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06-15-2014, 11:28 PM
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Join Date: Mar 2008
Location: Seattle
Posts: 1,412
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Bob;
Thanks for the pic. Could you fill us in on the engine details, so we can objectively compare that spark plug?
What is your engine's displacement, compression ratio, and what cylinder head temp do you usually run? Do you tend to run near full power (I do  ) or idle around to save gas?
These would be the most important factors I can think of.
If you have 8.5:1 and run cylinder temps of 380F, a 7:1 engine that runs 320F Cylinder temps might be fine with the plug you show.
I am trying Autolite 386 plugs (on a P-mag), as Smokeyray had been using. That's an 18mm resistor plug. I have an O-290 with 7:1 compression and run cylinder temps of 320F most of the time (in my T-18). Perhaps any O-320, O-360 or O-540 with 7:1 pistons could use these 'hotter' Denso L14-U or Autolite 386 plugs.
The higher compression engines would need a colder plug than the one you show, and that's tough to find in an automotive 18mm resistor plug. These might require the cooler NGK BRE8ES, or other 14mm plugs and the adapters.
__________________
Scott Emery
http://gallery.eaa326.org/v/members/semery/
EAA 668340, chapter 326 & IAC chapter 67
RV-8 N89SE first flight 12/26/2013
Yak55M, and the wife has an RV-4
There is nothing-absolute nothing-half so much worth doing as simply messing around with Aeroplanes
(with apologies to Ratty)
2019
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06-16-2014, 06:57 AM
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Join Date: Jun 2006
Location: 8I3
Posts: 3,564
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Stock O-360. They're still doing ok.
Years ago I ran the Autolite 386's in my stock 360 and found the electrodes would start rounding off. Not seeing that with L14's.
I have had very good luck with BR9ES/adapters.
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Please don't PM me! Email only!
Bob Japundza CFI A&PIA
N9187P PA-24-260B Comanche, flying
N678X F1 Rocket, under const.
N244BJ RV-6 "victim of SNF tornado" 1200+ hrs, rebuilding
N8155F C150 flying
N7925P PA-24-250 Comanche, restoring
Not a thing I own is stock.
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06-16-2014, 09:39 AM
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Join Date: May 2014
Location: Savannah
Posts: 806
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The PMag adaptors are crack/failure prone. Check out the naval brass adaptors EFII sells. I have not tried these brass adaptors yet, but I will be installing some on an airplane I maintain.
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06-16-2014, 09:53 AM
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Join Date: Oct 2011
Location: Atlanta
Posts: 878
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Quote:
Originally Posted by Mike H
The PMag adaptors are crack/failure prone. Check out the naval brass adaptors EFII sells. I have not tried these brass adaptors yet, but I will be installing some on an airplane I maintain.
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As far as adapters go, they are the bees knees.
__________________
RV-8 IO-360 (Bought)
RV-6 O-360 C/S (Sold)
Walkman aka Flame Out
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06-16-2014, 12:14 PM
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Join Date: Jun 2006
Location: 8I3
Posts: 3,564
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More specifically the adapters that are machined out of aluminum bronze are better.
__________________
Please don't PM me! Email only!
Bob Japundza CFI A&PIA
N9187P PA-24-260B Comanche, flying
N678X F1 Rocket, under const.
N244BJ RV-6 "victim of SNF tornado" 1200+ hrs, rebuilding
N8155F C150 flying
N7925P PA-24-250 Comanche, restoring
Not a thing I own is stock.
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06-16-2014, 03:17 PM
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Join Date: Jan 2008
Location: Upland, CA
Posts: 286
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bronze vs brass
Aluminum bronze is a more brittle alloy. Naval brass has more malleability - better toughness.
We make our adapters in house on our Conquest 42 lathe. That's why we can afford to make them the best they can be  In fact, we make all our mechanical parts in house. This is invaluable in achieving high quality, rapid product design and evolution, and providing the best parts possible.
In fact, we're running some spark plug adapters right now (pic below)
Robert

Last edited by rcpaisley : 06-16-2014 at 03:34 PM.
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07-28-2014, 01:26 PM
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Join Date: Jan 2005
Location: Sedona Arizona
Posts: 349
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Quote:
Originally Posted by digidocs
Bob,
Are those plugs really as hot as this chart would seem to imply?
Thanks,
David
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I did not see a reply on this important question regarding heat range of the various auto plug options that eliminate the adapters. From the chart above it appears that the Denso 14s are several steps hotter than the NGKk 8s.
Regardless of the successful use of the adapters by a number of people, I really do not want to add an extra set of threads into my combustion chambers.
I have researched heat ranges of the various plugs but have had a hard time finding a comparison of the auto plugs with the aviation variety.
Are the Autolite 386 plugs the same basic heat range as the Denso L-14U? And are they both essentially the same heat range as the NGK BR8ES plugs?
Randall, about to order Pmags...
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07-12-2015, 04:09 PM
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Join Date: Apr 2015
Location: Sunny Florida
Posts: 26
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Sit rep
Guys,
It's been a little while, how have the auto plugs been holding up ?
Any issues with these plugs fouling due to avgas ?
__________________
Save Money - Outsource Congress !!!
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07-13-2015, 06:15 AM
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Join Date: Jan 2005
Location: Yorkshire, England
Posts: 2,052
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150 hours on a split install.
2 P-Mags with Tempest on bottom and NGK BR9-EIX Iridium (part No 3981) - CHT's ran a little high, but all was well.
Plugs installed as per Brad's instructions with no problems.
After 150 hours, we changed a few things.
New lower harness, swapped the airplane plugs for more NGK's, re timed the motor and had a good seal around the plenum. I know, we changed more than one thing, however, the CHT's came down by 50f !
We now have around 300 hours on the motor
TMX IO-360, 2 P-Mags, MT 3 blade c/s prop.
All well, temps great, plugs show no fouling on avgas, we get them either at O'Reilly's or Amazon for around $6 each. Swap them twice a year.
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"I add a little excitement, a little spice to your lives, and all you do is complain!" - Q
Donated in 2020
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07-13-2015, 08:39 AM
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Join Date: Jan 2005
Location: Houston, TX
Posts: 868
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Quote:
Originally Posted by Ghost two-six
.... how have the auto plugs been holding up ?
Any issues with these plugs fouling due to avgas ?
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I've been running dual Pmags with NGK BR8ES plugs on my RV-8 since day one; currently at 1150 hours and have had zero problems with the plugs. I run a mix of mogas (maybe 25%) in with 100LL, but have never had a fouled plug. I usually run a set of plugs for some 150-ish hours before replacement, which sets me back a whopping 2-3 bucks each at Autozone... nice.
__________________
John Bixby
RV-8 QB sn 82030 - 1750 hrs
O-360-A1D/CS/Pmags
Houston, TX
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