Yes they can-as can all the Cox heads from 049 up-BUT-you will lose a degree of performance from a combination of reduced compression and less optimal combustion chamber shape. You lose volume around the plug threads and the element recess in the plug itself. Optimising the drilled and tapped head will require testing with a variety of different brands and heats of standard glowplug. [how much time effort and money do you want to spend doing this?]Commercial head adaptors to take a standard glowplug are available for a number of engines-Cox 049.09/15, Holland Hornet, Norvel 049/061/074 and Testors-McCoy 049. MECOA makes one for the Cox 09-part # 911-046-price is $13.99 [then you have to add the cost of the plug]. A few suppliers-such as Bob Mattes (
www.flyfreeflight.com) will machine your burnt out head to take a Nelson plug, in which case you may not see any performance drop-and in some cases an increase. Ebay vendor cox_hyper_speed lists several adapters for several sizes of Cox engine (and Norvels) for either standard or turbo plugs-but has no listings running at present. Or put another way-there's no such thing as a free lunch-and it may be less aggravation and hassle to buy new 09 glowheads!
IF you are burning out Cox heads on a regular basis then you are doing something wrong..................
ChrisM
'ffkiwi'