Wanting to set/check the timing on a 1973 2.0 liter. Per my manual, it says the advance should be at 27 degree BTDC at 3500 rpm. There is supposed to be some marks on the fan, white is at 0 degree TDC and a red mark at 27 degree BTDC. At idle, is there a certain number BTDC it should be at?

The PO replace the original distributor with one out of a 1.9 liter water-cooled vanagon. This version is the one that rev's higher, the advance curve is more aggressive and the angle of advance is changing over a border range of revolution (vacuum AND centrifugal advance) than the original distributor. The distributor also has the VW OME hall sensor or opto electronic sensor and electronic ignition module so all the points etc are gone.

So I am wondering if this impacts the timing? Was thinking I’d simply run the engine at 3500 rpms, plug off the vacuum advance line, and using the timing light, make sure the 27 degree BTDC mark is lined up with the timing marking tab. If not, rotate the distributor till it does.

Is that about right?

the mark is on the fan up front, not the flywheel.
Look inside the timing hole and you can see the V cut out of the fan housing...that is the mark you are aiming to line up the timing mark into.

You would turn the distributor, not the differential.

Otherwise, yes you are right.

rich

thanks for the corrections - was multi tasking......