Timing mark mystery, Please help me solve Options

[bbrock]

Cleaned up the impeller on the 2.0 liter today and need to repaint the timing mark. To my surprise, I found two marks to choose from (IMG:style_emoticons/default/new_shocked.gif) The mark on the right (nearest TDC) was cut with a file and is exactly 52.5mm from the center of the "0" for TDC. According to Haynes, that is the correct distance for 27 degrees BTDC. The farther mark looks to be original and is about 57.25mm from TDC. If Haynes and my math are correct, that would be around 29ish degrees BTDC.



Now I have a vague memory of cutting a mark on an impeller of one of the five Type 4 engines I've worked on, but too much alcohol has swashed through my brain in the 35+ years since that event could have happen to remember why. I can think of two reason: the original had a broken fin and I stole this one from a bus engine, or I just put a mark in where Haynes said it should be, assuming the other was wrong.

What really bothers me is this image from another thread has a pic with 27 BTDC marked exactly where my original mark is not at 52.5mm where Haynes says it should be, but TDC in that pic is not where mine is using the impeller blades as a guide. So can anyone help me figure out which frickin' mark is the right one? Is Haynes wrong? If it is the one I cut, any idea why the other one is there? Did buses have a different mark? So confused. (IMG:style_emoticons/default/confused24.gif)

(IMG:http://www.914world.com/bbs2/uploads/post-8384-1196294703.jpg)