I would keep the phenolic? insulator if at all possible. Nissan thought it was needed for the stock carb although the Weber may not, I just don't know. If making gaskets get extra thick material. Don't forget to use Loc-Tite on the adapter studs.
Take the little rubber cover plug off the middle and turn the screw anti clockwise to reduce the sensitivity of the BCDD.
The BCDD is turned on by high intake vacuum when decelerating. Normally the mixture goes so lean that is doesn't burn. The BCDD is a little mini carburetor within a carburetor that opens to supply gas and air during this time. When vacuum returns to normal is it supposed to shut off but sometimes it doesn't and you have a slight runaway idle. If this fixes the problem then this was the problem.
The bright links are only for the initial placement of the chain and sprockets. As soon as the engine is started the bright links become random and line up maybe every 20 turns so don't go by that.
Set TDC exactly* and only by turning clockwise. If you over shoot don't just back up, but back up 1/4 turn and try again even if it takes a dozen tries.
*This is absolutely critical so use the notch on the crank pulley and the timing scale for ignition.
There is no TDC mark on the Z series head for cam sprocket checking so what I do is look through the top hole in the sprocket and directly between the two rocker arm towers for a small vertical casting mark...
The back of your cam sprocket should have a V or U notch in it. Confirm that the V is below or perhaps just slightly to the right of the line and NOT to the left of it. Like below...
I'm thinking of incorporating a heat shield on my build. It's an L20B, and now has a Cannon intake with dual Webers. Just resourcing a smaller diameter b/booster for better fitment, air filter clearance is the issue here. Any ideas regarding which heat shield to use with said configuration?