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All is well that ends well! Due to hard-starting, especially hot, from failing aging coils, I replaced my aging Eisemann magnetos and non-shielded wires with brand new Slicks and Slick shielded harness, as well as spark plugs. My airplane does not have cowl bumps, and wanting to avoid them, and still enjoy the ability to use a hand-held radio without too much RF intereference, I ordered "Ercoupe" cups from Fresno Airmotive ($79.00 with shipping). They are intended to be used with C-26 or M-42 spark plugs. Problems: As known beforehand, thanks to forum members, the cups need to be cut down and rethreaded. I know several guys who work in machine shops, etc. They couldn't set up for a small run of four pieces within a reasonable time frame, needing to change to a 4-jaw chuck to start with. So, I ordered a threading die from the only known source, McMaster-Carr ($62.00 plus 6.00 shipping) and I purchased a hole saw 3/4" size and mounting mandrel ($18.50 w/tax), and used a Dremel tool to remove inner-;rotruding teeth and get a 5/8" exact OD. I always wanted a drill-press vise, so bought one ($52.50 w/tax). With fingers crossed, and holding my breath, I cut off the old oversize threads with the hole saw; all went well (except for some inpromptu shimming requirements, the little spark-plug attachments weren't all welded on at a 90 degrees angle). Then, they were ready to install, BUT the spark plugs I had, model M-41's wouldn't fit into the recess in the bottom of the cups, the o.d. of the plugs being about 1/16" larger than the i.d. of the recess. I was "told" by an "expert" the cups were made for the old C-26's; I found a guy with new old stock for $18.00 each, ordered four. They wouldn't fit either, same diameter as the M-41's. Only recourse is to machine the recess 1/16" larger to allow the plugs to seat to the bottom. Now I really need a machinist's services; they're still busy, so I waited a couple days to have the job done. Now all is installed, and success! The engine starts easily when warm, indeed with throttle at an idle, moving the prop as slowly as possible, when the coils fire the retarded magneto, the engine chugs immediately to life. And the radio noise is all gone, even allowing a quite comfortable use of the intercom. With a new external antenna, I can hear and talk to gound stations line of sight to very considerable distances.
I figured anyone else considering this mod might be interested to know that it works, but all is not as simple as it might be.
I figured anyone else considering this mod might be interested to know that it works, but all is not as simple as it might be.
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