>   A critical fit someplace?
>

I remember mention of one critical fit issue, and since I haven't
opened my combustion chamber and seen it myself, it might not apply.
But it might, so here goes: the flame orifice is not intended to
stand directly below the heated area, but rather in such a position
that when the NORMAL flow of air is being pulled through the
combustion chamber, that the tip of the flame is distorted by the
airflow to be positioned under the heated are.

Just offering in case it could apply.

Jim