Vaccuum retard mystery

[Alan Coleman <alanco@sybase.com>]

Hi,  I assume TR6 is remotely like Spitfire.

The top vaccuum hole is carb vaccuum (high on butterfly open) for your EGR or 
vaccuum ADVANCE.

The bottom vaccuum hole is manifold vacuum (high with butterfly closed) for 
vaccuum 
RETARD.

If it's connected the way you say, you are counteracting the centrifical 
advance 
in the distributor and getting little spark advance.

AC