat range. 

For my top plugs with a normal gap I've had to fork out for Iridium plugs to prevent fouling but that's probably because of my improper leaning technique on the ground, the humid air near my hangar, and my infrequent flying.

The extra $50 per plug for iridium plugs seems worth it now compared to the down time taking my cowling on and off some 5 or 6 times, but more importantly, having to do that in front of waiting passengers a couple times.

Kent Murley
Tacoma WA

On May 8, 2009, at 7:59 AM, Chuck Jensen wrote:

Quick question - what is the recommended spark plug gap for Rose Ignition with Avionics plugs?  Or auto plugs, recommended brands?
Engine is IO540.  Thanks.

Thanks, 
Chuck Jensen
Diversified Technologies 
2680 Westcott Blvd 
Knoxville, TN  37931 
Phn:    865-539-9000 x100 
Cell:    865-406-9001 
Fax:     865-539-9001 
cjensen at dts9000.com

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.tvbf.org/mailman/private/reflector/attachments/20090512/ba373e0c/attachment.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/jpeg
Size: 1820 bytes
Desc: rocketsurgeon.jpeg
URL: <http://www.tvbf.org/mailman/private/reflector/attachments/20090512/ba373e0c/attachment.jpeg>