Spark Plugs

N2255D · Post by **N2255D** » Thu Sep 29, 2005 10:08 pm

http://www.factoryengines.com/ Go to the site and click on parts, near the top of the page. They are selling Autolite (Unison) spark plugs buy one get one free. UREM-40E's end up to be $8.95 each. Hurry if you need them as the sale ends October 14th.

Post by **GAHorn** » Fri Sep 30, 2005 1:02 pm

I actually stopped by their shop last Wednesday, Sep 28, (on the airport at Arlington, TX) to purchase spark plugs and found they have none in stock, actually. (I guess you can sell things you don't have pretty cheaply. And in the meantime, get quite a few contact information files on potential customers.) They will order a bunch and as they get them in stock, they'll either ship them to you (if you'll give 'em a credit card and pay the freight) or you can pick them up and pay for them at that time.
If you're still interested, the most common plug for our C145/O300 Continentals: Unison PN UREM40E.

dacker · Post by **dacker** » Fri Sep 30, 2005 9:44 pm

I just got a set of UREM 38s, aren't the 40s hotter and usually used in older engines?
David

zero.one.victor · Post by **zero.one.victor** » Sat Oct 01, 2005 4:42 am

Mine had 40's when I bought it, I've replaced them twice (with 40's).

Eric

Post by **GAHorn** » Sun Oct 02, 2005 12:15 am

Champion REM 40E's are the normally specified plug.

dacker · Post by **dacker** » Sun Oct 02, 2005 12:56 am

Just curious, where and why?
David

Post by **GAHorn** » Sun Oct 02, 2005 1:36 am

The engine type certificate designates which plugs are acceptable for the engine. A wide range of mfr, types, heat ranges is allowed, but the engine mfr and the plug mfr together develop general recommendations.
Champion recommends it as a first choice (with the REM 38E as a second choice) in their chart for this engine. This is due to the relatively low operating combustion temps of our engines, which are pretty low compression/low temp as far as aircraft engines go. (Keep in mind that literally dozens of choices exist for our engines. It's mostly a matter of selecting a mfr which is easily available, and the proper heat range plug for the engine and type operation. With Champions, the higher the number, the hotter the plug. (The slower it sheds heat from the plug to the cylinder head.)
The rest of the nomenclature addresses harness set-up, thread depth/length, weather-proofing characteristics, etc. etc.
But if your 38's are operating fine for you, don't just throw them away. IF you're not getting lead and/or oil fouling, then run 'em 'til they drop.

An excellent article (mostly copied from the Textron website) regarding heat range of spark plugs is offered by Sacramento Sky Ranch, at:
http://www.sacskyranch.com/eng23.htm

dacker · Post by **dacker** » Sun Oct 02, 2005 3:46 am

Thanks George. I actually only have about an hour on the 38s, due to my engine run in and test flight today on my fresly overhauled engine. I installed Slick magnetos as I was tired of dealing with the Bendix AD's. When you order you have a choice, my mechanic recommended the colder plugs, in hind sight maybe I should have gotten more opinions. I had 40s before. It doesn't sound like this will cause problems, I still have a set of 40s with only about a hundred hours on them, maybe I will run the 38s and switch to the 40s next. Will the harness set up make any difference?
By the way she ran smooth as silk, I overhauled with Titans ( it was a complete rebuild), newly overhauled carb, new mags, overhauled prop, new risers, new tail pipes, had the entire exhaust system inspected and fitted, repainted all of the baffling, new seals, rewired anything that hadn't already been rewired, replaced the fuel line, oil pressure line, and various and sundry other parts. This all started when I was doing my annual last October and got fed up with the many bandaids that were beneath the cowl.
Needless to say I am looking forward to flying it instead of working on it.

David

Post by **GAHorn** » Sun Oct 02, 2005 4:12 am

Not sure what you mean by harness set-up. If the harness you have fits the plugs...then I'd say no. It makes no difference.
Of course, originally the set up was for the left mag to fire lower plugs and right mag to fire uppers. Some folks have changed that setup and arranged the harness such that the load upper/lower is shared by the two mags. This is an error due to magneto timing.
The reason the magneto timing is not identical left/right is in order to accomodate the fact that one mag fires the upper and the other fires the lower set of plugs. (This was once explained to me ....it had to do with flame propagation....and that's about all I recall about that issue.)

dacker · Post by **dacker** » Sun Oct 02, 2005 3:21 pm

I'm not sure either.

When I ordered the mags the sales person said that I had to specify the plugs in order to get the right harnesses. I don't think she was correct. The mags are set up for one to fire the top plugs and the other to fire the bottoms like the originals. I would think the STC would have to follow the method that the engine was designed for.
I wonder how the heat rating of the plugs affect the problem some have with valves sticking? Anyhow thanks for the info.
David

Post by **GAHorn** » Sun Oct 02, 2005 6:55 pm

In the Champion nomenclature, the leading alphabetical letters designate the type of connection to the harness, and the type of plug. (I.E.-size of harness-nut - whether or not the connection is weatherproof or not, // and whether or not the plug contains a radio-suppression resistor - length of thread-depth.) If your harness screwed onto your plug then your harness is "correct" enough. The only other important choice regarding harness involves the individual lead-lengths, and the connection to the magneto. Doubtless your magneto connection is correct. Leads which are too short won't reach the plugs and leads too long will require the excess be coiled up/stored/shortened.
The STC by definition does not follow all the requirements of the original engine installation. (If it was exactly the same as original, then it would probably have been produced under a "PMA" and no STC would have been required. The original harnesses for these engines may have involved the older type "cigarette", ceramic plug-ends, and hard-elbows. They also may have involved other material differences. Most modern and "after-market" harnesses usually involve "silicone" covered wiring and braid without elbows. Some harnesses (neither original equipment nor OEM supplied) may be STC'd simply to cover all the bases involved.
In any case, the sales person who took your order needed to know the type of spark plug you intended to utilize in order to determine which size connection-nut your harness needed, (weatherproof or not).