Find Type 4 Timing Mark

by Richard Atwell
(c) Copyright 2005-2011


Sometimes you can't find the timing mark on the fan or there are too marks to choose from. Here's the definitive way to determine where the mark should be.

Finding the Mark:

There is an article on called 1972-1979 Type IV Engine Bus Timing Marks by Steve Dolan to help you find the timing mark. The photo isn't perfectly clear so I decided to mark it up. Notice that we are using the bolt on the pulley that lines up with the cutout in the center:

measure to the mark

If you've ever separated the fan from the pulley you need to know which way it goes.

fan and pulley

The first step is to find the key (index) on the back of the fan. It's the extra hole between 2 of the three mounting holes. Almost exactly in line with that key will be a nut on the pulley side (because of the camera perspective they appear out of line but keep in mind it is the closet nut anyway).

42mm clockwise from the exact center of the bolt is the timing mark notch.

bolt relative

At the bottom of the photo you can just see a zero marked on the fan which is clear in the next photo.

This mark aligns the crank TDC with the case parting line. You cannot see this mark unless you've got the style of fan shroud like the 411's and 914's do that require an overhead view to set the timing. Our buses only need the timing scale. The early fans also have a long RED mark on the side past the zero. This is the D-Jet 27 deg. BTDC mark for timing the engine dynamically on those models.


Timing Scale Improvements:

dowel timing

To improve its visibility and your ability to set your timing with a strobe light do the following:

The ease of adjusting your timing is now a night and day comparison. If you've ever had to guess the timing, chances are high your bus is suffering unnecessarily when $20 of parts and a little effort could easily cure it.



04/14/05 - Created
09/07/11 - Fixed broken photos, added translate button, updated footer