Timing mark mystery, Please help me solve |
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Timing mark mystery, Please help me solve |
bbrock |
Dec 29 2018, 05:54 PM
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#1
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914 Guru Group: Members Posts: 5,269 Joined: 17-February 17 From: Montana Member No.: 20,845 Region Association: Rocky Mountains |
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) |
bbrock |
Jan 3 2019, 12:25 PM
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#2
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914 Guru Group: Members Posts: 5,269 Joined: 17-February 17 From: Montana Member No.: 20,845 Region Association: Rocky Mountains |
If you have another fan handy can you compare the location of the 0 TDC mark ? I don't know bus motors but if the fan housing had the notch in a different spot the TDC and 27 deg mark would be correspondingly different. (IMG:style_emoticons/default/confused24.gif) I had forgotten about it but yes, I do. Next time I'm out by the storage shed, I'll take a look. Ljet and Djet have different timing marks. The fan probably came from a different engine. That's why you have different markings. This seems most likely. What's weird is that I've had 3 1.7L engines from 914s with D-Jet, 1 2.0L 914 with D-Jet, and a 1.8 engine from a '74 Bus. The bus engine is chief suspect for a donor fan but I think that bus was originally carburetor and they didn't start using L-Jet until '75. Maybe that is wrong and my bus was originally L-Jet. I don't know much about buses other than I loved mine. Did they maybe start switching to L-Jet in late MY 74? Or maybe someone had already swapped fans on any of the other engines before I got them. Sounds like one thing I should do is verify that the TDC mark on this fan is actually TDC. |
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