Hi all,

my question centers on "is it worth it" on converting a glow engine to gas; Also I am interested in smaller engines/planes and want to actually reduce the power, increase the prop size compared to smaller engines, lower the idle so that the idle thrust is comparable with that of smaller engines. Now I have vintage and replica spark ignition engines and unless I got it totally wrong the spark ignition gives you better contol over the timing and hence all the above and better running, more reliable too.

Yet you say that glows idle better and the main advantage is that of fuel costs; in my case the smaller engine doesnt really use all that much fuel to make the conversion cost effective. So is it still worth it?

To explain my case;-
I have a well used Magnum 180 glow motor (I got it cheap, but it has many hours left on it, good compression anyway), its way to powerful for the smaller planes that I prefer; but not too heavy since substantual noseweight is often needed. Whilst I can throttle down, its lowest idling speed would still be too high, and uneven.
So I am interested in converting it to spark ingnition without awkward machining operations such as a conventional contact points conversion would require.
A Hall effect ignition system looks to be possible, the extra weight is not very significant as my idea is to use this on large slow models.
In fact what I want to do is to lower the revs and power of this engine (and corresponding lower idleing) so as to fit into planes normally fitted with a 90 2st (and with a lot of nose weight!) such as WW1 biplanes. It would of course be able to swing a much larger prop than the smaller engines, particularly with the controlled ignition that spark ignition allows; the revs would be much as for a chainsaw type engine I expect < 8k.

I can fit a small spark plug (a V2 or V3) into the same hole as the glow plug; or increase the hole and thread for 3/8 "V" plug if need be these being the standard vintage spark ignition sizes for 19 to 99 sized motors. Would the usual 'big gas engine' spark overwhelm this size of plug?
I can alter the HT lead, and fix the magnet and sensor without much problem I think,
the thing is would it work? and would it be practical or worth while?

As to the oil question. For spark ignition on the .29 to .60 the argument is the reverse of what I am reading here; 3:1 gasil ratio and only reduce the oil to 25% if plug fouling is a problem. The lubrication is obviously adequate, the extra oil cools the engine by carying away the heat in the exhausted oil. Btw, Colemans white gas is prefered over pump gas due to unwanted additives in pump gas

So why do the two fields of opinion differ by so much? is there an easy answer
I am not familer with engines larger than .60 2sty, so this is all new to me. My cheap 180 was a way to enter into the fun without too big a plane (if the thing could be tamed)

?

cheers

Jim