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Spark Plugs on P-Mags

Bob Brown

Bob Brown

Well Known Member
I'm beginning my first condition inspection and wonder what experiences those who are using P-Mags/E-Mags are having with spark plugs? Any preferences or bad experiences? The plugs shipped with my system are NGK BR8ES. I've got 80 hrs on them, they all look OK but I was just wondering what anyone else is running??
 
Not much different to report here; I'm using the same NGKs with my P-mags and all is well with 'em at 140 hours. I might change to a new set around the 180-200 hr mark, we'll see...
 
spark plugs

yes they may look fine but I bought 8 plugs today for $12.50. So why not change them out at each annual?

Tom Lewis
RV7a - two PMAGs
 
Working great

I use the same plugs. I replaced them at the Condition Inspection with 180 hours on them. At a $1.78 each why not. At 100 hours I removed the plugs and cleaned them. All of them looked great with no bad signs at all.

I'll probably pull my plugs and clean them before saddling up for Oshkosh. I'll have around 100 on the new ones by then.
 
Rumor has it...

One of my neighbors, an early adopter of electronic ignitions on his -4 and now his -8 uses a spark plug he buys at tractor supply houses...it's the same thread size as the aviation plugs but is an auto style plug. He swears by em...I'll post the specific info when I get it on Saturday and will probably try a set if for nothing else to eliminate the brass thread adapters...which I really don't like using.
 
To clarify, I'm using the BR8EIX Iridium plugs, which have a fine tip and are supposed to have a better spark. I have no idea if that's true or not, but since they cost a bit more than standard, thought I'd leave em in for a while. Will probably go with the BR8ES next annual and see if any change is noticed.
 
Bob Brown said:
One of my neighbors, an early adopter of electronic ignitions on his -4 and now his -8 uses a spark plug he buys at tractor supply houses...it's the same thread size as the aviation plugs but is an auto style plug. He swears by em...I'll post the specific info when I get it on Saturday and will probably try a set if for nothing else to eliminate the brass thread adapters...which I really don't like using.
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I'd guess he uses the Autolite 386. It would be sorta nice to get rid of the adapters, but I gotta be honest...if it ain't broke, don't fix it. That's why I'm stickin with adapters + NGK BR8ES. Cheap & reliable.

I swap my plugs out every 100 hours since they're so dirt cheap. I do see a fair amount of electrode wear. My Lightspeed Plasma II is sparkin' the heck out of those puppies. For $7 every 100 hours, I can rationalize replacing 'em rather than gapping.

My next engine will have 14mm spark plug holes in the cylinder heads, assuming I can get angle valve heads made that way.
 
Yep...no surprise

You had it right Dan, the Autolite 386's are what were recommended to me. I just don't like the adapters and if I can ditch 'em I'll probably save almost 1/2 pound (I put that in there just for you since you inspired me to save weight where I could). The Autolite 386's were 2.04ea at NAPA.
 
Bob Brown said:
You had it right Dan, the Autolite 386's are what were recommended to me. I just don't like the adapters and if I can ditch 'em I'll probably save almost 1/2 pound (I put that in there just for you since you inspired me to save weight where I could). The Autolite 386's were 2.04ea at NAPA.
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I'm not sure the difference is weight is real since the 18mm plugs would be heavier. Also Dan, is it possible to have a cylinder head made to your spec? I've never heard of a 14mm Parallel valve head, much less the more rare, angle valve.
 
I had one go bad

Flying along and the intercom got dreadfully noisy aroung 100 hours....Replaced the plugs and all was well...I get them for 1.18 bucks around here.

Frank
 
ECI will/can do 14mm for top plugs... beefs up that boss a bit as well... not sure if it applies to angle valve stuff..
 
I read a while back that Lycoming will be (if they're not already) offering cylinder heads with 14mm spark plug holes. I googled for it and found this: http://phx.corporate-ir.net/phoenix.zhtml?c=110047&p=irol-newsArticle&ID=957783&highlight=

I think ECI might offer a 14mm option as well. http://www.eci2fly.com/exp/FAQ.aspx

I go back and forth. At times I think the 14mm cyl heads would be great, simpler, stronger, etc. Other times I think the 18mm setup is most versatile and doesn't close any doors.
 
Just a thought

Does one need the 18mm hole for borescope inspections or is the probe small enough to get in through a 14mm hole?

Frank
 
60 hrs on a set of .035 gapped champions and all look great with two p mags running 25 degree timing and a mix of auto and 100LL.
 
My apologies for resurrecting an old thread, but I think this is useful information for those running automotive plugs:

If your radio starts getting ignition noise, make sure you clean and put a light amount of dielectric grease on the plugs/inside boots. Thinking it was the plugs that were at fault, I was replacing them every 100 hours - since I used dielectric grease the problem has not recurred, even with several hundred hours on the (now iridium) plugs. At annual I clean and regrease them, even though the noise in the radios is still not present.
 
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