Dave , What I would try first is a sharp probe or screwdriver to see if there is some build up in the hole . You might also remove the gland nut to get at any build up easier . I have had both the longer bulb and the shorter bulb in my cylinder head and they have both worked fine . There is usually some build up around a bulb that has been installed for a while , so perhaps you have some build up farther back in the hole . Then again , you might just have a VERY long bulb of either like used on some tractors . If you can measure your bulb of ether , I can tell you if I have used one as long .