Connecting up the primer with 1/8 inch stainless tubing starts with the fitting on top of the fuel filter.
First install a fitting into the 1/8 inch pipe thread in the top of the filter housing. This can be a straight fitting, a right angle fitting or a 45 degree fitting, depending on how you plan to route the tubing up to the primer.
Then there is a similar fitting in the inlet side of the primer.
Then another fitting on the outlet side of the primer and a tube leading up to the primer header which is fastened to the intake tube of cylinder #1.
From the header there are four tubes leading to the primer input fittings on cylinders #1, #2, #6 and #7.
In selecting the fittings that have a 1/8th inch pipe thread and an end that receives the primer line tip, there is a potential trap.
Below is a picture of four fittings to choose from. At the top are two 90 degree elbow fittings and a 45 and straight at the bottom.
The two right angle fittings look alike, but definitely are not.
One is a primer jet, with a very small hole, (about .010) that only goes into the cylinder head, and the other is used for installing the tubing from the filter housing to the primer header.
Using the primer jet in any of the fuel suction lines or between the primer and the header is a sure road to a poorly performing primer.