loucrane wrote:Bill,
There was recent discussion of the NVA for the Sportsman .098, which had the same needle as the larger McCoys. It is possible that the same 2-56 thread would fit the McC .049 diesel...
Hi Lou,
Thanks for the info.
The McCoy .049 needle valves are definitely smaller than 2X56, but I don't have a screw pitch and diameter gage to verify the actual size.
The only non-metric threaded brass stock (smaller than 2X56) that I've been able to locate, is the #1X72 that I mentioned in a previous message. Seemed about the right size for these needles.
The single Atwood Signature needle valve that I have, fits my McCoy .049 diesel perfectly in length, diameter, and taper, as well as the knurled knob on the end. Leads me to believe that one of those early 1/2A manufacturers made the needles and venturi for several different engines.
The NIP Wen-Mac .049 needle I was given is also the correct thread size, but is a different length, slightly different taper, and is apparently anodized to give it that black finish.
I'm considering a membership in MECA, but having a hard time justifying dues in yet another hobby, sport, social organization.
Reports of early crankshaft failures in the original McCoy .049 diesels (with the square cornered crank ports) have been mentioned, but mine never failed. The Brit pen pal I eventually gave mine to (who made a new contra piston to eliminate the rubber O-ring seal), used it for at least another year that I'm aware of, with no apparent problems. I suspect that under size props, hotter diesel fuels (than the equal parts mix I used), and over compressing were the real problems.
Bill