Re: Henry's 37 Limousine

Posted by Owen_Dyneto On 2017/4/26 8:11:10

I know a lot of folks had their 10mm heads drilled and tapped for 14mm spark plugs "in the day", but I question if you really want to do it. First of all, 10mm plugs of proper heat range for your engine are available over the counter. Secondly, the threaded portion of the head with 10mm plugs is thinner than with 14mm, as the thread length of 10mm plugs is less. Thus when drilled and tapped for 14mnm you will have a portion of the 14mm plug threads protruding into the combustion chamber. These will get carboned up and make removal difficult, possibly stripping the threads in the process.