4Cruisers
SILVER Star
After putting the project on the back burner for a while, I recently took a fresh look at converting a late F engine vacuum retard distributor to vacuum advance. This morning I wrapped up the project successfully .
The approach I took was to modify an early 2F vacuum retard advancer so that it could be a direct physical replacement, with no modifications to the distributor itself, and to closely match the advance curve of the early F engine advancers. I had two good used retard advancers from 1/75 through 8/76 19100-61020 2F distributors and another in non-working condition. I cut the bad advancer up to determine what limits the actuator rod travel to ~2mm. It turns out there is a nut on a threaded shaft inside the outer can that can be backed off to allow for ~4mm of actuator rod travel, which equates to ~10.5 degrees distributor advance. I replaced the internal spring and adjusted its length until I arrived at the vacuum advance curve shown in the attached comparison plot. I then cut the J-arm off the F engine advancer and secured it to the shortened 2F advancer actuator rod.
When vacuum is applied to the vacuum nipple, which is on the inboard side of the diaphragm, the diaphragm pushes the J-arm against the stud on the breaker plate, rotating the breaker plate CCW and advancing the timing.
Here are photos of the prototype advancer and a plot comparing the vacuum advance curves of the modified retard advancer and the advancer (19220-60072) found in the early F engine distributor 19100-60042.
The approach I took was to modify an early 2F vacuum retard advancer so that it could be a direct physical replacement, with no modifications to the distributor itself, and to closely match the advance curve of the early F engine advancers. I had two good used retard advancers from 1/75 through 8/76 19100-61020 2F distributors and another in non-working condition. I cut the bad advancer up to determine what limits the actuator rod travel to ~2mm. It turns out there is a nut on a threaded shaft inside the outer can that can be backed off to allow for ~4mm of actuator rod travel, which equates to ~10.5 degrees distributor advance. I replaced the internal spring and adjusted its length until I arrived at the vacuum advance curve shown in the attached comparison plot. I then cut the J-arm off the F engine advancer and secured it to the shortened 2F advancer actuator rod.
When vacuum is applied to the vacuum nipple, which is on the inboard side of the diaphragm, the diaphragm pushes the J-arm against the stud on the breaker plate, rotating the breaker plate CCW and advancing the timing.
Here are photos of the prototype advancer and a plot comparing the vacuum advance curves of the modified retard advancer and the advancer (19220-60072) found in the early F engine distributor 19100-60042.