Originally Posted by
jayd3
I've seem lots of converter heads so you can use a regular 1/4 -32 glow plug but which one is good?
None of the conversion heads are any good, it is as simple as that.
(they can be reworked if you have a lathe, but will never perform as well as the heads with integrated glow wire)
Merlin inserts are possibly the easiest source nowadays. They are high compression ratios though so you will need a few extra head-shims.